The Danger Zone

Otter Z5 Kettle Thermostat Repair

2022-08-29T21:00:00.002+08:00

Had one of these on a limited edition Hello Kitty Tefal Mini (BF8120 is the model I believe). SWMBO decided to dig it out of storage and found that it kept boiling the water without ever tripping the thermostat normally.

Externally about the only thing that felt wrong was there was no tacile (clicky) feeling when the kettle’s boil switch is actuated. Suspecting the thermostat to have internally welded itself together, I took it apart.

The handle section disassembles with 2 screws on the inside under the lid, once those are removed, there is just enough flex in the plastic to remove the lid and the internal steam manifold section to access the thermostat. A single screw holds the thermostat in place, once that is loose, disconnect the 2 wires taking note which wire goes where (this is just so during assembly, the wire’s don’t twist around and cause issues with the plastic going back together, electrically I’m sure it’ll work just fine).

The entire thermostat looks like this.

Filpping it over, the bimetallic disc is visible, using a sharp tool to dislodge it off the catch, the disc slides off.

This is the pin that disengages the contacts internally when the steam is hot enough to bend the bimetallic disc, once the disc is off, the pin can be shaken/gently persuaded out.

Next the 2 catches on the outer edge, near the electrical connections, can be pushed in and the assembly slides apart. I broke the catches during removal but that’s not a big deal, the securing screw will still hold everything in place when the thermostat is screwed back into the kettle.

Here I’ve gently wire brushed and polished up the contacts with a fibreglass pen, mine were welded closed and the this contact had lost the ability to let the actuating lever cam over and hold the contacts closed, some adjustment later on the hump section of this contact fixed that (I had to bend the hump section up slightly as well as pull on the tab that engages the lever, essentially lengthening the hump section, for a more tactile response). Test often during adjustment and go slow, it’s easier to correct a small error/wrong adjustment.

Once satisfied with the feel and after cleaning the contacts up, I pieced it all together and gave the kettle a spin, which confirms it works good again. Hopefully it’ll stay that way for good long time.

Kenwood KA-691 repair

2022-05-15T07:39:00.001+08:00

Unit received in fair condition, front looks good, no deep scratches or missing paint, rear and bottom has very slight corrosion.

Unit will not come out of standby mode, cut bottom chassis for service access, found no issues with main amp board.

Powering up microcontroller (front panel assembly, MCU is a M50941-597SP), was able to get some response from VFD with CD DIR depressed. Leaving it powered up for a couple minutes does eventually result in normal amplifier operation.

Took the chance to check output offset (negligible) and re-adjusted bias for 18mV per service manual.

Pulling power off and allowing amplifier to cool, will mean the next round of power up will take minutes for amplifier to come out of standby, verified clock to MCU is correct and started, Vcc and AVcc were correct and present, tried external 5V regulator, changing input filter caps, trying a quartz 4Mhz crystal instead of original resonator, to no avail, slipped DMM probe and shorted MCU pin from -35V (VP/VFD bias voltage) to adjacent input pin (38 shorted to 39 or 37). MCU now real and truly dead (heard a small pop and immediately shut off the amp by pulling power cord out).

Opps, killed this little sucker.

Was unable to located MCU (PN M50941-597SP or M50941-589SP) even through obsolete component brokers/traders. Decided to cannibalize from another unit (got off eBay USA).

Rear inputs slightly polished to assure good shield contact, input board was removed for visual inspection.

Re-soldered power input board where joints showed signs of crack formation, re-soldered main amp board as well.

Cracked and oxidised joints on main PCB.

Reworked these

More inadequate joints

Main PCB cleaned up after rework.

Signs of cracking on transformer ribbon

Joints reworked

Reworked one joint on transformer input.

Service access panel flipped and re-attached with M3 washers and screws.

Speaker A & B switches cleaned and lubricated.

Ebay amplifier arrived in broken condition (likely due shipment damage, tone control’s smashed, power button smashed, will not turn on), returned.

Seller agreeable to sell just the front panel PCB for parts, procured front panel PCB alone.

PCB arrived, wrapped in aluminum foil and plenty of bubble wrap for ESD and shock damage resistance, front power switch PCB area found cracked and power switch pushed in.

Crack stop drilled and PCB trace patched.

Epoxy patch on front of PCB.

ESR measured on all front panel PCB capacitors. Qty 4 were replaced as follows

Designation	Original values	Installed values
C80	220uF 6.3V Low Profile	220uF 10V bent over
C92	220uF 6.3V	220uF 10V
C89	10uF 50V	10uF 50V
C83	10uF 35V	10uF 50V

Power switch desoldered, new power switch soldered, cracked PCB trace patched over with enameled wire, crack stop-drilled with 1/16” drill bit. Solder side PCB lightly sanded and epoxy applied over cracks, top side sanded and a small patch applied with epoxy as well.

Power ribbon pads on front panel PCB slightly damaged during removal (qty 3), post soldering power ribbon connection, extra 3 enameled wires were used to jumper over to the ribbon connections and held down with Dow Corning 3145.

Jumper wires on front PCB

Unit tested and verified to power up instantly upon application of wall power.

O2 Headamp output board, OPA1688s Part II

2022-04-25T01:59:00.001+08:00

It’s been awhile since I’ve had an update on this project, I actually completed it, but never got around to documenting everything.

Drew up a schematic and layed out a board, JLCPCB fabricated it with no issues. I used some existing board images that AGDR made available, so mechanically it’ll fit and clear whatever the O2 has existing on the board.

A set of 2 mil-max pin headers are used to interface to the existing opamp sockets, and then a couple of jumpers are required to tap onto the existing O2 board (ground, signal ground and lastly for the battery voltage comparator).

Each channel again is a bunch of OPA1688s paralleled (see previous post here for details) The Danger Zone: O2 Headamp output board, OPA1688s Part I (fillwithcoolblogname.blogspot.com)

Here it’s partially assembled, I use liquid flux (that’s kinda messy). Everything gets dunked in my ultrasonic cleaner afterwards though so I’m not worried.

View of the rear, there’s an output relay that latches and prevents that annoying O2 issue of dropping in and out when battery levels get low and creates that popping noise (which is probably not good for your headphones).

From the front assembled, here the signal ground jumper is visible.

