Need help with 561A


n4buq <n4buq@...>
 

I recently bought a couple of 561A's, primarily for the plugins and
to have a good supply of spare parts for my existing 561A. While the
plugins seem to work, neither of the "new" scopes work properly, and
I was wondering if someone might know by the symptoms what the
problem might be.

Both of them produce a rather loud ticking noise which coincides with
a flashing effect in the 6AS7 and the OG3 tubes. Both 6AS7's also
glow a fairly bright violet color and I'm not sure if that is
normal. On one of the scopes, when the flashover occurs and I have
the calibrator hooked up to the input, I get a blur of random traces
on the screen.

I had noticed before that my "good" 561A sometimes would tick like
this, but hadn't traced it to the source.

Is this an indication of power supply problems? I suspect filter
caps simply because of their age, but not sure if this is it. I
haven't bought a schematic yet, so it's difficult for me to do much
analysis at this point. I was just figuring this might be a pretty
common symptom and someone might be able to tell me some things to
check.

Also, still looking for a source for the power cords. Are these now
unobtanium?

Thanks!

Barry - N4BUQ

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