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#181
05-22-2015, 06:55 PM
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Looking at the schematic.. The circuit only consists of 2 ceramic disc caps and two resistors, plus the 100mfd cap off the filter cap which isn't the problem.. I don't know what else it would be other than possibly one of the resistors, or one of the caps which is probably unlikely..
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Looking for an all tube or hybrid color TV set from the late 1960s, early 1970s that's in a steal cabinet.. 
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#182
05-22-2015, 07:14 PM
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I checked the two resistors in the circuit which are rated at (R67) 220 and (R68) 270 ohms.. I get 229 out of the 220 rated resistor, and 195ohms out of the 270 ohms rated resistor.. Testing them in circuit, the one is off by alot, but could be due to being in circuit, and even if it is way off like that, I would still think there would still be contrast control..
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Looking for an all tube or hybrid color TV set from the late 1960s, early 1970s that's in a steal cabinet..
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#183
05-22-2015, 08:42 PM
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doubt the ceramic are an issue, and the resistor values are not critical.
The clue is if you disconnect the can cap and the contrast gets super weak then it pretty much has to be something screwy with the pot/100uf/wiring. you can check other things but that seems to be the case to me.
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#184
05-23-2015, 03:58 AM
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I don't know how to proceed other than to check pin one on the tube socket and check for continuity each end of the wires or just replace the pot if I can find a equivalent part.. The sharp control is also another issue, the wiper and one of the end terminals are bent into each other on that pot and soldered to each other and goes to ground, pot measures very low ohms and meter doesn't go up/down at all the way it's set up, but according to the sams, this is the way that pot is..
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Looking for an all tube or hybrid color TV set from the late 1960s, early 1970s that's in a steal cabinet..
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#187
05-23-2015, 07:54 AM
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lets recap the contrast problem as stated.
Too much contrast, contrast control does nothing. Disconnect the 100uf cap in the contrast control circuit, contrast goes very low colors get "weird" (not sure of what that means or if related). My conclusion is since there are only two things in the contrast control a pot and a large cap, and deactivating the contrast by removing the cap effectively puts the contrast at the other extreme, then the problem HAS to be the cap/pot/wiring one of those are a combo.
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#188
05-23-2015, 01:41 PM
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I'll try the 100mfd cap again, this time I'll tack it on a short wire from the pot control instead of going under the chassis..
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Looking for an all tube or hybrid color TV set from the late 1960s, early 1970s that's in a steal cabinet.. Last edited by tvcollector; 05-23-2015 at 02:51 PM.
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#189
05-23-2015, 02:01 PM
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It's the 100mfd cap... For some reason now it's working.. Last time I tried it didn't work.. Possibly due to the fact I rigged it under the chassis last time, and perhaps maybe when I put the chassis back in the set something may have came loose..
Should I go ahead and just restuff the can? infact I might as well restuff them all..
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Looking for an all tube or hybrid color TV set from the late 1960s, early 1970s that's in a steal cabinet.. Last edited by tvcollector; 05-23-2015 at 02:52 PM.
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#190
05-23-2015, 02:59 PM
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if you have a cap tester you could test the others (old school eye tube type to check for leakage).
IF it checked fine I would leave it and just not use the 100uf in the can. IF any others tested bad (leaky or weak) then I would go ahead and restuf.
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#191
05-23-2015, 03:24 PM
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Am I able to test the cans while they are still hooked up, or does the wires need to be removed to test?
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Looking for an all tube or hybrid color TV set from the late 1960s, early 1970s that's in a steal cabinet..
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#192
05-23-2015, 05:29 PM
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I was looking into the sharp control circuit, I changed out the 6GHA which had a 6LM8.. Now video went away, it's just a grey scale screen.. I inserted the original tubes, and same thing..
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Looking for an all tube or hybrid color TV set from the late 1960s, early 1970s that's in a steal cabinet..
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#194
05-23-2015, 06:39 PM
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Well I give up on the damn thing... All I did was remove and exchange the third video IF tube and the 6G8H video amp and the other 6G8H on the sweep board... I wiggled wires around, and checked the tube sockets, wiggled tubes to see if any change and nothing changes.. I can't get video back.. I get nothing but a grey scale screen with moving retrace lines..
Here's an example: The flickering is the camera.. https://www.youtube.com/watch?v=o7847FdbnBY
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Looking for an all tube or hybrid color TV set from the late 1960s, early 1970s that's in a steal cabinet.. Last edited by tvcollector; 05-23-2015 at 07:14 PM.
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#195
05-23-2015, 08:05 PM
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its best to only do one thing at a time on a working set. That way if something goes wrong its easier to find the problem.
I looks like no signal getting thru the video since the audio is working. 1st is the tube lighting up? sometimes pcb grounds can crack, Need to be gentle when removing tubes. I use a spray lube/contact cleaner on tube before removing just aim around the base and let it set. this way the tube comes out easy and less likely to flex an old pcb. If it was mine I would start with signal injection at the grid of the video out and work back. OR scope the signal begining at the output of the video diode. if you lack the equipment for the above you need to do voltage test and see if the video tubes (video amp and video out) have correct voltage. as to why this would happen, hard to say, most likely a flakey pcb or if you inserted a shorted tube then maybe smoked a plate or screen resistor.
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