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  #46  
Old 09-01-2017, 05:40 PM
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The audio amplifier is acting stupid now though. Ocassionally, it will start humming and popping regardless of which function it's on. TV, radio, or tape. It's extremely annoying, especially since it happens randomly.
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  #47  
Old 09-01-2017, 07:29 PM
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Quote:
Originally Posted by Jon A. View Post
If it's a 70s set it's most likely to be VERY early 70s with a T940 chassis. If late 60s, probably T933.

I guess we'll never know. I'm out of here.
Dave - all these problems, and still no chassis number posted.

With one post, you could have folks looking at their Sams Photofact folders, seeing markups on the Sams for various problems/cures for the color, sound, etc, and possibly have had the set working 100%. Is there no chassis number to this set?

Tons of resources are available. Heck, even American Radio History has all those PF Reporters, Electronic Servicing, and Electronic Technician Dealer magazines with lots of "SYMCURE" problem/solution help, but the search engine wants........a chassis number.

Exhibit one: http://www.americanradiohistory.com/...al%20digest%22
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Last edited by Findm-Keepm; 09-01-2017 at 07:44 PM. Reason: added link
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  #48  
Old 09-01-2017, 09:54 PM
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T951
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  #49  
Old 09-05-2017, 06:01 PM
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Color went out again. It worked perfectly a whole 6 days.
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Last edited by TUD1; 10-20-2017 at 12:02 PM.
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  #50  
Old 09-06-2017, 09:11 PM
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Looks sweet.

I have always wanted a console but have not had the room for one.

Enjoy it!!
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  #51  
Old 09-07-2017, 11:43 AM
dieseljeep dieseljeep is offline
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Quote:
Originally Posted by TUD1 View Post
Color went out again. It worked perfectly a whole 6 days.
Did you hit the color killer control and a few others with contact cleaner?
Those controls were never touched in normal operation! It seems like that chassis was the last all tube model Magnavox made. That chassis, almost changed my attitude toward Magnavox, they were rock-solid. They must've got all the bugs out, in that late production.
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  #52  
Old 09-07-2017, 12:51 PM
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Since the color comes and goes at the drop of a hat, I've decided to just stop caring when it breaks or fixes itself. It popped back in yesterday. Yes, I hit the color killer control with cleaner. Whenever I get a new set, every control and every tube socket get DeOxit.
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  #53  
Old 09-07-2017, 01:44 PM
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I pulled my Dad's Sams 1180-1 folder - man that schematic is huge. C760 is circled with "no chroma". Looking at the pix of the main video/chroma board, the cap is a polystyrene cap - silver foil with clear body. My guess is heat kills the cap, which is right after the last Chroma Amp, before the demods. If you decide to replace it, it appears to be the only polystyrene cap on the board, and is on the right side (looking at it from the back of the set), halfway between the 6MK8 Z-X demod tube and the 6GH8A Oscillator, and is next to a stand-up adjustable coil. Replace it with a dipped silver mica - 220pF, 300V or more.
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  #54  
Old 09-07-2017, 07:03 PM
Bill R Bill R is offline
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I have seen problems with the tube sockets as well. Not necessarily oxidation, but loose connections to the tube pins, and broken connection in the socket. It might be worth changing the tube sockets on the chroma board. At least the color killer and bandpass amp sockets.
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  #55  
Old 09-07-2017, 09:06 PM
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Originally Posted by Bill R View Post
I have seen problems with the tube sockets as well. Not necessarily oxidation, but loose connections to the tube pins, and broken connection in the socket. It might be worth changing the tube sockets on the chroma board. At least the color killer and bandpass amp sockets.
If you do - be forewarned - the phenolic boards are super brittle and heat+torque can easily break a board. My tactic has always been to minimize any mass before desoldering the socket by clipping out as much of the socket as possible from above, and removing the individual pins, letting the board cool before desoldering the next pin. This places less stress on an already stressed board.

Likewise, when soldering in the new socket, go slow and allow the board to cool before plugging in the tube - the socket will be tight, and any flex may break or crack the board. Been there - done that, and finding a donor set was a pain.

Any Predicta owner knows the brittle board syndrome well - all that heat and age equals problems.
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