Hello to the mindhive. I bought some time ago 475 but unfortunately the channel 2 was all weird. I narrowed it down to few problems which I'm tackling one by one.
There was failed 100x attenuator so I sourced a new old stock replacement via eBay which arrived with the lid barely holding on the module. That wasn't too much of a concern the trouble started when I tried to put it in the lacquer holding the trimmer capacitors flaked off and all the compensation and functionality is gone.
Is this a common failure node for new old stock parts? It looks like I need to buy another one for sure but how do I "re-glue" It to make it reliable for the future?
My current thinking is to apply another layer of conformal coating over the top, that should hold it for few decades? What I am not sure about is to what extend could the conformal coating change the properties of the attenuator at 200MHz.
There is another issue with channel 2 even on the working attenuator ranges but I haven't had time to dig deeper down into that one. I suspect the input amplifier is shot, I will deal with it later.