[TechAssist] RCA TV F35670MB, CTC187CN3, Lines in Pix

From: gulftech@xxxxxxxx
To: techassist@xxxxxxxxxxxxx
Date: Thu, 23 Jan 2003 18:20:58 -0800

Techs,

I hope and pray someone has seen this and can help.  The set runs great
for about 5-7 minutes.  Then, a 3-inch band appears on the lower third of
the crt.  In this band, the video is distorted by horizontal lines,
almost like firing lines one would see with a flyback arcing except it is
confined to only that one area.  Almost like a UPC code superimposed on
the pix, but turned sideways.

Here is what has been tried.  Please don't laugh too hard.  My tech has
spent two days on this one.  Does not respond to cold spray.
        Tuner ground plane repaired and double-checked.
        Replaced flyback, T4401
        Replaced U1001, LA7610
        Replaced horizontal drive transformer, T4301
        Replaced Vertical output U4501
        Replaced regulator U4101
        Replaced high-ESR cap C4705.
        Replaced C4402, C4407, CR4402, CR4403
Hold on for the fix!!!

Sorry for this long post, but stay with me for the happy ending.  While I
was writing this, I had Tom scope the vertical signal.  The trash was
evident in the signal.  He changed resistor pack R4511 and ceramic caps
C4102 & C4504, both .22ufd.  One of those three fixed it.

There is a point to this long thing.  When I saw the symptom, I knew it
was a first for me.  I told my tech to start with the TGP and go to the
vertical circuit.  He was lost and started guessing--replacing parts. 
When he ran out of parts (guesses), he asked for my help.  I agreed to
write this only if he break out the scope.  Thirty minutes later, the set
is working.  We have all been guilty of this--a time or two at least!

HTH,


Ken Smith
Gulf Technical Services
3034 Gulf Breeze Parkway
Gulf Breeze, FL  32563
850-934-8324 (Voice) 850-932-0819 (Fax)





        

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[TechAssist] RCA TV F35670MB, CTC187CN3, Lines in Pix

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