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Zenith CRT TV - black horizontal bars
Zebidee:
The 1uF caps have pretty high ESR anyway, even when new. According to the tables up to ~5 ohms is good. So probably best you don’t rip them all out. Try comparing esr with your replacement caps. On that same basis, the 1.5uF cap is probably ok too.
romshark:
~5 Ohms may be OK, but the one I read (and posted a pic of) was 1.38 Kilo Ohms = 1385 Ohms.
Took me a while to get my head wrapped around the metric units part. This meter usually shows good caps in milli-Ohms (so mΩ on the display).
Zebidee:
Lol wow I was reading from phone, didn’t look close enough to mentally register the “k”. Yeah 1.38k ohms is high by any standard! Anyway, yes that’s obviously a bad cap.
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romshark:
So the capacitors came in today from Digikey, and I spent the night replacing the suspect ones, and some of the other ones too.
Got everything hooked up and...still the same exact problem. At least I didn't blow anything up with a backwards capacitor.
So I'll wait till the weekend, discharge it, and take a look at the board again.
Did some further testing while it was hooked up:
Before I said the bars were based on the brightness setting. I was wrong; it's actually the contrast setting. Turning it higher causes the bars to darken compared to the rest of the screen. Turn it low enough and the bars disappear. The picture is a lot darker than I'd like when the contrast is set that low though (definitely darker than I played back in the day.)
Also tested my Sega on an RF connection (I had done all my previous testing with AV cables.) My thinking was that, if the image is normal through RF, then it may be one of those many capacitors near the AV in. However, the problem looked just the same on both connections.
I'm going to give it some more work, but I may eventually cut my losses, and check the neighborhood forums (yes, we have that) for a CRT TV that someone may want to part with. At this point, I'm thinking it may not be a capacitor-related problem after all...
Zebidee:
Sorry if this is an obvious question, but have you tried tweaking the screen voltage knob (usually on flyback) at all?