#16
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Thanks M
something's goofy in the IF as I wiggled all the IF tubes and the picture came back, I'll check the solder joints and clean the sockets tomorrow, but it's playing fine now....... |
#17
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Yaargh! this TV is frustrating...... it seems the vert/horiz is locking but the washed out contrast look goes in and out, but can sometimes be "fixed" temporarily by jiggling the channel selector.
I might try injecting video past the detector diode and rule out any problems there. I'm still thinking the tuner might be troublesome, but the card edge connectors at the back of the PC board might be problematic, but I've cleaned those several times. I have cleaned the tuner, but I've been gentle (maybe too gentile) trying not to screw it up. |
#18
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When I clean a tuner I use De-Ox-Id and a white rubber eraser...The De-ox loosens the crud and the eraser gently scrubs it off and polishes the surface...Hasn't failed me yet. There is something nice about seeing a black terminal become completely shiny metal once more.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#19
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Well I feel dumb. I found another 3BU8 (agc keying/sync sep/noise limiter) in my tube stash and swapped it in and the picture is back. I woulda tried this earlier but I hate throwing tubes at a TV set.
The tube tested ok in my tester, but it was slow to get into the green zone |
#20
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Quote:
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
Audiokarma |
#21
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Quote:
IIRC, the circuit is a Zenith design, as they used it first. |
#22
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Working on tvs/radios...etc since the early 70, s in my basement shop for a large part of my career (made more working for myself)(tough to keep new stocked tubes) i used pretested in tvs or whatever used tubes i knew were good in a set.saved me a LOT of trouble.i would recommend that any tube set every member has in this forum,stock used tubes tested on a tube tester AND tested in your known workining (or once you got it working sets. A lot easier. Maybe this should be a stiicky post. RonL
Last edited by ronl; 10-18-2018 at 06:24 AM. |
#23
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Well the sync went funny again. So I pulled the board and found a crack in the ground plane trace around the edge of the board (near the horizontal output tube - high stress area), solder bridged it back and got sync again
The sync circuit must have been dropping the ground there intermittently. Now the horizontal linearity is a bit off, but I screwed up the noise gate (sync stability) pot so now to fix that..... |
#24
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Quote:
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#25
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This ol' ball of wax again.
I'm having problems with the horizontal, barely able to hold a steady picture, and I have determined the voltage is too low on the horizontal oscillator tube due to out of spec resistors in the horizontal sweep couplate. I have built simple couplates in the past using perf board, but these are some stacked up monstrosities with 12 pins. Anybody here attempt to make one of these? I'll likely try to build the new ones similar to how the old ones are made..... |
Audiokarma |
#26
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Aah, the mil spec couplates (there is a YouTube video of their manufacture out there), I've never changed one, but I've seen them in gear once or twice, and have a couple nos specimens....it probably has fewer parts than legs which might simplify construction of the replacement.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#27
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Here's a schematic of the two of 'em in this TV. The bad one is the horizontal but I'm going to redo both of them.
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#28
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Quote:
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#29
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+1.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#30
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Definitely replace the dual diode if you got horz sync issues that subbing the tube don't fix.
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Audiokarma |
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