CTC169 frustration

[DHT112A]

"I have a 35" Proscan 35123 direct view TV with a CTC169EJ5 board.
Manufactured in March of 96. I have replaced all the recommended parts
in the power supply and all voltages during idle and run are right on.
The original problem was a shorted HOT which was replaced along with
Q4302, Q2906, C4401, C4402 and C4403. I have had the flyback out and
it's resistances seem OK. A couple of times during the power supply
rebuild I put the board in the TV to put it in run and check some
voltages. When I turned it on it only had a bright narrow band across
the screen. Sound has always been fine. I tapped the flyback and it
came back to full screen. I have replaced Q4201 and Q4202 seems OK.

When the power supply rebuild was finished and I thought all was well
and we sat down to watch it, the thing suddenly popped through the
speakers and shut down. It does not try to restart but can be turned
back on by remote or power button on front panel only to pop and shut
down again. There is no certain time for shut down. It may be a
minute or two or just seconds. I see no burned, bulged or obviously
bad parts. The voltages don't appear to jump before shut down so I
don't think it is over voltage. The 143 volts at CR4116 drops then
comes back up in standby.

Now the picture has gone to a bright narrow band all the time with the
antenna hooked up and a dim thin rainbow colored football shape without
antenna. I have replaced U4501, CR4504, SCR501, Q4507, and Q4505. I
have checked the voltages in this area. All are good except pin 6 and 1
on U4501 are dead. All voltage around Q4801 are dead and there is no
voltage at the B and E on Q4803. The only thing I could find was a
cold solder joint where the yoke wire was hooked to the board causing a
resistance between the yoke connector and connection on the board. The
yoke resistance checks good.

The funny thing is it will stay on indefinitely while no antenna is
hooked to it but put the antenna on so it would have sound and picture
it pops and shuts down.

I plan on doing what I can but I have no scope. I have experience
building tube audio amps and understand tubes well but don't know much
about sand(transistors).
Any advice anyone can give will very much appreciated.

 

[[email protected]]

Check value of R4526 off IC4501. Resolder resistor legs and see what
happens. Good luck.

 

[DHT112A]

Check value of R4526 off IC4501. Resolder resistor legs and see what
happens. Good luck.

Resistor R4526(6200ohm) is good and solder is good. Thanks for the
response.

 

[Shoreline Electronics]

Your flyback may have an open winding. I had this exact same chassis with
this problem.. Looky here!


If this doesn't do it , can you post a photo of the fault on the web
somewhere?

---------------------------------------------------------------
Text pasted from WinSTIPS 2.0
http://www.ServiceSoftware.com
---------------------------------------------------------------

RCA CTC169EJ5

Raster Squashed Vertically. Has Osd But No Audio Or Video.

Jeff Stielau : 8/2/99 : Shoreline Electronics

Check -12v Supply Off Pin 7 Of Flyback. If It Measures +4vdc Or Something
Odd, Check For Open Pin 7 On Flyback

---------------------------------------------------------------



--
==========================
Jeff Stielau
Shoreline Electronics Repair
344 East Main Street
Clinton,CT 06413
860-399-1861
860-664-3535 (fax)
[email protected]
========================

 

[Jason D.]

Your flyback may have an open winding. I had this exact same chassis with
this problem.. Looky here!


If this doesn't do it , can you post a photo of the fault on the web
somewhere?

TV trying to power up and get a POP! from the speaker is classic dud
flyback arcing inside causing tv to shut down with a POP. Get one
from RCA use your full service model # to get correct part. The
flyback location is T4401.

Sometimes this takes awhile and cost pretty penny too. Some of these
parts may be NLA due to this chassis age.

Watch out for those hot glue slathered all over the components!!! It
caused the solder joints to fail.

Cheers,

Wizard

 

[kip]

Did you resolder that BIG blue box cap I thinks its a .99 or something like
that.

kip

 

[DHT112A]

It is 1.54uf cap and I had it out to check capacitance along with the
2200uf cap and both checked ok. I have been over this chassis several
times with a magnifying glass and found two bad joints caused by the
glue which were resoldered to no avail.

It does not try to start. It does start and will run for a while
before shutting down.

I have, since the original post, replaced the jungle chip Q4505 and
capacitors C4504, C4518 & 19

I have come to a conclusion it must be the flyback even though the
windings all check OK. I saw a small wisp of smoke one time but cannot
isolate where it came from. It came out from behind the flyback from
where I was looking at the chassis. There is no smell and no burned
parts. I am expecting one in the mail today.

I would have never paid someone to do this. I am learning a lot about
this sand and I figure I can throw a lot of parts at it versus buying a
new one of this size.

 

[kip]

Ok Fine let us know when the Flyback is installed.

kip

 

[JURB6006]

After all your work, if something really wierd happens, you'll pay.

If it works after the smoke comes out, you probably have a fried small disc
capacitor. Doesn't affect the tuning of the H sweep all that much, but fine
tunes it. Anything else burns it is either shorted or open. Of course this is
now open.

Is the geometry PERFECT ? I mean perfect.

JURB

 

[jesusL77]

Pretty new to this Proscan repair stuff... sorry about not being able
to help on the repair, i trust you have an answer by now....

i however have a question for you...i need to
replace the vertical damper diode CR4504(as indicated on the parts
list) and possibly
the horizontal yoke capacitors.. i have searched the board and the best
i can
do is find a CR504?... any help as to the location of the CR4504 would
be appreciated... thanks

 

[DHT112A]

The CR504 is the CR4504. They leave off the first number on the board.