5111 Storage Scope Loss of -30VDC


Bob Wilson
 

A friend gave me this one saying it had never been used. It still had the little paper stuck on the CRT saying how to power it up if it had been off for over a month.
But of course it did not work correctly only having a small dot on the CRT that bounced around.
I eventually found -30 VDC was missing and replaced a shorted 1uf tantlum cap on the storage board. But still no -30VDC.
If I disconnect the -30 VDC wire going to the storage board the voltage comes up. So either the supply is weak or something on that board is pulling the voltage down.
In testing the transistors on the storage board I find some kind of stuff in the socket holes. Maybe thermal compound, I don't know. But now its hard and makes getting the transistor lead difficult to reinsert back into the socket. The TO39 transistor all check good but I have not gone throught the TO99 transistors yet.
Any suggestions would be appreciated.

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