HP-65 1333A04841 restoration it doesn't work anymore ...

[teenix]

If moisture got into the hybrid then the vinegar solution may have ended up on the exposed chip surfaces but I don't know what this will do to them. Hopefully this did not occur.

Another thing that might happen is that if the inter-board connections (vias) were corroded and the vinegar wash has cleaned that off, they might not make proper connections. As it is a multi-layer board the inner layers may have broken or increased resistance connections also. Hard to trace.

There is an initialization circuit inside the hybrid that resets the calculator chips at power on (Init line - pin 36). If this is faulty it may start up erratically. I imagine it stays low for a short time at switch on then goes high.

If it all appears to be working (when it does) then maybe it will be ok to run while testing as long as nothing gets warm or hot.

cheers

Tony