Top assembled, here the comparator jumper is visible.

Last jumper for power ground, straight to the battery holder.

Offset voltages measure pretty good.

I stacked a whole bunch of capacitors on my breadboard to do some random capacitive loading tests (with a ~33ohm) load, it performed admirably (I can’t exactly remember the numbers, I think it was 2nF or so load capacitance with 33Ohms, typical headphone cables are maybe 30pF per foot, so this is plenty stable).

Finally this is it all assembled and cleaned up.

I haven’t gotten around to putting the schematics and board diagrams anywhere. If somebody is interested I’ll get off my ass and do it. Myself I’m fairly interested in what this measures properly in terms of THD+N, but I don’t have access to any cool equipment to do it.

Spectra S1+ Not Charging Battery

2022-04-16T06:40:00.001+08:00

Had another unit to mess with. This will not charge it’s battery, upon power on with the charger/adapter, the battery icon blinks empty continuously for abit, before it gives up trying to charge the battery.

Turning the unit on without the adapter, the LCD will come up for 1 sec, then shutoff.

Took it apart, battery looked fine, voltage measured ~11.1V and stable (I thought it was dropping out when the pump was commanded to run), pulling the pump and solenoid connector off and trying to run the unit with the battery, exact same behaviour (shut itself off after 1 sec).

I then turned my attention to figuring out how the microcontroller on board measures battery voltage, found a resistor divider and a little output capacitor just to the right of the microcontroller (R36, R38 and C35R).

Measuring the top (input from battery) and turning on the unit from the front panel (fiddly yeah), I only measured ~8V (when it should be ~11V), somehow full battery voltage was not making it through. The input is not applied to the divider all the time, only when the micro commands the unit on, does input voltage appear thru the action of Q12, Q11 and Q9.

Probing around Q12, Q11 and Q9, I couldn’t find anything wrong with them. I ran a jumper from battery voltage to the input of the voltage divider and verified the unit works as it should, next I shifted the jumper to the input of Q11 and once again verified that the unit works (will accept charge, will turn on and stay on with battery power).

This was when I realised there might be some broken trace or via from battery voltage to Q11.

Flipped the PCB around and removed the LCD+plastic support.

Looks like some fluid damage under the Down switch.

I removed the switch, cleaned the mess up and found that a via leading to the other side had broken, there’s no good way to patch that via (since it’s so small) and I opted to keep the jumper on the component side. Didn’t take a picture of the completed patch, but it looked like the original jumper I put on, except tucked neatly away and the battery voltage tapped from closer to the battery connector (after the ferrite bead from the charging section).

Reinstalled everything, charged the battery and tested it out, I can confirm everything is working as it should.

Spectra S1+ Repair

2022-04-09T07:00:00.003+08:00

Received one that wouldn’t turn on even with the adapter plugged in. Unit opens up with 4 screws removed from base.

Quick check found the main power rail shorted, initially I thought it was a shorted TVS on the input, removal of the input TVS didn’t fix that, so I started looking around, that’s when I found a small burnt area on the PCB.

Towards the left is the burnt out component, nearby is a NCP3063, as far as I can make out it’s a boost converter (I didn’t know initially what it does until later). I couldn’t de-solder the FET normally as it had fused itself to the PCB track when it failed. Applying heat and leveraging it off the board the copper it was soldered onto de-laminated from the PCB itself. Luckily the source and gate pins came off the PCB ok (just the drain pins were affected).

As far as I can tell, the SMD markings point to the FET being a NTGS4141N (S4 marking code, 7 date code).

With the FET removed (I cut the dangling bit of the PCB off with a scalpel), I could actually power up the unit with the adapter plugged in (yeah!).

I then decided to check if the FET driver and NCP3063 were at least still operational.

Hooked up some insulated magnet wire to the drive to my oscilloscope.

That verified it was still working, also during this time I saw the drive only come on for a couple secs during initial power up, my guess is it’s used only during battery charging (the pack is a 3S 11.1V nominal battery, so it needs ~12.5V to charge it fully when the adapter only outputs 12V, and charging is done through a MAX1873, which I guess needs a couple of volts headroom to charge to ~12.5V)

Scrounging around in my parts bin I found a NTP18N06, which is fairly similiar in terms of drive requirements, but a little higher Rdson (90mOhm vs 21.5), since I had lost part of the PCB I figured the exposed TO220 package would probably be best for heat dissipation and there was ample room on the PCB to mount it on.

Yeah, the size/packaging difference is huge.

A quick solder job and viewing the drive on the oscilloscope + output voltage measurement, verified nothing was wrong, no smoke and the boost circuitry output voltage was present (~14.5V or so for a couple of secs, I tried hooking up the original battery pack to see if it’ll start charging and let me test this section for longer but the pack was too far gone).

I scraped off a bit of PCB on the ground plane, flipped the TO220 package around and soldered the source pin directly to the FET, ran some insulated magnet wire to the inductor and gate pin on the PCB, held everything down with Dow Corning 3145 (electronics safe RTV).

Next I turned my attention to the battery pack, which had a bloated LiPo cell, I couldn’t source an exact replacement 3S battery pack (it uses a built in BMS to balance the charge, there are only 2 wires coming out of the pack, so non of the usual RC type LiPo packs with external balance connectors will work safely, at least not without wiring up a BMS on it). I removed the bad cell from the pack and clipped a random partially charged 18650 to it, attempting to charge it the battery came back to life (the BMS had stopped any voltage from coming out the pack with the 1 bad cell)

Got my hands on 3x new Molicel P26A 18650s and I decided to keep the original BMS.

A bunch of spot welding and soldering later, I’ve got a working battery pack with the original BMS.

Here it is in it’s original spot. I’ve elected to tape the original labels within the machine in case somebody/someone else needs to know what was in it originally. With these new cells, I’ve verified it’s able to charge and stop properly, (cut off at 12.5V) and it should last a bit longer given the capacity has now increased (original 2000mAH, now 2600mAH).

Finally, I re-soldered the input TVS diode and closed it all up. 😁

Mackie CR4 Repair

2022-02-12T06:05:00.002+08:00

Over the years I’ve replaced all their internal capacitors, changed out the 12V zeners in the regulator area for beefier units (the stock ones are down on the PCB and keep dumping heat into what appears to be cheap PCB material, it’s definitely not FR4, I tried mounting them off the board to give it room to dissipate the heat), also had replaced the L-R switch and scrapped off all the nasty glue that they used during manufacture that was turning conductive and corroding components on the PCB (I saw a resistor lead almost disintegrate to nothing).

