[TechAssist] RCA CTC69PF PTV with power supply problems
- From: "John @ Myers TV" <myerstv@xxxxxxxx>
- To: "Tech-assist" <techassist@xxxxxxxxxxxxx>
- Date: Tue, 26 Aug 2003 14:40:37 -0400
RCA Model # P52721LV , Chassis # CTC169PF
Hi gang,
This set originally started with a bad HV splitter. I replaced that to find
that the convergance was extremely distorted. I changed the small board on
the splitter with no improvement. A few seconds later the set went dead.
That's when I began to pull the lightbox, to take to the shop. At that
point, we discovered that a mouse had taken up residence in the convergance
section.
Now, it's a month later, and I'm still trying to repair the power suppply.
The output voltages from the power supply in standby mode are low, &
pulsing. The VCC to U4101 (regulator IC) is fluctuating between 8-10V.
According to the RCA Training manual, this indicates possible overcurrent
shutdown.
The manual also indcates that if I monitor pin 8 of the chip, while
grounding the VCC, I should see the voltage on pin 8 rise a bit from Zero.
I'm not; it is staying at Zero.
Here's what I've done:
I've changed C4118, C4102, C4104, & C4108. I've changed U4101, and CR4118.
I've also changed the filter cap on the reg B+ line (C4141).
The last thing I did was to totally desolder the secondary of the
transformer (T4102). I did this figuriong that would tell me if something in
the set was loading down the supply.
The symptoms remain; It still appears to be in overcurrent shutdown. Oh yes,
I've tried running the regulator from an outboard DC Supply. it runs fine in
that mode, and I have good waveforms all the way to the base of the chopper
output.
Sorry for the length of this post. I don't often get this frustrated by a
169.
I'm open to suggestions.
John Myers
Myers TV Service Co. Since 1984
Alliance, OH
Voice: 330-821-6545
myerstv@xxxxxxxx
http://members.ebay.com/aboutme/tvguy07/
http://members.ebay.com/aboutme/threads_r_us/
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