Hello everyone,

Until last night, my experience with the used Tektronics 475A =
oscilloscope I recently bought on eBay had been only positive.  But =
yesterday, when I powered it on, the whole screen lighted up, then =
started blinking at a rate of about 1Hz.  I've never seen it do anything =
like that before, so I tried adjusting the knobs.  For about five =
seconds, there was a diagonal line going across the screen, then it went =
blank. =20

I turned off the instrument, let it sit for a few minutes, then powered =
it back on.  A dot appeared in the center of the screen, and it stayed =
that way since.  When a signal is applied, you can see a vertical line =
whose lenghth is proportional to the amplitude of the signal.

Tektronics discontinued this model in 1985, and I couldn't find any =
information about the scope on their website, except that it had now =
been replaced by the TDS380.  Searching the web produced no results =
either.

I know that Dale and a few other people owned (or still own) the 475A =
model.  Can you guys give me some pointers on where to start?  I don't =
feel comfortable getting inside the scope without some kind of plan..

Sincerely,

Vitaliy

P.S. There is a *possibility* that the scope suffered some thermal =
damage, because I accidentally covered up the ventilator hole in the =
back of the oscilloscope..

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