Right now they will come on, but will randomly get muted, I suspect there is even more damage to the 12V regulator area on the PCB and the mute circuitry was kicking in on the TDA6275 (all kinds of guides exist on the internet that just tell you to snip the Mute pin off, it’s not a proper fix as the Mute circuitry ensures +/- 12V exists before unmuting the amp section).

That’s the 12V section, after removing the associated components.

The PCB after I’ve cleared off the tracks that were heat damaged, it’s too far gone to try to patch up. During the process I found a cracked trace on a leg of a zener diode, that was probably why it was randomly muting.

I decided to remove all the circuitry around the +/-12V area, including the components that generate the mute signal and move it all to an external PCB.

The original +/-12V regulation was achieved thru value engineering with the below

The mute was done as below (I’d have to replicate this on my board)

Drew up a schematic and layed out a board. I’ve used TO220 7812 and 7912 for the regulators and all through hole parts.

Here it is populated and installed.

A picture of the clearances and mounting involved (I used a single mount point in between the 2 TO220 regulators, I wasn’t sure the PCB would be ok flapping in the breeze inside the speaker with just the TO220s for mechanical support).

And the rear of the entire PCB when I was done, I’ve marked out where the +/- voltages get tapped for this external regulator+mute board as well as where the +/- 12V regulated voltages go back in. I’ve left the burnt area as is (didn’t attempt to grind them out) but with a sharp scalpel cut off the tracks back to a good area, so nothing is shorting.

Putting it back together, I can confirm they work, time will tell if they keep working.

O2 Headamp output board, OPA1688s Part I

2020-12-14T00:47:00.005+08:00

NwavGuy left us with a fairly well performing, battery powered headamp. I built mine fairly early on when they got out into the wild.

It's been almost 8 years since he disappeared into the ether and in that time, plenty of new opamps have been released which seemingly (at least on the surface) look like a better deal then the NJM4556s that drive the outputs (lower distortion, offset as well as higher output current capabilities).

Nwavguy himself was fairly certain the output opamps were the bottleneck for the O2's THD figures, AGDR attempted an output booster that was based on LME49600s and OPA827s (Around 14USD in opamps per channel).

https://www.diyaudio.com/forums/headphone-systems/244473-o2-headamp-output-booster-pcb.html

Ultimately I feel that the LME49600s were difficult to heatsink properly given the tight internal space. I do indeed think it should provide (at least for a limited time) way more power than the original 4556s were capable of, the headphone mute relay addition is also a double bonus (rid turn on/off thumps and the motorboating thing that happens when the O2 batteries get drained).

Unsatisfied I went around looking at Opamps released fairly recently. There were 2 that caught my eye.

One of them would be the OPA1688, the other would be the OPA1622.

Decisions, 1688s doesn't quite have the capacitive drive, the 1622 is in a tiny package that's a pain to solder and bias currents are ~1.2uA, meaning I'd need another opamp stage in front of the 1622 to drive it properly.

I decided that parallel 2x OPA1688 (4 op amp channels) would be my design choice, my lowest impedance headphones are 32 Ohms and some back of the envelope calculations determined that even at worst case dissipation, the opamps should scrape through and not hit Tj limits. The O2 is/was all about getting performance at a lowish cost, which I think this decision would be in-line to.

External compensation by increasing noise gain to improve phase margin was figured out with inputs from johnc124 for another project.

https://www.diyaudio.com/forums/headphone-systems/293247-opa1688-super-cmoy-2x-9v-real-ground-headphone-relay-pcbs-7.html#post4762471

Power dissipation calcs:

RL = 32R

Parallel 4 = 128R effective

Pq = 24(0.018)

= 0.0432W

Io = 6/128

= 0.046875W

Pdmax = 6(0.046875) + 0.0432

= 0.32445W

Temp rise over ambient = 0.324(116.1)

= 37 deg C (per opamp)

= 75 deg C (per SOIC dual opamp device)

To be continued in Part II

The Danger Zone: O2 Headamp output board, OPA1688s Part II (fillwithcoolblogname.blogspot.com)

Klipsch Promedia GMX 2.1 Hiss & Weak headphone output

2020-10-26T14:57:00.007+08:00

Klipsch made some questionable choices with regards to the amount of gain and how they drive the headphone outputs. Mine had bad volume and sub control potentiometers so since I was gonna dive in and replace those, I might as well fix the hiss and headphone section.

Per the stock design, there's an insane 7.5 gain (just on the headphone section) regardless of where the volume control position is at, even with it off, which just makes the speakers hiss constantly (I can hear them at my sitting position) even with no / grounded inputs, I have never used the volume control past the 1/4 mark.

I've traced out just headphone section (bottom right of the control pod PCB), which is the biggest contributor to this hissing. No idea why they went with output resistors and 7.5x gain, with such a insane amount of output resistance the voltage driving the headphones just gets dissipated in them. I put in 1kHz sine wave and measured ~120mVp-p but only ~50mVp-p on the headphone side of the resistors.

Here's what I did to fix all that. In the course of messing with this I killed the PT2308 while probing around (opps), they're kinda hard to come by in a DIP package, so I was either gonna have to put one on a SMD converter board or put a different opamp in there.

I went with a NJM4556 (which has more output current capability than the original), a gain of 1.5 (which was plenty loud on my headphones), removed and shorted out the 2 output resistors, increased the output capacitors to 470uF, upped the input capacitors to 6.8uF (probably overkill) and changed the feedback capacitor to 150pF (prevents HF from being amplified).

Even with the stock 33pF feedback capacitor, I didn't manage to get the opamp to oscillate. A good test is probably to stick a nice sharp square wave onto the input and see if it's gonna ring a bunch, I might do that if I experience issues.

With the changes in place. I can only hear a slight hiss if I place my ears right up to the speakers and only from the tweeter. I no longer have to only use the bottom 1/4 of the volume control and I get plenty of drive to my headphones. I'm happy, lol.

