(HP-41) strange behaviour, needs repair

[Hiwi]

Hi,
i recently bought a very nice looking HP-41C serial 2130A.. from ebay. The seller said, that it is fully working.
The calculator looks like new, never been serviced, but does not work correctly:

You can do normal calculations, SIN, COS ... I think that is what the seller has tested. But I
can't enter any programs.

Switching to PGM mode shows a NONEEXISTENT message. SIZE 000 ,0049 0063 is working and i can access and store data in the registers. But no program.

When USER mode is on, i can make calculations but not SIN,COS,TAN in this case ALPHA turns on, and i can see the KEYCODES! Switching OFF returns to nomal display.

GTO... does not work either, i see forever 'ACKING _ ' instead of PACKING. SAME with function XEQ PACK.

Is the CPU faulty or ROM, can I do some other checks, PSU?

RAM should be ok, since I can store data in different SIZE options and make KEY assignments.

In case it is not repairable, has anyone a spare mainboard for sale?

Ralf

[Hiwi]

Hi,
someone gave me the hint to clone the sevice rom into the nov64, and this shows the ERROR 3 ROM 0 BAD.

I am once more very enthused what a great engineer performance this little HP41 was given to.

It was made to last forever. :-)

Ralf

[ThomasF]

Hi Ralf,

(02-27-2023 09:43 AM)Hiwi Wrote:  In case it is not repairable, has anyone a spare mainboard for sale?

There is a store in Spain which normally sells 41 motherboards (but out of stock right now) ...
Full-nut motherboards

Cheers,
Thomas

[Guenter Schink]

(02-27-2023 09:43 AM)Hiwi Wrote:  In case it is not repairable, has anyone a spare mainboard for sale?

have a look at your private message

Günter

[Hiwi]

Hi all,
the problem is solved. i got replacement parts from a member of this forum. Thanks again.
I changed the ROM0 chip from the working board to be sure that it was the only fault and now it works again.
Ralf