#16
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#17
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the tubular film ones. You wouldn't think they would be bad, but they have issues.
As for a recap, if you are comfortable with it, do all the boards. If yours has a specific problem, recap the board that would cause the problem, and see how it goes. It's been MANY years since I've been in one of those, so hopefully a MOTO person will correct me on bad info, but wasn't the main board that always caused issues the JA board? (can't remember if that's the name of the board anymore) |
#18
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Good to know. That look like brown versions of the old black beauty capacitors from the fifties which are often bad. This TV really was made at a time of change, all those old tube era parts mixed with silicon transistors and modularized construction. Thanks for the heads up!
I have tons of film caps, I got a couple bulk orders from China eBay sellers. I'm going to try and replace everything suspicious. |
#19
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Slow fades then slow brightening of px often the
filaments loosing volts. Just see if they are changing. HV rects were about the only thing that went on them in the olden days, sometimes yearly. IIRC they used a 3A3 & some times a 3CU3 or 3DB3 ?? And dont neglect module contacts, usually can smoke them out with light poking & tapping. 73 Zeno |
#20
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I measured HV before and after the picture faded out. 24 KV the whole time.
__________________
"If you wish to make an apple pie from scratch, you must first invent the universe." -Carl Sagan |
Audiokarma |
#21
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I think he means CRT heater voltage and any other tubes in the set (some WID sets had ~4 tubes in them).
__________________
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 |
#22
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I was just clarifying that the HV does not change. The CRT filament is also lit when the picture fades. I'm beginning to think some component is drifting and causing the bias voltage to go up as if the brightness control is turned down.
__________________
"If you wish to make an apple pie from scratch, you must first invent the universe." -Carl Sagan |
#23
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Time for a can of freeze spray....
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#24
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JA board was the first switching power supply for a
TV as far as I know. Lots of fails & we didnt understand how it worked early on. Used in the 2nd gen WID sets but not the Quasar 2 or portable hybrids. 73 Zeno |
#25
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There are three transistors on the L module that I will be turning my attention to next. They have to do with the brightness limiter.
__________________
"If you wish to make an apple pie from scratch, you must first invent the universe." -Carl Sagan |
Audiokarma |
#26
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Quote:
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#27
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I agree.Change the electro caps and see what happens.I remember these sets have those orange electro caps on the modules.I got to do the same thing in my two portables when I can dig them out of the dungeon.
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#28
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So they were the first that came up with the PITA switching power supplies in TV's.
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#29
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I am quite astonished that the CRT in my Motorola tests as good as it does. After I C&B'd it with my 470, it checks nearly brand new. It has just as strong emission at 4 volts, as it does at 6.3 volts. Don't believe me?
__________________
"If you wish to make an apple pie from scratch, you must first invent the universe." -Carl Sagan Last edited by TUD1; 02-14-2018 at 12:18 PM. |
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