ECU repair Miata NA8 1996

2018-09-17T17:08:00.001+08:00

Miata NA8 1996 ECU repair, car wouldn't start, swapping in a 2nd ECU and it started.

ECU out of it's case and my trusty DMM.

ECU overview, as far as I can tell there are only 3 electrolytic capacitors.

C006 has developed a nasty leak and spilled some of it's guts on the board.

Cap removed, some of the conformal coating around that area was damaged by the capacitor electrolyte.

I used some alcohol and then a small fiberglass pen to expose the traces under the corrosion. It looks like there's a break under the small trace to the left and the trace on the right is almost gonna break too.

Measuring to find out if it's broken for sure, from that resistor I'm probing with the black lead it goes to 4G on the ECU main connector.

No surprise here it's completely broken, no continuity indicated. I'll go ahead and patch it up later.

All capacitors removed. I used a manual solder sucker, had to add more solder to some places to get it to completely clear out.

New Caps in.

Caps I bought and their prices. I'm lucky there Tanner Electronics near me and they are open on Saturdays. Sweet.

Nichicon and Panasonic caps were used to replace the old.

105 Deg rated caps all around.

Jumper wires in place.

I had to route one wire around the back, as there was no easy way to solder to the ECU socket from the top for it's outermost pins.

Wires held down with small dabs of Dow Corning 3145 RTV. Stuff is electronics safe. Ideally Kapton tape would be a much neater way to do this, but I didn't have any on hand.

ECU back and closed up.

Short summary of what I did on the rear casing. I had to substitute some different voltage capacitors based on what I had available.

Chamberlain/Liftmaster/Sears Garage door opener range issue

2017-08-30T00:09:00.001+08:00

Rental apartment I’m at has a garage door opener that’s been working well up till recently, it would open with the remote but not close.

I’ve been living with that (and jumping across the sensors below that detect when something is in the way) until yesterday it wouldn’t reliably open unless I was up against the garage door (boy was I worried). I was also worried about interference from LED lightbulbs that could potentially be affecting it’s range, turning off all lights resulted in no change so it wasn’t that.

I tried re-pairing (reprogamming) the remotes to my garage door opener (I have 2) and unless I put the remotes up against the opener it wouldn’t pair properly.

Apartment techs came over to take a look and they decided to change out the entire garage door opener (current unit is from 2006 so it’s 11 years old), however procurement will take a while and I’ll be stuck having to use the wall switch (that still works) or the manual pull.

Decided to tear into the logic board to see what’s going on and if I can fix it.

That’s the plastic back that holds the logic board, removal is easy (3 sets of wires for the wall switch and sensor) and 4 screws. Mine is a 41A4252-7G, I suppose quite a few different models of garage door openers from the same manufacturer will be similar. Disconnect one connector and it should be free to move to your workbence, a few more screws hold the main PCB to the plastic back.

Board out, no broken joints like I’ve read on some other places.

http://ths.gardenweb.com/discussions/2382811/craftsman-garage-opener-clicks-only-and-led-blinking-5-times

Decided to remove the main filter capacitor on the input of the 5V regulator (I’ve read elsewhere where someone had a similar issue that injected noise into the RF section and killed reception).

o.O. More than 25Ohms ESR? That’s definetly bad, my DMM had a capacitance measurement that indicated that it’s 220uF (it’s marked 330uF), doesnt seem that bad but ESR was indicative of a failed unit.

A trip to Tanner Electronics nearby got me 5 Nichicon 330uF 35V capacitors for $1.25. Their ESR measures 0Ohms.

Here’s the location of the capacitor.

Board overview.

After soldering in the new capacitor and hooking it all back up. My garage door opener works good again. Yay!

Gameboy pocket LCD backlight + bivert mod + LCD repair Part 1

2016-02-08T08:13:00.001+08:00

This project started with me finding my old Gameboy pocket. It was still working, but the LCD had developed a dark spot in the middle.

Kind of like this one, the picture is not of my gameboy. Booting up games with it results in this.

Looking around for solutions to this issue, it seems like

1. Gameboy pocket replacement LCDs are hard to come by.

2. You could do some really cool stuff now with backlights and biverting (more on that in a moment).

I went ahead and ordered a backlight module off nonfinite electronics (which should come with a spare polarizer).

http://nonelectronics.com/

My thinking was that there was something wrong with the reflective layer or polarizer and that since I would be getting rid of those layers during the backlight mod, all should be good.

I pulled the LCD module out of my gameboy pocket and set to work.

Look at the discoloration on the rear polarizer + reflective layer.

Putting in the backlight module, I realized that the issue was not just contained to the rear layers, the front polarizer on the LCD had also suffered damage (I think the glue has breakon down in the middle spot).

I tried removing the front polarizer, which was fairly difficult. Not only did the front polarizer pull off, another semi-shiny layer of the LCD also peeled in some places as well, figuring I had nothing to loose, I removed everything and stuck on the replacement polarizer.

Eventually after a few hours of mucking around, the LCD did work, somewhat, in the process of doing all of these and trying to remove all residues, I had to use acetone to clean up the LCD, I suspect some of that seeped under the LCD connectors and compromised the connection. I was now missing some horizontal lines.

Next I tried the age old tested method of using a soldering iron to try and re-bond the connections, the Gameboy pocket has a slightly different kind of ribbon cable though.

Even with a fast swiping motion, the whiteish ribbon cable was over-melting and that was the end of my experiment of fixing that particular LCD.

Crap.

Part 2 will follow after I find another Gameboy pocket and pull some parts off it to fix my existing console.

Blogger returned the following error "NotFound: Not Found"

2016-01-01T13:13:00.001+08:00

Using Windows Live Writer and find that you can’t publish your blog entries because of this error?

You’ll get a popup just like the below and then a login prompt will come up, nut even the right password doesn’t work.

According to here:

https://productforums.google.com/forum/?hl=en&pli=1#!topic/blogger/lw_sNsyySKI

Essentially Google has upgraded their authentication systems and because Windows Live Writer wasn’t being maintained there’s nothing they could do about it.

However Microsoft has made Windows Live Writer open source and the team has updated it to work.

Just download the new application here:

http://openlivewriter.org/

It still looks and feels exactly like what Window Live writer was like so I’m not complaining.

