I am restoring my neighbors Friden132 and would like to learn how to a) discharge the capacitors, b)analyse electrical problems, c)resolder if necessary,.. etc. to try and at least power the machine up again. The CRT display was one of the first of its kind and displays up to 8 digits I found out.
Ok so I had some help from Chris (also known as 'Tesla-Chris' !) who showed me to test for voltage leakage safely, brought along a gradual voltage meter and figured out where the power blockage/failure was. It turns out the only real problem ws in the mains power supply, and it is up and running on full 220V now,- with a slight leakage into the chassis (source still to be found..)
Yay to Chris!! First device running, almost ready to be shown.
Oh great! -We have several, so will still need to get the others running, so thanks, always good to know there are others out there to collaborate with!
thanks ted, given the age of them, I am expecting them to have to be replaced(?), but until I have learned how to safely 'discharge', I cant really diagnose even their condition. - I found a very useful blog about how the Friden is put together.. in case you are interested..
I'm not an expert, but my understanding is that you may have to re-form the capacitors as well. Electrolytics slowly degrade over time, and you have to re-generate the oxide layer that forms the dielectric after long periods of disuse. I'm not sure of a definitive source of information on the topic; I see some conflicting advice on-line.
The Computermuseum of the Uni Stuttgart is just repairing theirs. You might want to contact them if you need any information: http://computermuseum.informatik.uni-stuttgart.de/