The A sweep start and B sweep start waveforms are off, and I am working on solving that. I am fairly certain that the issue is originating from the trigger gen circuit. I also cannot reliably do any kind of voltage measurements or waveforms that rely on any output from the vertical preamp other than directly thru to logic then the vertical amplifier, and I am waiting for the parts to fix it. (151-0333-00) they should be here monday according to USPS, but who knows.
The rotten apples are Q154 & Q155, and are not properly amplifying the input signal. The DC voltages are spot on or very close, but once signal is put into the scope the waveforms up to TP5 & TP6 are good, but those two are 1.5V low and their waveforms are 10% to 20% low as well. If replacing those does not fix it, then it's CR258 & CR258. But the problem is almost the exact same on both channels, so I believe it is the transistors.
Also I had mentioned that the input JFETs are likely on their way out. I am not 100% certain on this. I could only get one new 151-1032-00 (only one I could find--- ANYWHERE!!) from Greece. However, according to the following site:
http://www.reprise.com/host/tektronix/reference/transistor.aspthat dual JFET is the exact same as the 151-1090-00, so I may order some of those. I'm also looking into buying a 464, 466, or 468 parts scope.
Speaking of JFETS, I received my 151-1042-00's for the trigger circuitry.... but.... I have 8 matched but mixed up pairs to re-match, and one proper pair but TO-106 package. I think that their stripes are painted after they are matched, but I still think I should build a test circuit to confirm, such as this one in Post #9:
https://www.eevblog.com/forum/projects/how-to-match-a-set-of-jfets/Then once I have the input to the trigger circuit back in order I could work on the sweep and some of the z-axis. unfortunately the horizontal amplifiers voltages are taken in XY mode so I can't do that yet.
At least I'm gaining momentum!!! this definitely is a beast of a repair/refurb for a beginner's learning project, but I'm gettin the hang of it!
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