Vitamix blender motor repair

2016-01-01T13:08:00.001+08:00

Windings on motor rotor were damaged, I think the chaffing on the insulation led to a breakthrough and subsequent failure.

I had to completely unwind the rotor and rewind it with the same diameter enameled wire (the damage was on one of the innermost windings). Here we have a 220V mains, so the motor might be slightly different from the more common 110V US units.

Blender is pretty old, Vitamix wants a serious chunk of $$$ for a replacement motor. Admittedly I had to spend quite a bit of my free time to get this fixed, but it really only cost me $40 in raw materials.

Breakdown of the vitamix blender. Should've taken more photos.

What a new motor will look like, inside is essentially an open frame universal motor.

The rotor out of the motor and me unwinding motor. I had to remove the center insulation pieces all around and document how each winding was interconnected.

Another shot of the old windings.

I drew a little diagram to sort out what goes where. The motor had 22 commutator segments and the same number of slots for the wires to wind around. Each winding was 22 turns of enameled wire.

The motor partially wound, I elected to solder every end onto the commutator for a more reliable electrical connection.

Cleaning the completed motor to prepare for application of red enamel.

Red enamel applied on one side.

The original bearings on the rotor were made by NMB, 608SS. SKF does the 608RS that's also a rubber sealed bearing.

After the enamel has cured, this is what the rotor looks like.

Replacement bearings side by side with the existing ones.

I had to grind and cut off parts of the bearing to remove it piece by piece to get them in. There was insufficient clearance to pull them off.

Bearing inner race still left on shaft, for this challenging location I ground 2 flats on the inner race and used a vice to apply pressure until the inner race cracked and separated from the shaft. Usually this works quite well because the races are super hard.

Replacement bearing now on.

Motor assembled together, sans the 2 brushes.

Motor assembled into the blender.

The ass end of the motor/blender. A plastic impeller that moves air for cooling the motor goes here.

The blender finally together. It was tested out and it really kills ice cubes (we tried blending a bunch of ice).

On a side note. Happy new year everybody 2015 went by really fast for me, here’s to 2016.

Update: 17th April 2016

The Mechanic has kindly went ahead and did up a professional looking diagram of how the motor is wound up. I hope the motors he has get fixed.

Note that the commutator is not shown in the top down view, only the windings are.

Philips 40PFL5507H TV firmware restore

2015-05-17T11:43:00.001+08:00

Came back home one day to an hourglass on the display of my TV, instead of the usual power up sequence.

It just sat there for a couple of seconds before going to a blank screen. Reading online I found that it could be due to a corrupted firmware.

From the Philips website I downloaded a copy of the latest firmware and put it on a USB thumb-drive.

However I was unable to get it to start the firmware installation process, regardless of the different methods that the help file included within the firmware download suggested.

I then looked around more and found a copy of the service manual for my TV here.

https://www.scribd.com/doc/178909518/40PFL5507H-12-pdf#download

In it, there was a method to invoke an alternate or backup software/firmware function, to be used in the event the default upgrade application does not start (sounds like me).

1. Disconnect TV from power.

2. Hold the DOWN cursor while reconnecting TV to mains.

3. Backup software application should start.

Following these steps I managed to restore the firmware on my TV (I had to go through channel setup as well, since those were lost)

With that done, I proceeded to enjoy some Discovery Channel.

Yashica GT Pad of death + Rangefinder cleaning + Light seals

2015-02-24T16:49:00.001+08:00

Picked up a Yashica GT for cheap (under USD$15) locally which was known to have the POD (pad of death) issue, basically a small foam piece inside goes crumbly and then the shutter will start going crazy.

First steps are to disassemble the camera until you can see where the pad is.

Here I’ve removed the advance lever.

I planned to do this over the course of a few days, so bagging and labeling the parts was important, putting it all together and then finding out you have some stuff still on the bench is not cool (been there done that).

ASA dial comes off next.

Below that is a little washer which is basically what keeps the stationary part of the dial in place.

Now we have the film rewind knob

I wrapped tape around a screwdriver for me to use as a leer against the knob.

There’s a small washer right under there.

Below that there’s yet another washer that I guess keeps light and dust out of the innards.

After removing 3 screws around the top cover,gently pop it off, there’s a wire still in there for the flash, so be careful.

I chose to de-solder this wire so I wouldn’t have to be mindful of it while working on the camera.

Residing within the top cover is the battery test button, I took it out before moving the top cover too much (prevents it from getting lost).

Here we can see the problem, right there (just above CA in Yashica) is the deteriorated pad.

To get at it, you’d have to separate the lower mechanism from the upper. I did this by temporarily re-installing the advance lever, advancing and then using an allen key depress the lower mechanism.

With that out of the way now, we can get at the pad, there are other methods that involve disassembling more of the camera so you get better access, however that involves removing part of the leatherette on the front of the camera, I didn’t want to risk damaging that so I chose to do it ‘surgically’.

Here I’ve straightened out a bobby pin (from SWMBO) and put a small bend on the end to scrape out the remains, it helps if you can hold the camera upside down so the stuff falls out. Initially I wanted to use some of that black foam as the replacement material, but it was too soft.

For a far sturdier material I opted to use a small piece of eraser, the critical dimensions are 5mm x 4mm x 2mm.

Using the bent bobby pin and working upside down I leveraged the replacement piece into place.

Here it is back into place.

My camera had a sorta haze all over the rangefinder window, cleaning the glass and lenses that were reachable still didn’t quite cut it, contrast was really low on the RF patch, so I bit the bullet and attempted to clean the rangefinder innards.

This copper plate is all that exists between the the innards and us. Using a utility knife I slowly leveraged it out. A few drops of cement are all that holds it on, it is quite thin and feels fragile though.

Initially I cleaned everything in here with a Q-tip soaked in lens cleaner except for the beam splitting element (the gold coated piece), as I’ve heard that the coating can be extremely fragile, however the RF image was still not very clear because of the build up on there, so I went ahead and cleaned it anyways using no pressure at all (a damp Q-tip and then just dragged it over) the coating didn’t appear to be damaged, be very careful though, I’m not sure how much it takes to get it off.

I also replaced the light seals on my camera, they were starting to fall out in some places.

