Someone donated this to me a while back. The voltage / div controls were noisy and
the trace drifts randomly, so I cleaned up the wafer switches today and the controls are less noisy
but theres still drift on both channels.
The drift seems worse when you do the mag x10 pull on the knobs, eventually the trace floats
all the way off the top of the crt, usually when measuring something. If nothing is measured,
and its set to gnd, theres mostly negative drift, moreso if you tufn the knob to lower div settings.
Someone linked me to this post:
https://www.electro-tech-online.com/threads/2n30809-dual-fet.104271/?highlight=#post851692Apparently those FET's are a common problem, then he I guess isolated an issue with a Hybrid encapsulated IC
which is likely unobtanium.
When the scope is on a short time, the issue is not very prevalent, but seems the longer its on the
worse it is so it could be heat related.
2N3809 (Q23a/b) looks like a typo on the drawing (pg 38/39). Not sure if thats a dual FET....symbol looks wrong.
I found an Analog devices AD3956 as a sub and installed but still have the same issue.
Someone said possible leaky caps are allowing DC into the mix...anyone seen something like this before and resolved it?
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