HP-41C service module question

[Jurgen Keller]

Today I've used the ET-11966 service module to diagnose an HP-41C which doesn't work properly (whenever turned on it shows 'MEMORY LOST' and does not react to any key press). While browsing through the service manual I stumbled across the "ET-11967 Flag-Wired Memory Module". Apparently it's used to diagnose the I/O ports. Does anybody own such a module, or has any information about it? I don't know the exact meaning of the term "flag-wired" in German, however, my guess is that the lines are wired in a special way to each other, allowing for diagnosis. If so it might be easy to rebuild it (e.g., out of an unused memory module).

In an old thread (41C Service ROM?) Philip Reagan mentions that, besides the service module, he owns an unlabeled module that might be such a flag-wired memory module.

BTW, the result of my testing was that the D/S test reports a bad data storage IC [D/S 3, BAD].

[HP-Collection]

Which version of the Service ROM do you use?
1A, 1C, 1D, 2A or 2B ?

Matthias

[Jurgen Keller]

I use SM-1C aka ET-11966, the one described in the HP-41C Service Manual. There I also found the reference to ET-11967, see table 4-1. It's required to run the I/O Port test routine, see table 4-2, step 12. As in my opinion this is a very useful test, that's why I'm looking for information about this additional module.

I just checked the HP-41C/CV/CX Service Manual, and interestingly it does not mention this flag-wired module anymore. Instead it references an ET-11945 Port Extender for I/O port testing, see table 4-1 "Recommended Tools" and table 4-2, step 13 (I/O Port Test). Of course it would also be interesting to know more about this "beast".

[Ángel Martin]

It looks like there are many more unanswered questions than available answers... I only knew of the existence of the following diagnostics ROMS:

1. ET-11966, for the 41C/CV - includes Card Reader tests
2. Service Module 0004160937 - for the CV/CX . No Card Reader tests.
3. ET-14048 HP-IL Diagnostics ROM
4. ET-11968 82143A Printer Service ROM

Never heard of the flag-wired or the "Port Extender I/O" counterpart though.
Either a red herring or a real myth? We'll probably never know...

[Jurgen Keller]

(10-20-2014 01:26 PM)Ángel Martin Wrote:  Never heard of the flag-wired or the "Port Extender I/O" counterpart though.

At least they are mentioned in the service manuals so I believe they existed once. However, probably all of them have entered the happy hunting ground.

[Diego Diaz]

Hi Jurgen, all,

I found the references about the ET-11967 wired memory module some time ago, and according to the (few) details from the Service Manual, my best guess it that it's just a double memory module internally wired.

This was required to have an HP-41C at full memory (320 reg.) while having the SM plugged. Obviously it becomes useless once the Quad Mem module was available.

I also built a replica of said ET-11697 and perform the tests in the manual to confirm it shows the expected results. It does :-)

Regarding the first problem you mentioned: MEMORY LOST on power on with SM plugged. It seems to be related to I/O port connector problem (assumed SM is OK) or CPU board.

Any other hints? Does the HP-41 under test show other symptoms when in operation?

Keep us posted.

All the best from Canary Islands.

Diego.

[Jurgen Keller]

(10-22-2014 01:42 PM)Diego Diaz Wrote:  I also built a replica of said ET-11697 and perform the tests in the manual to confirm it shows the expected results. It does :-)

That's very interesting news, Diego! It would be great if you could publish the information how to rebuild it :-)

(10-22-2014 01:42 PM)Diego Diaz Wrote:  Regarding the first problem you mentioned: MEMORY LOST on power on with SM plugged. It seems to be related to I/O port connector problem (assumed SM is OK) or CPU board.

Any other hints? Does the HP-41 under test show other symptoms when in operation?

The MEMORY LOST also shows up without the service module plugged in, and the calculator does not respond to any key press. So I guess the diagnosis of the service module that D/S 3 IC is bad might be the correct guess. I have to cannibalize another HP-41 to test that, and have to postpone that a bit.

[Diego Diaz]

Hi,

I just wired a second 82106A PCB inside a standard memory module, but without B3 & B4 lines.

So when the module is plugged into port 2, the 'original module' takes its address from the port wiring; while the added PCB memory is allocated as if it was plugged into port 1; where the Service module is installed.

As you can see, no rocket science whatsoever... ;-)

All the best.

Diego.

[Bruce Larrabee]

I didn't see where anyone mentioned the schematic for the modification to the T-11945 port extender tool for I/O continuity testing on page 4-32.

[dmh]

Hi Diego,

I received a memory module that was open and I assume it doesn't work.

How can I make this module an I/O test module?

What type of glue do you recommend to seal it again?

Thanks

(10-23-2014 02:17 AM)Diego Diaz Wrote:  Hi,

I just wired a second 82106A PCB inside a standard memory module, but without B3 & B4 lines.

So when the module is plugged into port 2, the 'original module' takes its address from the port wiring; while the added PCB memory is allocated as if it was plugged into port 1; where the Service module is installed.

As you can see, no rocket science whatsoever... ;-)

All the best.

Diego.

[AndiGer]

The double memory module should be assembled as once described in the file http://www.hpmuseum.org/guest/klug/dblxmem.pdf isn't it?
Andi

[Diego Diaz]

Hi all,

The wiring I used for the ET-11967 replica was not exactly like the one used for the Double X-MEM.

I left the B3 & B4 lines without connection in the piggy-backed 82106A PCB, thus ensuring that it will always be allocated into port #1 regardless the physical port it is connected to.

Apart form this it's just a point-to-point wiring.

Hope this helps.

Diego.