My forever scope (BK 1590/Trio 2100) developed a glitch on channel 1. Became very flaky (I know how to do all adjustments, but that is not the issue).
Repsonded to the old TV slap to stop vertical roll though.
I spent the last day and night pouring over the schematics and as I was touching VR1 the trace went haywire. I mean barely breathe on it. So I turned it off, and soaked it with contact cleaner. Turned it back on, was ok but out of adjustment.
As I tried to adjust, the trace went haywire.
So voltages out of IC 1 are also flaky (low). IfI leave the scope on overnight the trace settles down.
In other words, the IC1 ckt is unstable. I am hoping it is the MOSFET since the IC is likely proprietary. (ATM 4010). Cannot get to the pins without removing both the preamp and attenuator board.
I have another story about what happened when I checked a2080 to see if I could swap attenuators. (trials and tribulations story).
Below are the schematics.
THANKS!