[TechAssist] Re: RCA CTC69PF PTV with power supply problems
- From: HSWAD@xxxxxxx
- To: techassist@xxxxxxxxxxxxx
- Date: Tue, 26 Aug 2003 17:53:22 EDT
Click on this. Maybe it will help. http://www.wa6ati.com/Ctc169.htm. Hollis
Bates, Field Engineer-retired, Lewiston, Maine, HSWAD@xxxxxxx
In a message dated 8/26/03 4:28:47 PM Eastern Daylight
Time, myerstv@xxxxxxxx writes:
> TechAssist] RCA CTC69PF PTV with power supply problems
> Date:8/26/03 4:28:47 PM Eastern Daylight Time
> From:<A HREF="mailto:myerstv@xxxxxxxx";>myerstv@xxxxxxxx</A>
> Reply-to:<A
> HREF="mailto:techassist@xxxxxxxxxxxxx";>techassist@xxxxxxxxxxxxx</A>
> To:<A HREF="mailto:techassist@xxxxxxxxxxxxx";>techassist@xxxxxxxxxxxxx</A>
> Sent from the Internet
>
>
>
> 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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