Panasonic TR-4CT5 Help

[rodrigo...@gmail.com]

I love old electronics and recently purchase a Panasonic TR-4CT5, it powers on and volume text is normally bright. Just have issues when I plug line in. Brightness of the input is fine for a minute then fades to super dark.

Volume label stays at right brightness so I figured it;s not the CRT or brightness, feel it's a capacitor somewhere or something to do with the video input as on UHF noise is OK and doesn’t fade dark.

I scoured google for a manual or service manual but I could not find anything.
Any help or guidance would be appreciated as I think it’s an electronic I really want to conserve.

Thanks guys

[John-Del]

Yes, it's always a capacitor...

Get the numbers off any IC you can find and get the datasheets off the web. The datasheets will tell you what they are and what the inputs and outputs are as well as what voltages should be on the Vcc. Unless it's mostly discrete transistors, datasheets are almost as good as a schematic.

With some searching, you may be able to identify another Panasonic model that might be virtually identical from a chassis standpoint, and you might find the schematic to that.

[tabb...@gmail.com]

can't work out what you mean at several places. It doesn't sound like a bad electrolytic capacitor, they don't work ok for a bit then not.


NT

[tabb...@gmail.com]

I'd probably start by prodding the pcb with a plastic stick, see if one spot is sensitive.


NT

[John-Del]

On Wednesday, September 19, 2018 at 4:33:13 PM UTC-4, tabb...@gmail.com wrote:
> On Wednesday, 19 September 2018 18:41:53 UTC+1, rodrigo...@gmail.com wrote:
>
> > I love old electronics and recently purchase a Panasonic TR-4CT5, it powers on and volume text is normally bright. Just have issues when I plug line in. Brightness of the input is fine for a minute then fades to super dark.
> >
> > Volume label stays at right brightness so I figured it;s not the CRT or brightness, feel it's a capacitor somewhere or something to do with the video input as on UHF noise is OK and doesn’t fade dark.
> >
> > I scoured google for a manual or service manual but I could not find anything.
> > Any help or guidance would be appreciated as I think it’s an electronic I really want to conserve.
> >
> > Thanks guys
>
> can't work out what you mean at several places.

I think he means that the only source that goes dark after a minute is the video input. The UHF snow and the on screen display maintain normal brightness at all times, so he correctly assumed the CRT as well as the HV and CRT circuitry are OK.

If it goes dark after running normally for a minute or so, I'd try cheating by applying freeze spray. Might turn up a gimpy IC or transistor in a couple of minutes.

If it's not thermally sensitive, I would check to see if the composite switching is done by a mechanical select switch or by logic control. A schematic would be a big help but on a b&w TV there's not much to them. If it's got ICs, that's half the battle as datasheets provide a partial schematic.