Didn’t take too many pictures of this process but it’s really simple. I taped up the rear with a piece of paper and some tape to prevent anything from getting into the rear lens element area. Then using alcohol and a plastic pick (it was a dental pick thingy) I removed as much of the old seals as possible.

New light seals were cut out and re-glued back into place.

I’ve so far shot a roll of Ilford HP5+ through this camera and the results are really good, the metering is easy to use (either the shutter speed is too slow or fast, but you don’t know by how much) and the lens is fantastically sharp. Focus is spot on, on my camera at least, a pretty good deal for what I paid for this.

Auzentech X Meridian 7.1 1G. Sudden loss of audio Part II

2014-12-30T00:26:00.001+08:00

Just a quick follow up, it’s been a few days since I’ve removed the output muting transistors and my sound card has been working great. I’m not planning to replace the transistors but I dug around for some information as to what they are.

The original removed parts are in a SOT-23 package, marked MAX on top with 2 small numbers (33) going the other way, which I later found out to be the lot nunmber.

Searching on

http://www.s-manuals.com/smd

led me to this part number KTD1304 and datasheet

http://pdf.datasheetcatalog.com/datasheet/kec/KTD1304.pdf

It’s manufactured by KEC in Korea, which sounds about right given Auzentech is a Korean company, I hoever can’t find this part stocked on the usual suspects (Digikey/RS Components/Element 14).

I did find some sellers listing it on Ebay though, so that might be an alternative if I ever want to get them changed out.

Electroschematics has a great article as well as an excel spreadsheet of some of the other available specialized transistors suitable for audio muting.

http://www.electroschematics.com/9660/muting-transistor-attenuator-circuits-2sc2878/

Auzentech X Meridian 7.1 1G. Sudden loss of audio

2014-12-27T23:50:00.001+08:00

Had an Auzentech X Meridian 7.1 as my main PC’s sound card for quite awhile (since like 2007 I believe, when they first came out), it has been working flawlessly (even after I moved from WinXP to Vista and then now Windows 7).
One day I was listening to music and the sound suddenly just dropped out on the front left and front right channels(I only use the front channels of the card), just before it went there was a very slight pop, a very subtle one.
Initially I was thinking maybe it’d be a driver issue, Auzentech has since folded, so the only real copy I got was from http://www.touslesdrivers.com/index.php?v_page=23&v_code=32167
Reinstalling the driver didn’t fix my problem though, a few hours later and the issue was back, audio will just suddenly drop out without warning.

I pulled the card and did some quick visual inspection. Didn’t actually see anything really wrong. So I cleaned it up and re-installed the card, puzzled.
The next time the audio went, I could actually just about hear some audio still going, turning up the volume in Windows confirmed there was actually some audio coming through, which told me the DACs and main IC on the sound card was probably working right, but something was causing the audio level to drop drastically.

Initially I suspected maybe the +/- supplies to the output opamps were somehow cutting out. +/- supplies are derived from the PCI +/-12V going through a 7808 and 7908 regulator.

The sound card is actually flipped over when installed in my PC, so there was no real way I could measure the outputs when the card was operating, so I opted to put in 2 wires to let me monitor the regulator outputs, I was especially interested in what was happening when the audio disappeared.

Adding these set of wires somehow made the sound card actually work for about 1/2 a day before crapping out. LOL. However the volatage stayed stable even when the problem occurred. So it’s something else.
Before I shutdown the PC to pull out the card, I ran my fingers over the entire area of the sound card and realized the output muting transistors for the Front Left and Front Right channels were getting extremely warm, I didn’t think they were supposed to get so burning hot (it was warm enough that I couldn’t put my finger on it for more than 2 secs).

I pulled the card and desoldered the monitoring wires, at the same time I tested the muting transistors with my multimeter, for some reason they measured okay on the diode range, I guess the fault is intermittent somehow.
After de-soldering the muting transistors I’m happy to report that the card is working okay. I’ll update if anything changes.
The muting transistors actually shunt the output to ground when the processor demands output muting (especially during mode changes). I can now hear a pop every time I change the output (changing it from say 96kHz to 44.1kHz), I don’t change that very often so I guess I’ll leave the muting transistors out. The original transistors are marked MAX33 (SOT23 package) which I have no idea refer to which actual part, I guess finding a suitable mute capable transistor and substituting that in shouldn’t be too big of a problem.

NAD 7125 Receiver Repair

2014-12-25T20:24:00.001+08:00

Been awhile since I last posted, pretty busy with real life recently. Don’t worry though, I will keep updating my blog from time to time.
Got this about a year back during a friend’s housewarming to fix, and yeah I basically forgot all about it until recently when I was clearing out my storage rack.

Initial power up, the amp section seems to be okay (at least it doesn’t have any serious offset that might blow up a speaker if I connected one up. Aux and Phono inputs seem to be okay as well, so I hooked up a test speaker.
The FM/AM tuner sections were stuck at 0.00 on the display and would only move by 1 step (50Khz on FM) and go back to 0.00 when I released the UP/DOWN buttons. So I disassembled the receiver to try and fix that.

I managed to get a service manual off the internet, it had the complete schematics plus tuner alignment instructions. Google “NAD 7125 service manual”.

Initially I thought maybe the main IC controlling the tuner section was wonky somehow, so I set out to measure some voltages.

Voltage checks on the ‘G’ ribbon (that carries power to the tuner section all checked out good.
Voltage check on IC6 (TC9137P) was ok as well.
Wires to the LED display were also verified to be good.
Output of a 5V regulator (78M05) IC7 was also good.
I managed to get the tuner to somehow work when I cut 2 cable ties holding the LED wires together as well as remove the LED display bezel to see if there was anything wrong there.
I thought somehow maybe the paper washers holding the LED display bezel had become conductive and impeded correct operation, but I was really not confident I had fixed the problem.
I went ahead and programmed a few of my favorite radio stations into the channel buttons and powered it up every day to see if the issue would recur.
The fault re-appeared 3 days later, but the difference was this time it was not 0.00, but rather the station that I had programmed into channel 1.
This of course makes sense now, the tuner hadn’t been powered on for a pretty long time and had lost all it’s internal memory, so the stored frequency in every channel was 0.00Mhz and it was trying to switch itself to 1 all the time even when I was tuning it manually with the rocker. The pushbutton switch on channel 1 was basically conducting sufficiently to cause the main tuner IC to sense it as permanently depressed.
I sprayed a little Electron 22 into the switch and exercised it a couple of times and tuner function was restored.

