I have a frustrating fault with a RM503 CRO.
The CRO is in *really nice* condition, so I would like to restore it to a
My problem is that the Power supply levels are all extremely low. From
memory, the +12V rail is at about 2V, the 250V rail is at about 30V, the
+/- 150V rails are also low at +/- 15V. So, proportionally, they are
correct in relation to each other.
The 500V input to the PSU is spot on.
I have obtained a copy of the service manual, which has helped
considerably. I have tried replacing all of the PSU valves (6DQ6A, 6BL8,
5642, 5651A), as they all looked quite sad, and I had an easily available
tube source. This has not proven to be effective. I have also verified
that all of the resistors are well within tolerance. I have verified that
none of the rectifiers are S/C, and they all drop 0.7V when in operation.
Unfortunately, I am running out of ideas, and am concerned that the
transformer may be at fault.
My questions to the group are;
1) Has anybody dealt with similar faults?
2) How likely is it that the transformer has developed a fault. Where
could I obtain a replacement?
3) Can somebody shed some light on what the normal operating frequency of
the Oscillator would be?
3) Have I missed anything?
I will openly admit that I am of the age where my world is largely
silicon, and that the only valves I have played with before were
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