HP-65 goes on hold after reading a card

[teenix]

(11-15-2020 11:37 AM)albertofenini Wrote:  Hi Tony
this is what we tested :

Storage Register : these all works well
Yesterday it was me using them wrongly
You can store in any of the 1 to 9 registers, you can recall the values, and you can do storage register arithmetic as well

Writing a program : we followed the example on the quick reference guide,
LBL E ENTER ENTER x x RTN, and it works, we even wrote it on a card,
turned off the unit, read it from the card and it worked, it was also read from
other units with no problems, I would say that the card reader works fine ...

Standard Pac programs : some programs like Day of the Week, Temp Conversion, Weight conversion are read with no problem and run, most like the Diagnostic don't
This behavior is consistent also using other Standard Pacs

Then, we have put into this assembly one known working hybrid board and everything worked perfectly, no problems at all
I would say the card reader and the led/keys boards are ok.

On the opposite, we have put this hybrid board in another unit and all the wrong behaviors were exactly repeated

I would say that the problem is within the logic board at this point ...

Could it be a ROM/RAM problem or one of the chips inside the Hybrid is failing ?
We have a set of the ROMs, would you suggest to try to replace them ?
All, one in particular ?

Thanks for help !!!

Because the fault shifts with the CPU card, the only thing I can think of is that the 600 bit program storage unit or card reader control circuit (CRC) inside the hybrid may have some faults.

If this is the case, then it can only be determined by changing the hybrid chip module, or having a close look at the PCB tracks and pins associated with the card reader control signals.

I don't think it is a ROM/RAM problem because unlike the 67, the card read/write is a separate system, but you never know.

I'm guessing here, but from what I understand, the HP-65 is a bit sensitive to timing problems, (say) different card speeds compared to the CPU clock speeds or vice versa. I don't know if this is the issue, but reading long programs from the cards might have errors because of a timing imbalance, whereas short programs might run ok.

This might be determined by writing (say) a 30 step program to a card and reading it back. If it works, try a 50 step, 70 step, then a 90 step and finally a 100 step program. If things begin to fail with longer programs then it might be a timing issue, but as I say, just guessing.

You can check the card by monitoring the head switch and the RA/RB data. The data should clearly appear inside the points where the switch operates.


cheers

Tony