At this time I went ahead and tweaked the amplifier’s center voltages and idle current to 0.00V +/-30mV and 30mA. Before tweaking it was running a very low idle current (2mA), not sure if it drifted or someone was inside here previously with a ‘golden screwdriver’.

There are 2 potentiometers per channel on the amp that control the offset (center) voltage and the idle current. To do this you’d have to 1st zero out the output as best as you can (without any signal input of course, I do it by shorting out the AUX jacks, turning volume down to minimum and switching the input to AUX).

The emitter resistors are what you’d need to measure to determine the idle current.
V=IR
I = 30mA and R = 0.1Ohms
V=(0.03)x(0.1)
V=3mV
So to get a 30mA idle current you’d need to adjust the pot till you get 3mV across 1 leg, each emitter resistor in this case is actually a combination of 2 in one package, with the center lead common (to the output). Check both sides after you’ve adjusted to make sure they are close.
After adjusting it in, leave the set for awhile and come back to re-confirm it’s still stable on both sides of the emitter resistor just in case it drifts.
I also spent some time dusting the interior, in fact the pictures taken above are after I’ve removed most of the dust.

After listening to the receiver for abit I noticed yet another issue, the Stereo LED only lighted up very rarely and attaching a longer antenna plus shifting the unit outdoors (I was testing it in a semi electrically noisy environment, near PCs and stuff) didn’t help.
Measuring the MPX VCO output with my DMM that had a frequency counter option showed it running at 78kHz, which was out of limits, should be smack on 76Khz (+/- 10Hz).

I don’t own a RF generator to test and align the tuner in accordance to the steps outlined in the service manual. So I used an alternative method to get it in.
I marked the VCO potentiometer in 3 places (it’s one of the those crappy wobbly ones that can shift around as you’re turning it, so it’s gonna be hard to get it exactly spot on if you only marked it in one spot) to enable me to return it to the original point if this adjustment didn’t help.
Then I tuned to a strong station mid-band (in this case I used 98.70FM).
Pot was then turned fully CCW (counter clockwise) and slowly turned CW to just where Stereo LED indicator came on, this is position A.
Pot was then turned fully CW and slowly turned CCW to just where the Stereo LED lit, position B is here.

Finally I set the pot to between position A and B, measuring the VCO at this point yielded a stable 76Khz.

Listening with a pair of headphones confirmed the tuner was in stereo (there was audio separation), switching to mono turns the Stereo LED off and results in no separation.

I then tested other stations across the band (88-108Mhz) and found that they went into stereo reliably.

After I was satisfied with the results I replaced the cover and touched up some paintwork on the front panel that was scratched. I still need to go out and get some replacement knobs though, but at this point I’m really happy with the results.

On a lighter note. Merry Xmas everyone!

Fixing a Viewsonic Viewpad 7 with flashing red charging indicator

2012-12-03T18:26:00.001+08:00

Had one of these land in my lap from my cousin, the unit would not power on. Hooking the adapter up to the unit will just cause the power LED next to the switch to just keep flashing red and no button inputs result in anything.
Tearing apart the unit was pretty simple. A stiff plastic card was used to carefully separate the back from the tablet. You wanna be careful doing this as the plastic is rather thin in some spots.

Viewsonic has helpfully left some voltage probe points right next to the battery connector for easy troubleshooting. In my case the battery read 2.5V, way under the nominal Lithium Ion/Polymer voltage of 3.7V. I suspect the unit might have been left to drain for a long time.
Hooking the charger/adapter to the tablet overnight didn’t charge the battery one bit, so I went hunting for a suitable replacement battery.

A shot of the new battery that I found locally (top's the old deadish battery). The original battery was 3250mAH. The new replacement was physically smaller in terms of width and length, but slightly thicker. I confirmed that it’ll fit in before purchasing it. The only drawback was that it had a capacity of 3000mAH, so I expect to have slightly less battery life compared to before. Oh well. The replacement battery costed me around USD$25. I’m sure with enough hunting around I might be able to find a better replacement, but for this price I think it can’t be beat.
The protection circuitry that resides on top of the old battery needed to be swapped over to the new cell, so I proceeded to cut the insulating tape and pull that off.

The new cell came with some circuitry as well, but since it won’t work with the Viewsonic tablet, it’ll have to go.

A picture of the protection PCB that’s going to be transplanted.

At this stage I had used a pair of pliers to carefully undo the battery tabs that were spot welded onto 2 metal plates soldered to the PCB. Then used a high power (about 60W) iron to remove the plates since I was going to solder the tabs to the PCB. I believe the plates are just there to let them spot weld the battery tabs onto the PCB.

Here’s a picture with one of the battery tabs soldered to the PCB. The tabs on the new cell are in a different position from the old, so I had to solder one end and jumper the other to the right pad on the PCB.

There’s the positive end that’s jumpered. I used 2 thin wires to try and increase the current carrying capability without compromising on the battery’s thickness too much.

Battery’s finally all done up and taped together. I just used some packing tape.

Installed and lying sideways inside the provisioned battery space. At this point even though the cell measured 3.8V, I didn’t measure the same voltage on the tablet’s test point. I tried plugging in the adapter and powering on the unit, lo and behold the screen came up and the test points measured 3.8V. I‘m guessing the electronics on the protection PCB can actually stop current from reaching the tablet (shutoff the battery totally) to prevent draining the battery too deep when it’s flat.

After confirming it works. I applied a little Dow Corning 3145 to the underside of the battery to secure it to the tablet. Wouldn’t want it shaking around inside.

Not forgetting the SIM+MicroSD protective cover, I re-assembled the tablet.

There it is, looks just like before.

Uhhh, not too sure what kinda wallpaper that is, but it works.

And it charges…

Broken Logitech G25 Part II

2012-07-25T17:53:00.001+08:00

Finally got the parts in the mail, I left the G25 disassembled the whole week and it was lying on my room floor, starting to get a little obnoxious. Here’s a shot of the broken FET.

I ordered 2x both N and P channel dual FETs, although only the IRF7103PBF was actually shorted on mine.

Proceeded to solder the replacement in.

