A short hit for the soldering: Lock carefully at the modules you intend to use. very often these have universal PCB’s carrying the chips. This means you have one PCB being used for different types and sizes of modules. Therefor the presence detect pins are not directly connected to GND but wires will leads to four solder pads (sometimes even marked with 1, 2, 3 and 4). If in doubt a multimeter will show up the responsible pads. I’m pretty sure that in the Simm picture above these pads are on the very right side of the front view of the Simm module. Look closely, there are 8 square pads, four of them connected to GND and the others to the PD-connectors of the module. It is very reasonable to use these!

So, instead of trying to solder on the tightly packed connector pins you could change the configuration with these pads. This might involve removing some pads already shorted, shorting other pads not yet connected and maybe un-shorting pads that are default-shorted (by a copper strip on the PCB, not by soldering). To unshort take a small, sharp knife and afterwards test with the multimeter.

I could possibly give some more detailed or additional information:

The table above is maybe not completely correct or a bit outdated. Compare here:

http://ps-2.kev009.com/eprmhtml/eprma/h871.htm

and here (German only)

http://www.elektronik-kompendium.de/sites
/com/0405171.htm

You will find similar tables elsewhere on the net.

So this explains why putting a “huge” 32MB Simm into an old printer will show up only a small memory size: Due to the lack of presence detect pins older bit combinations later have been reused for larger modules: 1, 16 and 64 MB Modules share the same bit combination, same is valid for 2, 32 and 128 MB as well as 4 and 256 MB. Very old printers (or computers) don’t know about this fact and thus 16MB will show up as 1MB only. This limits the amount of maximum memory you can use with this systems.

Then some points concerning the old LJ4 (non plus model):

This printer falls into above category, 32MB is the maximum upgradable memory amount, using 4 x 8MB FPM’s. This printer does not accept EDO (didn’t exist yet then). It does however *require* parity Simms (later printer do not). It can accept both double sided Simms with 8 or 2 ram chips on each side (the parity rams left aside, in sum these do result in 3, 12 or another number of chips on each module side). And it does accept FPM’s with 70ns or slower access time *only*, all others will be rejected. Nevertheless you can down-pimp faster modules to cooperate with this printer. I was able to get 60ns modules running. Simply resolder these modules to pretend to be 70ns modules and the printer will accept them without a hasle. Generally speaking, faster modules will always be able to run in a system requiering only slower modules. So you will do no harm to any component involved. This is simply a problem of an outdated printer firmware. At the time the LJ4 was build there were no 60ns FPM’s and the bit combinations later on used for these were undefined. so HP made the firmware recognize these as illegal instead of blindly assuming a certain speed and size. So, just make the printer think it were 70ns modules and everyone’s happy!

The original online purchase was supplied without the speed detection being set and Arch Memory immediately sent a replacement without requiring any return from NZ. That’s great service. With nothing to lose, I decided to give this a go and ended up with two working cards! I used resistor leads and a jump wire.

FYI – The 16MB ram lights up all the lights on the printer and it then appears to freeze, unlike the original 6MB which is ready almost immediately.

Like others, I thought S%#@ and immediately turned it off. I reseated the card and also tried other slots and rechecked the detection modifications. Everything looked okay, but I still got the apparent lockup.

However, further Web research found others had encountered this and reacted the same way. Turns out the printer was only checking the Ram and settles into a single ready light after 35 seconds (45 seconds with the two extra cards).

The second gotcha – The replacement card (which had its speed and presence detection already set), did insist that it be seated in slot 1 before the printer would even fire up at all – so you may have to play around a bit.

Thanks

Thanks for taking the time to write and let us know that this trick worked for your LaserJet 4M Plus. You are welcome and happy printing!

-Dennis