Hp-25 needs service


Recently, I bought a defect HP-25. One of its problems is corrosion due to battery leakage. There was already some work done on the keyboard PCB which I had to complete. Now it it fully working again, i.e., all keys contacts are open and work and damaged traces are bridged. I'm fairly sure that thing is ok now. Still have to reconnect the faceplate but that appears to be a minor problem. At least, I have an idea how to do it.

There is some residue from the leakage on the main PCB and on the comnnectors but thus far all traces seem to be ok. I put both PCBs together and measured resistance of all contacts of both connectors. All is well here.

Now soldered wires to the battery contacs and connect them with the battery pack containing two AAs. Polarity is ok.

Finally, fired that thing up. At first, there was nothing, then slowly some segments of the display lit up in the middlest elements. Something like an incomlete 77. Switched it off and on again, same effect. Also, it is not as bright as expected.

Some keys have an effect on the display, most notably the decimal dot.

My question: Is this behaviour a sign of a bad chip? I know that problem with fried internals so I'm a bit scared now.

Thank you very much,



Has really no one had a Woodstock that behaved like that?

I tried to search this forum for 'woodstock' and 'act' but only found something in the articles section. Is it impossible to search in older posts? I'm sure I've read something about it but don't remember where and when that was...


Is it impossible to search in older posts?

Hello Thomas,

I usually prefer to use Google whent searching for older posts. For instance, the search key site:hpmuseum.org Woodstock + ACT returns 81 results:


I hope you find something that may help you there.




Yes, thanks Gerson! I missed the museum keyword so I was a bit lost in woodstock acts ;-)


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