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#1
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I found CR3205. I should hang off that to check for 150 vdc at c of hot? What is c of hot? Sorry, just can't think straight. Also, i can't locate CR3473. Wanted to mention a blue wire coming down from the yoke with a red wire has burned at the end where it plugs onto the HV board. red is fine. trying to test today and smelled burning.
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#2
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Yes for 150V use anode of CR3205 as ground.
CR3473 on main board ( 9-214 ) ??? Left of main filter cap & a stand-up power resistor. Use cold ground for that. Fix zorched yoke wire now, if you are lucky its causing shut-down. 73 & merry Christmas Zeno |
#3
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I'll look and see what I have tomorrow. (It's dark here.)
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Bruce |
#4
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Ok, i'll be on here again tomorrow.
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#5
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I dug out the manual for the cheep model
of that year. Same basic design but lacking features like comb filter, jack pack, better audio etc. Start process. Relay closes, applies 150 VDC to HOT & that little board. The little board has a multivibrator that drives the HOT base. This gives some HV. A winding on the flyback ( FBT ) is rectified by CR3473 & gives 25 volts to the hoz drivers. Also goes through R3464 12 ohm 10 W to Q3437 the 12V regulator. As the 12 V comes up it starts the hoz osc & the set is in the run state. If any of the chain breaks that 2 K resistor usually will burn. Like most sets this one has two grounds for measuring DC. HOT GROUND used for HOT & multivibrator. Use the anode of CR3205 on HV board for measurements. COLD GROUND use the CRT ground or IF shield for measurements. This is for almost all other DC grounds. For now check for 150 VDC at C of HOT using the hot ground. Then turn off set, wait a few minutes, hang the meter on cathode of CR3473 & cold ground. Turn on WHILE WATCHING meter. It will either go up & stay up, never go up, or go up then quickly down. 73 Zeno |
Audiokarma |
#6
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The arc is due to carbon build-up there at the contact point. You've got to get rid of the carbon. Cut it away, as necessary.
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Bruce |
#7
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Ah, ok. then everything should work afterward? I'll clear away the bad area and post again.
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#8
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Success! All it was carbon buildup whete it was arcing. apparently, the whole failure was the blue yoke wire arcing and causing the burned area. i had fixed the wire last year and didn't know about the carbon causing this. cleaned with a brush and cut away the affected srea and she started right up. been running about 10 minutes now. gonna hook up a vcr and see how we look. thanks to all those who helped. awesome people on here. ill also pist up ics when i can and update on the cabinet repairs as well.
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#9
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Yay! Zenith!!!
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Bruce |
#10
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The knowledge on this website is fantastic!
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Audiokarma |
#11
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It sure is. Zenith is tough!
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#12
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Nice work, I knew you could do it ! If that CRT is good
you will be treated to a real fine pix. Now go get another set & we can have more fun !!! 73 Zeno |
#13
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#14
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Congrats! Those 80's set deserve to be saved as much as those of the 70's or the 60's in my opinion! Be sure to keep us posted about your cabinet restoration also!
Big thanks to Zeno on this one also! |
#15
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I Agree. They should be saved. colors seem a bit rich though. especially, red and blue. all colors show up well on everything and the clarity is good. watched several movies on it last night. Hopefully, i'll start on the cabinet after spring.
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Audiokarma |
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