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#1
05-07-2024, 10:09 PM
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I worked on a TON of these back in the day.
First things first. Do a visual and check for the obvious; poke around and look for overheated components, wires, etc. Go under the chassis in the power supply section. If the set has any time on it you will find corroded solder joints, bad/ ready to fail solder terminals, resistors, etc. Those power resistors generated a LOT of heat. It’s best to remove the power resistors from the terminal strip, sand the leads clean and clean the terminal strip lugs. If you’re lucky you’ll succeed. If not, replace. Replace or re-stuff the canned electrolytics. If they are the originals they can (no pun intended) go at any time. As previously mentioned, re-solder every circuit board’s ground lugs. Without a good power supply you have nothing. Also, have you checked the tubes? Once sure the basics are present, you can tackle the rest. Last edited by reeferman; 05-08-2024 at 11:35 AM. 
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#2
05-09-2024, 11:23 AM
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WOW, this BBS sure has been glitching out a lot lately!
 
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために
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#4
05-09-2024, 01:48 PM
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Quote:
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So many projects, so little time...
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#5
05-09-2024, 01:58 PM
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Quote:
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために
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#6
05-10-2024, 01:01 PM
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Back in the day we tried an isolator a couple of times. It smeared out fine detail in the pic due to parasitic capacitance-to-ground (since video goes in via the cathodes). Don't recall ever trying it on a rectangular tube, though it might do better due to the unit's smaller size.
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#7
05-10-2024, 02:11 PM
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What does an isolator do really?
Cause it seems that the CRT already has it's own winding off the main power transformer separate from everything, save for a pull up to 200-300v, is it not already isolated by that heater being powered that way? Or is this isolator removing that path to the pull up and any ref to ground through it?
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために
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#8
05-10-2024, 04:58 PM
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OK I didn't read your post well enough. Separate winding on power xfmr. Dumb senior moment! DOH.
 Parasitic capacitance would still be a problem though.
Last edited by old_coot88; 05-10-2024 at 05:35 PM.
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#9
05-10-2024, 07:57 PM
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The CRT filament usually shared its power transformer winding with the 6BK4 high voltage regulator tube. There was usually a .1 cap to ground from the semi- floating filament circuit. When needing an isolation transformer because of a heater to cathode short in one of the guns, removing that .1 did help with the smearing issue sometimes.
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