HP25-C



#3

Last year ( July 16th ) mr. David Smith give the solution for my HP25-C. Broken C-MOS type 7626 HP indication( 1820-1630 ).

Where can I obtain the C-MOS ?? Are there replacements ?
For me it is a challenge to repair the HP25-C myself.
Louis.


#4

The only source of the chips is another machine. You can find compatible chips in the HP25C or HP29C. The 25C had two types... a two RAM chip version or a single RAM (double capacity) chip version. Since the 29C has much more memory than the 25C, it used two of the double capacity chips.

Now the tricky part... there is a slight difference in using the two types of chips. There is a 100K pull-up resistor on one of the RAM chip pins (sorry, I don't remember which version uses the resistor and which does not). If you change RAM chip types in your machine you will need to either add or remove the resistor.


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