Well I'm not sure if a gorilla was responsible for the burnt resistors being lower than 100kΩ, as I discovered the very first batch of HP 5325A's (prefix 820) came with a 82Ω resistor for R3, but this counter is a later 844 prefix and the input amplifier boards have no space for the capacitor C20 that is in parallel with the 100kΩ. I wouldn't normally do this but I decided to modify both boards to match the 844 prefix manual, i.e. how it should have left the factory.
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1151470)
First I had to strip all the components from the burnt areas & clean the carbonised remains away, some Araldite was needed to fill in where one board was damaged.
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1151474)
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The components were all tested, one Zener diode had failed, testing the remaining ones I have decided a 3.3V Zener matches the spec of the rest of them (approx 3.8V at 10mA), one of those has been temporarily fitted & I have ordered a couple of the original 3.83V part as they weren't too expensive (part no. 1902-3059).
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1151482)
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1151486)
I replaced a couple of the resistors that had faded markings, fitted the 100kΩ for R3 and a 1000pF capacitor on the rear of the boards, I also added a link on the back to properly repair a damaged track that previously had a bit of IC leg bodged on.
Both boards tested OK on all attenuator settings, guess I'm lucky the protection circuit did it's job & didn't EOL the dual FET.
![ThumbsUp :-+](https://www.eevblog.com/forum/Smileys/default/icon_smile_thumbsup.gif.pagespeed.ce._JElyJQqdB.gif)
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1151490)
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David