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RCA CTC187CN2 retrace lines   Goto page 1, 2  Next  
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Don
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PostPosted: Sat Jun 16, 2007 10:58 pm    Post subject: RCA CTC187CN2 retrace lines Reply with quote

Hello all, the picture is poor, washed out fuzzy, with retrace lines, I found the following caps open C4404 C4709 and C4127 but replacing them did nothing, still bad pic w/retrace adjusting the screen on the fly also does nothing for the retrace lines. The retrace lines are bowed in on each side of the screen so I checked the pincushion diode CR4403 and it checks good but Im wondering if it is failing under load, then I found the following caps to have high ESR C855 (2.2/50v bi pol) C854 C853 C862 and replaced them C851 also bi pol checked good, last I replaced C5003 on the CRT board, it also tested with a high ESR. I also soldered inside the tuner.
Nada! Still same pic and bowed in retrace lines, any help is appreciated, I remind everyone I am working without a scope.
Don
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Jim
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PostPosted: Sat Jun 16, 2007 10:58 pm    Post subject: Reply with quote

Don,

Did you check C4703 (47 mfd, 250V)? Also C4501 (.22 mfd, 100V). The CRT
socket could have leakage.

Jim
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PostPosted: Sat Jun 16, 2007 10:59 pm    Post subject: Reply with quote

Ok C4703 was also replaced and I forgot to mention C4407 was also replaced. The .22mfd 100v cap you mention is C4504 on this board not C4501, it test's good but I replaced it any way, I did not have a new one but took it from a board that had a different problem.
I soldered the socket, what goes wrong with those?
Anyone with any other ideas?
Don
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PostPosted: Sat Jun 16, 2007 10:59 pm    Post subject: Reply with quote

Check luminance buffer Q2901.

brian
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PostPosted: Sat Jun 16, 2007 10:59 pm    Post subject: Reply with quote

Don, Check out your video buffer Q2903 off pin 6 of the ic 2901 Micro. Also
check your T-Chip U1001 Pin 44 is Y out Should be around 4 volts, Q3304
Video Buffer (3.4 volts on the emitter and 11.4 Volts on the collector .
Video Amp 3303 .



John
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David
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PostPosted: Sat Jun 16, 2007 11:00 pm    Post subject: Reply with quote

Don, I stand in agreement with Brian, I have sent the luminance buffer cause
this problem many times. But I've never seen this transistor cause the
bowing problem you describe. You'll find this transistor near the back of
the PCB.

David
Don
Guest





PostPosted: Sat Jun 16, 2007 11:00 pm    Post subject: Reply with quote

Ok guy's there is no Q2901 on this board, nor a IC or U2901. CTC187 "CN2"
Don
Jim
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PostPosted: Sat Jun 16, 2007 11:00 pm    Post subject: Reply with quote

Don,

Answering your question about the CRT socket. Sometimes the screen voltage
leaks to the spark gap on this model causing a bright picture with retrace
lines, and requires replacement of CRT socket.
Guest






PostPosted: Sat Jun 16, 2007 11:01 pm    Post subject: Reply with quote

What about Q2903?
Guest






PostPosted: Sat Jun 16, 2007 11:01 pm    Post subject: Reply with quote

Ok, there is a Q2901 and a Q2903, what I didn't realize was that they are on the "underside" of the board and are "micro" componants. I dont have these in stock and Im not making much on this to begin with so if this dont work with what I have done so far I am calling it quits on this one.
About that CRT socket, is there a way to tell if that is the problem without actualy replacing it?
Don
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