HP-41CV Fullnut CPU-board wanted

[Martin Hepperle]

Hello,

recently I obtained an HP-41CV which when powered up shows only MEMOY-LOST and no keyboard interaction is possible. I was not able to bring it back to life. The keyboard and display seem to work properly and the connectors between the boards seem to be okay. Once or twice I was able to coax it into a CAT 1 display by removing/replacing the battery box.
Assuming that the CPU/RAM/ROM board has a fault I am looking for a replacement board. This machine needs a fullnut board (board with the two electrolytic capacitors in the edge cutout and the double-height stacked RAM chips) attached without nuts to the keyboard PCB.

Maybe someone has a CV with a damaged case, keyboard, display but a possible working mainboard sitting around?
Preferable in Europe to minimize shipping costs.

Alternatively I could transfrom this machine into a CL but I am still struggling with the (well justified) costs.

Martin

[Etienne Victoria]

Hello Martin,

You have PM.

Best

Etienne

[BobVA]

(02-04-2015 12:13 PM)Martin Hepperle Wrote:  ... and the connectors between the boards seem to be okay.

If it's got the elastomeric rubber "zebra strip" interconnect, I'd be suspicious of that. They can cause all kinds of strange issues.

If you can possibly swap it for another or, better yet, one of the flex circuit interconnects that might aid your trouble-shooting.

Bob

[Martin Hepperle]

(02-04-2015 10:25 PM)BobVA Wrote:  If it's got the elastomeric rubber "zebra strip" interconnect, I'd be suspicious of that. They can cause all kinds of strange issues.

If you can possibly swap it for another or, better yet, one of the flex circuit interconnects that might aid your trouble-shooting.

Bob

Bob,

indeed this CV has the usual interconnect with the twin gold plated zebra strips with a sort of silicone core and I examined it carefully. I did some resistance resp. voltage measurements and it seems to work properly, but of course these things are sensitive and I did not verify all connections. The interconnect to the battery compartement also looks fine - no corrosion etc. One of the top screw recesses had broken through and I fixed that. I also tweaked the white elastomeric block inside the battery-keyboard connect a little bit to get more pressure but this did not change anything.
My idea was to first try another board. If this produces the same error, I would probably go the hard route of soldering wires to the connector pads connecting the cpu board with the keyboard. But as this is irreversible, I would like to try a board swap first.

Martin

[BobVA]

Do let us know what you discover!

[Hans Brueggemann]

(02-05-2015 08:50 AM)Martin Hepperle Wrote:  indeed this CV has the usual interconnect with the twin gold plated zebra strips with a sort of silicone core and I examined it carefully.

martin, you may want to have a look here:
https://www.flickr.com/photos/75954327@N...9798561274

hans

[Martin Hepperle]

(02-10-2015 10:36 AM)Hans Brueggemann Wrote:  

(02-05-2015 08:50 AM)Martin Hepperle Wrote:  indeed this CV has the usual interconnect with the twin gold plated zebra strips with a sort of silicone core and I examined it carefully.

martin, you may want to have a look here:
https://www.flickr.com/photos/75954327@N...9798561274

hans

Hans,

thank you for this idea - I have checked mouser.de and saw that they only have 7 of these connectors in stock. Probably a sort of end-of-life product.
They have a replacement (538-78545-0010) which is thinner. As these are cheap I have ordered a bunch of them to see whether they can be used. If this does not work I will connect the boards with wires.

Martin