Pr Error HP-34C


After spending some time and rummaging three HP-37E's I finally got my HP-34C working (somewhat). The unit passes the self-test, RAM is functioning and program storage works fine, though I had to implement a make-shift battery clip since the best battery terminal I had still had a missing terminal due to corrosion.

What's happening now though is that every time I shut the unit off and wait more than a minute generally, the unit will power back on with the PR Error displayed. Is this a failed cap?

Thanks in advance.


I use a 34C with normal AA NiMH cells with the circuit completed on the right side of the compartment with a thin strip of aluminum foil. I found the old battery clip was too snug with regular AA cells and this works fine. It also makes it easy for me to pop out the cells and charge them in an NiMH quick charger. The Spice power adapter was intended for NiCads and will work with the NiMHs but takes forever to charge fully.

I was erasing my memory occasionally when removing batteries and it took time for me to realize that if I wasn't careful the foil strip would zip across the compartment and touch the contacts and discharge memory that way.

So I am wondering if your homemade clip could be the issue? Is the circuit being closed someplace it shouldn't be?

If your clip indeed is not the problem and the batteries are fine then I fear it could be the electronic innards and I hope someone here can guide you!



Thanks for the response. The battery I'm using is the standard HP rechargable for the spice units, in good condition. The make shift terminal is the - clip on the ribbon terminal.

I did make sure that the clip isn't shorting out anything and yet I still get the error. Again, this error is produced if the unit is left off for > 30sec


OK, I think I may know why the error is being generated. Question is the PSU board for the 37E the same as the 34C? for this is the replacement I used.


No. The "C" models use a different PSU to provide standby
power to one of the three 8-pin chips (the one closest to
the display).

If you have the wrong PSU, or hae the 8-pin chips in the wrong
order, you don't get continuous memory.

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