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Is there a self test for HP41CV?



Yes there is, but unfortunately not built-in.
You need a service module,
OR an image of it and a RAM/EPROM box,
which is capable of setting the ROM start address to 4000h.

Happy New Year,


I have seen a display test on the PPC ROM if you have one. However, as the name says, it is only a display test. It is named "DT" on the ROM. It should work for any 41C series. Randy


So, the 41 doesn't came with a self test in rom.I think here in Brazil will be almost impossible to get on of these testing roms.


Peace, prosperity and happy new year for all

Marx Pio

to find a test ROM anyway! I have never seen one offered for sale. They certainly would be expensive too since they were never meant to be released outside HP repair centers.

Hi, Randy (and falks)

I've seen some posts mentioning the test ROM and recently this one from Pavel called my attention. I was not known that a separate RAM was needed to perform the test. After reading the post I realized that that would depend on what sort of tests were performed so an additional RAM would be needed to store intermidiate results, maybe, to be compared (does the FLAG name come from this?) to references already built inside the test ROM itself. Just wondering.

I have never seen the test ROM itself, and I would like to know how deep the tests go into calc's both O.S. and H.W., say, would the results give significant information for us who will try to repair the calculator? Or it would be valuable just to confirm the calculator's O.K. status?

As Randy mentions, the test ROM is somewhat hard to find. Is it important having it? I believe e-bay dealers should have one, so the 41's walking around there would be tested before going to final buyer...

Just wondering.



I don't know if any of these Test ROM's are available as modules,
but I know that there were at least two different ROM images for testing purposes.
AFAIK one for the C/CV (SERV1D), and one for the CX (SERVCX).
They are hard coded to address 4xxxh and act as 'takeover' ROM's.

Many years ago I had these, and they worked.



Hi, Raymond;

thanks answering the post. Now I'm somewhat curious: as the ROM is not a module, what is it? One single IC that is placed/soldered inside the calculator?

I cannot visualize it. What is it physicaly?


Hi Luiz,

I don't know they have ever been produced as modules,
but they are 'normal' 4K ROM images.
Maybe the HP-41 service manual gives a hint.

I used the images many years ago in my MBK ProfiSet,
a 32K RAM box from W&W.

I loaded them into the first RAM bank, then switched the base address to 4xxxh.
After turning the calc off and on again the service ROM had total control of the system.

There were some tests, of which I only recall the keyboard test.

It was somewhat difficult to get rid of it again,
since it's a takeover ROM;-)
I had to deactivate the ON interrupt vector of the image
to be able to delete it...



BTW: Obviously there existed another maybe interesting module for the HP-41:
The Demo ROM. I only have the keyboard overlay of it.
Black background, upper frame and letters in red, with the word DEMO on the frame, lower frame and letters in green, with the word CHRONO on the frame.
Row labelling from top to bottom:

the remaining key labels are just the numbers and the R/S label.

I got this kbd overlay from an HP dealer in the early eighties, but unfortunately not the ROM;-)

The HP41C servive manual (on the HPMUSEUM disks) mentions the "FLAG" module as being a modified RAM module used to test the flag inputs in the calculator I/O ports. I don't think it actually uses the RAM chip, but has a manual switch input that connects to the bus FLAG line.

the test rom for the hp-41 is a normal plug-in module. in germany it was called 'diagnose-modul'. i know of one CCD- member who got his hands on it. his favorite joke on computer fairs was showing the module to hp- representatives who consistently denied its existence and availability.

cheers, hans