CRT Television Set Problem

[Rossua]

Hi I have 21" CRT television from the Stone Age, a Panasonic TC-21R1, about 19 years old, and recently the picture has started to shift to the left about 2-3 inches, and pin-cushion (ie bowing) on the right hand side.

When I hit the TV cabinet with my hand it goes back to normal, and the picture is perfect. But then after a few minutes the problem starts up again.

(The problem is the same whatever is connected up to it, eg VCR, cable TV box, DVD player etc)

I wonder what could be wrong and could it be easy to fix.

If just banging it puts the picture back maybe its a minor problem?

Thanks.

 

[OwainDIYer]

Dry solder joint.

The difficulty is finding which one.

 

[Rossua]

I have the tools - soldering iron & multimeter - and some basic knowledge, I'm gonna have a look now and see if there's anything obvious, else it'll be time for a new one I think.

About an hour ago it started making strange fizzing noises and picture went away completely, except for blurry vague colored 'cloud' in the middle of screen. Banging it brought picture back to perfect again, and noise went away, but it kept coming back again so I switched it off.

I put it on again later and for last 10 minutes or so its been working fine.

I repaired my digital piano recently, which had a sticking key, and saved on expensive repair charges, and I also repaired a portable cd player, all I did was remove and re plug in various connectors and it started working, so its worth a quick look.

 

[plugwash]

remember about the high voltages that may be present in the HV circuit even when switched off

 

[Rossua]

Yes thanks I am being careful not to touch anything by hand directly, only with electricians screwdriver, or multilmeter probes.

 

[wotan]

Yes thanks I am being careful not to touch anything by hand directly, only with electricians screwdriver, or multilmeter probes.

You could still receive a massive shock, a CRT tube is like a large capacitor it stores several thousand volts, take care.

Wotan

 

[joinerjohn]

I repaired my digital piano recently, which had a sticking key, and saved on expensive repair charges.

I replace the pitchbend potentiometer on my Yamaha keyboard at least once a year. Usually has to be replaced through wear. Why on earth Yamaha didn't go with an optical pitchbend unit I don't know. More reliable and hardly wear out.
First time I had one replaced, it cost me £25 at an authorised repairer, but the part itself only costs about £4 from Yamaha and takes about 10 minutes to replace.


Back to your original post,,,, Ahh the infamous "bang the tv routine." Used to have a TV like that some years ago till it got banged once too often. Mind you it did have valves inside it.

 

[Mickymoody]

Sounds like a 12V regulator is failing, thats the shift in picture, the bowing is it's supply capacitor is being overworked, and drained, so possibly has an oval top to it, 33v cap. In the picture delivery section, far far away from the Power Supply section.

Panasonic are reliable, but hard to fix. A websearch should tell you which components are broken, with a repair kit.

Had that exact fault in College, the TV was is the student uni, and every day I walked past it, saying one day I'll fix that! As it was up in the roof on a stand..and I wasn't asked. Then one day..it was on my bench. Quick fix.

If it's carried on being used..then the power supply will probably blow up.