On Sat, Dec 25, 2021 at 09:37 PM, KB2LMN wrote:
Then I test the 55vdc and 110vdc I show an open ¡°OL¡± no resistance.
Definitely should not be reading open. There might have been some charge in the caps that fooled your meter. They should read as a low resistance that increases.
The recommended. but rarely followed, application of tantalum caps calls for about 3 ohms per volt. So caps connected to the 15V supply will be through a 47 Ohm resistor, like R1038. These can hide a shorted cap. I found several in my SC502 that acted as fuses, and some that just sat there and cooked.
You could do a quick test of the horizontal amplifiers by feeding a sine, ramp, or triangle signal into the X input in XY mode and see if you can get a horizontal line or 2 dots with a square wave. Then I'd go looking for the reason that the display always seems blanked except in XY mode.
A bad switch contact is also a definite possibility as Jeff pointed out. And those cam switches may seem intimidating, they are actually rather simple but require a lot of patience.
Dave - AC2GL
DaveH52