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  #16  
Old 08-08-2016, 10:34 AM
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Quote:
Originally Posted by jstout66 View Post
Nice set, but I learned those are one of the FEW sets of that era where you really DO need to recap the boards. I can't remember the brand, but Motorola used some really crappy caps, IIRC they are brown, and those boards gave us fits in the 80's. It was not the mindset of the era to even service the boards, but to simply exchange for rebuilt. Good luck with the set tho.
Do you mean the brown tubular film caps (or paper?), or the electrolytics? I'm restoring one of these too, and intend to test and replace all electrolytics, but the brown plastic ones seem suspiciously like paper capacitors. Gotta pull some and test for leakage current.
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  #17  
Old 08-08-2016, 11:21 AM
jstout66 jstout66 is offline
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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)
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  #18  
Old 08-08-2016, 11:31 AM
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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.
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  #19  
Old 08-08-2016, 02:35 PM
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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
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  #20  
Old 08-08-2016, 03:04 PM
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I measured HV before and after the picture faded out. 24 KV the whole time.
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  #21  
Old 08-08-2016, 05:03 PM
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Quote:
Originally Posted by TUD1 View Post
I measured HV before and after the picture faded out. 24 KV the whole time.
I think he means CRT heater voltage and any other tubes in the set (some WID sets had ~4 tubes in them).
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  #22  
Old 08-08-2016, 06:30 PM
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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.
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  #23  
Old 08-08-2016, 06:52 PM
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Time for a can of freeze spray....
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  #24  
Old 08-08-2016, 08:18 PM
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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
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  #25  
Old 08-08-2016, 10:46 PM
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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.
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  #26  
Old 08-09-2016, 11:29 AM
dieseljeep dieseljeep is offline
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Quote:
Originally Posted by zeno View Post
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
Motorola's used a 3AT2 or a 3BT2, HV rectifier. The old TS915's were really reliable, but they had their quirks.
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  #27  
Old 08-09-2016, 05:18 PM
centralradio centralradio is offline
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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  
Old 08-09-2016, 05:21 PM
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Quote:
Originally Posted by zeno View Post
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
So they were the first that came up with the PITA switching power supplies in TV's.
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  #29  
Old 08-10-2016, 12:16 PM
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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?
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Last edited by TUD1; 02-14-2018 at 12:18 PM.
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