I just held it on top of the pads and tacked on corner on. Then adjusted the whole IC until everything lined up and completed soldering it on. Not the cleanest job, because some of the pads on the board have no mask, so it looks like a couple of pins are shorting, but electrically it’s alright.

I then proceeded to re-assemble the motor and linear gear together.

I left the wheel installation out till I could see if the wheel would fire up and calibrate. During re-assembly I just put the linear rack gear somewhere in the middle and ta-da, it worked during power up and could calibrate properly.

There was a little bit of arcing and smell from the cleaned up motor though, I suspect the brushes haven’t bedded in properly yet. I then plugged and unplugged the wheel a couple of times to get it to cycle the calibration process more and that fixed itself. There was also some cogging present initially, that’s also fixed.

Proceeded to finally play some GT5.

Broken Logitech G25 Part I

2012-07-17T22:20:00.001+08:00

Wanted to play a little GT5 over the previous weekend. Hooked everything up and turned the PS3 on.

The G25 normally does a little calibration routine at the start, but this time it did a little quarter turn and sat there motionless. Power LED on the shifter just kept blinking, I thought WTH and decided to try rebooting the PS3. Nope, this time it wouldn’t even move and just kept blinking.

Plugged it into my PC, and everything works, except the wheel. I’m guessing without the calibration routing, the wheel axis will not work.

Measured the power coming out of the adapter and it was a stable 24V, as per the spec on it’s label.

Next I tore into the wheel itself to do a little poking around.

The 1st thing I suspected was the motor driving circuitry. Disconnecting both motors and probing around the vicinity confirmed that I was right, one of the dual MOSFETs in the IRF7103 was a dead short.

Proceeded to remove the FET and see if it’s really dead, or something else on the board had died.

Yes it was dead. Removed and re-probing with my trusty DMM confirmed that. I put both the FETs on order (IRF7342 and IRF7103) thru RS-Components (actually only the IRF7103 had fried, and it was a single FET in the dual FET package).

I then decided to find out what exactly killed the FETs, wouldn’t want my replacement to go up in smoke the second I powered it on, why did the wheel turn 1/4 way before coming to a stop?

Removed a couple of screws and disconnected a bunch of stuff to get the gearbox and motors out where they could be comfortably moved around. I then decided to probe the resistance of both motors.

Here you can see that one motor has an encoder (where I guess the wheel actually gets it’s axis signal).

A pic of the reading I got from the motor with the encoder on the back. This is the min resistance (I spun the motor slowly by hand and used the DMM’s min function).

One of the ‘other side’

I pulled the motor leads out of it’s connector and tried using the power adapter itself to power the motor with the encoder. Bad idea, a whole bunch of smoke came out of the commutator area and the motor just jerked a little and sat there pretty, whilst more smoke poured out. I quickly disconnected the wires.

Can’t really see the commutator in this pic, I then disassembled the whole motor so I could see what was going on inside, initially I suspected that maybe a winding was somehow shorted or the brushes were somehow shorting together.

Here’s what I saw after prying the back out. Look at the gaps in between the comm segments. A mixture of oil,grease and carbon has built up inside and I’m guessing is the cause of all the problems I’m having.

I dug through my drawer and found a little pin that was small enough to fit into the gaps and used that to clean it out. Together with some contact cleaner.

This is the amount of crap that flowed out.

All that black stuff came from the commutator. After cleaning I measured the resistance again.

Not too bad I’d say, pretty close to the other motor. For that motor I just sprayed a little cleaner into the comm through the side gap and called it good.

Piecing the thing back together. I had gouged the end ‘tabs’ a little during the disassembly, and ended up just using a small punch to wack 4 tabs back on afterwards, seems to be tight enough to me.

I also noticed a little crack on the encoder wheel and used a little bit of CA glue to stick her back together. The wheel just slides onto the shaft and is held there with friction.

Look forward to Part II where I replace the fried MOSFET and try powering her up! I have the parts on order right now and am waiting for them to arrive.

Gigantic Hiberfil.sys in Windows 7

2012-07-08T17:28:00.001+08:00

You’re reading this coz you have a tiny (40GB) SSD like me for the OS drive and there’s a gigantic (mine was up to 12GB before I had it removed) hiberfil.sys file and you want it gone to free up some much needed space? Fear not, this post is for you.

As far as I can tell, hiberfil.sys let’s your PC Hibernate, Windows will use hiberfil.sys to store it’s current state, and since windows is managing it, you can’t delete the file. Until you do the below steps of course.

Open up an administrator mode command prompt, and put this in.

powercfg -h off

You should immediately notice the Hibernate option gone from the shutdown menu, as well as, TADA, a bunch of free space on your C: drive (the file hiberfil.sys should also be gone from the root directory).

Note: I forgot to take screen captures of the process, sp yes you’d have to put up with a wordy post. Sorry.

Cool Manga guide to SMT

2012-06-03T17:06:00.001+08:00

Found this while surfing the net the other day. I think its really cool and a good idea. Should help those getting started into SMT soldering. Best of all, it’s free.

http://www.siliconfarmers.com/smtmanga/

It kinda reminds me of this one.

http://nostarch.com/mg_electricity.htm

Quieting a whining inductor/SMPSU transformer.

2012-05-19T21:50:00.001+08:00

I recently got a little Li-Ion charger that’s based of a SMPSU. It had the nasty habit of whining during charging though (it’s loud and annoying).

I decided to tear it apart and see if I can pot it in some epoxy. Of course best results would be if I could put the whole thing is some sorta vacuum to get rid of any voids and air bubbles. I didn’t have that handy, so I used some slow setting epoxy that’s very fluid.

Here’s the charger disassembled. The topside

And here’s the bottom, I then desoldered the little switching transformer that’s making all the noise.

Here’s that pesky transformer

I then used a little masking tape to form a crude sorta mold, keeping all the epoxy from flowing all over the place. Here I have poured in the epoxy

Here the epoxy has cured and I’ve taken the tape off. Seems to have covered everything.

I then assembled everything and tested the charger out. Glad to say a lot of the whining has been removed. I now need to put my ear up next to the charger to hear a perceptible whine.

Hehehehe…

2012-04-30T22:48:00.001+08:00

I found these pictures on an old harddrive when I hooked it up today.

Enjoy