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Hi!

I got two non working 7603 so I’m trying to get at least one of them to work.
Just got one of them (which is in very good external shape!) for free from a very friendly man here in Sweden who has a huge collection of electronic stuff.

The one I just got had a faulty power supply so I’ve borrowed a few parts from my other 7603 got good results for the +5, +15, +50, +130, -15, and -50, they are all well within specs. But I got nothing showing up on the CRT.

This is what I got when I look at the horizontal deflection plates:


What’s the next step? Swap some boards from the other 7603?

I mainly work with guitar amplifiers so I don’t got much experience working on scopes but I got some “basic bench equipment” and can measure up to 30kV if needed. ?


All the best,
Henric

www.facebook.com/hermanssonamplification

Henric,
I once had a 7603 with a problem intensity circuit. Turned out to be a failed transistor. .
Bob

I realized that I didn’t see any CRT filament/heater glow in this newer 7603 so I put the working PSU in the other 7603 and in that scope I see the CRT is glowing. I can see a dot on the CRT screen for one second the moment I start it up then it’s gone. Got nothing on the horizontal deflection plates on this other older beat up 7603.

I would really like to get the newer 7603 up and running since it’s in very good shape and if got the readout board which my other 7603 is missing. I’m planning to use my 7L5 (which I was lucky enough to score on eBay recently) in this 7603.

I’ve replaced the CRT in the older 7603 before (it was cracked when I received it) and hoped that was the only problem with it but when it had some other issues and since it was lacking readout option I didn’t spend any more time on it.

Anyone who knows a spot where I could measure the 6,3VAC filament/heater for the CRT? Looks like it’s elevated almost 3kVDC above ground?!