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31" RCA TV CHASIS C169( Model F31223GG)

 
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sazkazme
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PostPosted: Sun Nov 26, 2006 2:45 pm    Post subject: 31" RCA TV CHASIS C169( Model F31223GG) Reply with quote

TV 31" RCA CHASIS CTC169 ( model F31223GG) HAS a RETRACE LINES some what diagonally ( means not straight), very bright screen, no video but sound. I suspect that VER out SCR (Ref NO.501) is out of service/culprit. THE SCR says 780-7 and on top of of this line is written A23. Thats it . I could not find the datasheet of this SCR any where on the web. Any how I tried to check the SCR. To me it looks thats it is faulty.
where can I locate the datasheet of SCR and Schematic of this TV CTC169 and any expert suggestion by all of you experts will be highly appreciated with lot of thanks. I have very good understand of electrnics but i am not expert one so please help me.
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vtech



Joined: 08 May 2006
Posts: 1264
Location: USA

PostPosted: Sun Nov 26, 2006 8:09 pm    Post subject: Reply with quote

I can assure you that "no video" is not caused by vertical output. So you can pretty much ignore the deal with the SCR--If/when there is a problem with vertical, You'd see a shrunken raster &/or straight line etc.

Bright screen with retrace lines( no video) is more in the area of Luminance/video/blanking. (on rare occasion, may even be caused by pix tube itself) So there is a video problem which can be rather challenging for an even experienced TV tech. --Just make sure the Screen control is not inadvertently turned too high.( can give you the same results)

Do not have the print, however there happense to be a VERY kool interactive training program on CTC169 (Lucky you) residing in the database which is very informative. Tnx to the user who've uploaded it.

On top of page(in the red letter box) type CTC169 then click on "find now" . you'll get to another page. File is actually a compressed EXE in the RAR format at the bottom of the page.
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sazkazme
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PostPosted: Sun Nov 26, 2006 8:26 pm    Post subject: RCA CTC169 Reply with quote

thanks for the Guidance. You are absolutely right the vertical problem is totallt out of question so is SCR.
Yes it is in video. Most probably or tube itself. Because some time blue light is seen sparking at the neck when TV gets warmup. I suspected some carbon flakes inside the tube. What i did i inverted the TV and very gently tapped at the neck. That is gone but the slanting retrace lines are there with broght screen. checked the screen voltage from FBT and i reduced it to minimal but still the problem is there . This problem goes on one direction and that is if i am lucky from pic tube then it is at video driver transistor or some culprit at video/blanking satge. once again thanks for the advice. Mean while if you can further guide, i will highly appreciate. yes I got that software for CTC169 from this site. Thanks for that as well.
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minnie



Joined: 18 Aug 2005
Posts: 2877
Location: Hell

PostPosted: Sun Nov 26, 2006 8:52 pm    Post subject: Reply with quote

CTC169, what's the rest. On a CTC169AT2 I'd have you check C4703 (47uf @ 250V). That causes retrace.
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vtech



Joined: 08 May 2006
Posts: 1264
Location: USA

PostPosted: Sun Nov 26, 2006 9:00 pm    Post subject: Reply with quote

"Because some time blue light is seen sparking at the neck when TV gets warmup"

Aha.. Good old arcing tube. More than likely a heater to cathode short-- while, it is possible to have a problem with a video driver , but it would proly get zapped again on the next arc.
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PostPosted: Sun Nov 26, 2006 10:20 pm    Post subject: Reply with quote

Thanks fo rthe guidance for both of you. I will check the relevant area/parts and will return to you guys for further guidline.Thanks once again.
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sazkazme
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PostPosted: Sun Dec 10, 2006 8:06 pm    Post subject: RCA TC Chasis CTC169AS2( 31" TV) Reply with quote

Hi fellows . Thanks you very much fo rall your guidance and i have been able to fix the TV. The Culprit was Q2906(T148 or NTE32 or 2SA965) IN LUMinace Buffer stage. Teh collector and emitter. which caused +200V at CRT circuit board to drop down to around 170 volt. and apparently it appears that the CRT tube is gone but it was not so. If this 200 volt drops to 18v or zero instead of 178 or 200 volt then you muct check C4703, C4716, R4720 and CR4701. also may be C4713. I am writing beacuse retrace lines in RCA CTC 169 could be caused by any of these reasons most frequently. I used 2SA965 as replacement for T148. Once again lot of thanks to all of you because it was not possible with out your help.
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