I've received a homebuilt oscilloscope from 1950's. Scuola Radio Elettra, an Italan company back then, was very popular and helped many people to get into the eletronics world. The instruction manual was 770 pages long and it is half builder's manual, half electronics student's book.
The scope does not show a trace on screen. I was told the instrument was OK, but it has been sitting unused for months, to say the least. I read through the manual looking for the troubleshooting section and came across some wisdom on old capacitors.
"The only components that require replacement with use are the electronic tubes and the electrolytic capacitors. If the oscilloscope has been left inactive for a very long time (months or years), it will be advisable to first turn it on for about a minute and then turn it off and let it rest for at least half an hour, then turn it on again for another 10 minutes. After this, let it rest for another half an hour and finally you can use it with peace of mind. This process serves to allow the electrolytic capacitors to reform and regain the efficiency lost during the long period of inactivity."
Even in 1950's when writing the original manual they knew of electrolyic capacitors "hobby" to change their value with time. I assume that "decades" falls into "years" of inactivity, so I will try the procedure reccomended in the manual. With the covers off, so that I see filaments glowing.
