TV Doesn't Turn Off
 

My BPC '94 Panasonic has a strange issue. Pressing the power button on the remote or the set will usually cause the set to turn off. Other times it will click and the sound will turn off, but the picture will stay on. Pressing the power button again will cause another click and the image to fade in and out slightly, and the sound returns. Repeating this multiple times will eventually turn the set off.

This problem first surfaced back in '04 or '05, but a shop repaired it. Today I tried to turn off the set and it's back.

Is this fixable?

Thank you all.

Sounds like a sticky power relay to me. Next time it doesn't turn off tap the relay with a stick. It will probably turn off. If you don't have the TV open, you could try hitting the set with your hand, or pick up a corner and drop it an inch or so onto the table. Same deal....if that makes it turn off, replace the relay.

I have a similar problem with my SONY tuner.... Didnt start until I took her off where she is and put her on her side!!! -- Now the relay keeps going off (audio dissapears) and I have to tap the unit to get it back on :( (Started a few months ago)

Good luck to you Outland!! :)

Thank you Dude111.

Geoff, if it is a bad power relay, I assume new parts are unobtanium. Can a relay be cleaned? I couldn't find much information about this online.

I couldn't do the tap test today because it worked just fine. Go figure. When the problem first surfaced, it too happened rarely, then more often until it wouldn't turn off at all anymore, so I guess I have some time.

You should be able to substitute with another off the shelf relay if necessary.

Your welcome :)

I discovered what the problem was in my Sony...... One of the relay controllers for SPEAKER B was indeed loose on the board!! (I only use B) -- I took a rubber band and put it around both units in there (A/B) and it seems to be working fine...... (I did order another sony though as this one is almost on its last legs and I dont wanna lose this model,I love it! -- STR DE-185

I've done it before. As long as the housing isn't sealed, you can pop it off and clean the contacts (or even bend them a little if they're not springy enough). But after I did so, the relay had to be cleaned again not more than a year later, and it was harder to get back into shape the second time around.

My sony is still having issues..... Even with the control rubber banded down on the board she still goes into protect mode,etc........ I did order another DE-185 the other day...... Its really sad...... I DONT KNOW HOW THE CONTROL GOT LOOSE IN THE FIRST PLACE!!

I didnt slam it down on its side!!!! -- I was very gental (I was cleaning where she sits)

Maybe the heat from it being on so long loosend it? (With the vents covered maybe (I have my tape deck on top of it (The only air vents that get let air in are on the side)))


I hope thats not it but could be.........

Air vents are there for a reason. May not be your issue, but don't block them.

I agree that it's probably a stuck relay. You may not be able to get an exact replacement; but, you should be able to find something with the same coil voltage and contact arrangement. The placement of the terminals on the replacement may be different and you may have to get creative with mounting it; but, I don't see a bad relay as being something that will send this set to the dump.

I have an STR-DE545 and after a few years of use the speakers started cutting out. Just resoldering all the relay terminals fixed it and I have had no issues in something like 10 years since resoldering. (I bought it 16 years ago!) I would not be surprised if those joints were cold from the factory and a few years of normal use broke them. You should try that too.

The set hasn't had issues since, so I haven't been able to do the tap test. When the time comes, I'll just put in a new relay, the old one seems tired.

It happened again, and I recorded a video. Tapping the side didn't do anything. It turned off eventually after 10-15 tries. Is it a power relay?

https://youtu.be/ke62Pw5Leck

Might be easiest to just unplug it when you wanna turn it off until we can figure out whats going on with the switch......

Relay might be magnetized. The coil works on DC, so it can pick up residual magnetism.
Maybe you can get a tape head demagnetizer and pass it over the relay or make a home made demagnetizer out of a bolt and several turns of wire, connected to a 6 volt transformer. You need AC to do a good job of demagnetizing. :scratch2:

Thanks all, I'll try to demagnetize the relay.

Sticking relays were kinda common. Also a good spot for cold joints.
You can double check it by measuring the DC where the relay coil connects
to the relay driver transistor. Just follow the trace to find it.
When on relay coil will be source, usually 12 VDC on one pin & very low
on the other.
When off both will be the same.

Relay driver transistor will be when on
C = very low VDC
B = .7 > VDC
E = 0 VDC
When off
C - source, usually 12 VDC
B = 0 VDC
E = 0 VDC

Last the diode across the coil everyone wants to know about.
Without the diode when you turn off the set the coil field collapses
& the relay will chatter as it re energizes itself. The diode will short it out
& prevent chatter.

73 Zeno:smoke:
LFOD !

IIRC those diodes also absorb inductive voltage spikes caused by the field collapsing...ISTR that those spikes can fry lower voltage switching transistors if not suppressed by a diode.

It happened again. The set goes ‘click’ and the menu stops working then when I press the power button again it goes ‘clack’ and comes back as if the set has just turned on. For the time being, can I turn off the set by pulling the plug after the first click?

Can turning the set off like this damage anything? From what I understand, everything except the tube turns off with the first ‘click,’ as seen in the video, so turning off the set like this is ok?

https://youtu.be/ke62Pw5Leck

I was also wondering why there is still a click sound if the relay is broken? The sound turns off also.

Most sets if the relay sticks when you turn off most of the
micro is turned off & is only waiting for another ON command.
Therefor no channels, OSD etc.

Other possibility is the relay is only a degauss relay & ON/OFF
is done another way. Usually by turning ON/OFF the horz osc.

Best test is a new relay. Any with the same coil voltage from almost
any TV will work. You may have to extend terminals with wire.
Some sets are even drilled to fit 3 different styles......

73 Zeno:smoke:
LFOD !

Sounds good! I'll update this thread as I progress.

Here's the power supply schematic. Looks like there's only one relay, part #TSE1864 which is no longer available. So the replacement relay only needs to match coil voltage? Looks like the relay is also controlled by IC001 in the event of overvoltage.

https://20fsug.by3301.livefilestore....&cropmode=none

The replacement is TSEH8007 which is carried in some places. Next step is to change out the relay.

Sounds good.
Its a nice simple PS to work on. T001 / D001 are the STBY a.k.a always on
for the micro, relay & remote receiver ( source 2-3-4 & 5 ). Of note
is D022 puts a flyback derived voltage on it & takes over after start up.

73 Zeno
LFOD !

Other important relay specs contact voltage/current rating number of throws and poles in the contacts. A SPST won't replace a DPDT relay. Too little contact voltage or current rating could mean contacts burning up, arcing shorting etc.

Aside from that mechanical mount specs can matter...Though usually can be worked around and are less significant than coil and contact specs.

I picked up a very similar set (CT-20G11U) for free the other day, and will take the relay from that one if this one starts misbehaving again.

I noticed that according to encompass parts, the model I picked up and the TV in question (CT-20S2S) share the same CRT. The CRT in mine is getting tired and has a little CC burn-in (for proper black level brightness has to be boosted to 25% above factory), while in the model I picked up calibration is good at factory on the same tube. In fact, the tube in the new one is in excellent condition. Does this mean I can swap the tube from the new one into mine? What would such an operation entail?

If the yoke is the same super easy. 4 bolts, 4 connectors &
maybe a few wire ties. In my prime I could do it & have the
back on in <15 mn. Thats if none of the tools are hiding !
If you you need to swap the yoke you have to do the complete
CRT set-up. First one takes a while especially on in line jugs.

73 Zeno:smoke:
LFOD !

In my case, the yokes appear to be identical. I look forward to swapping them because the CRT in mine is certainly starting to get tired (though still outputs a very acceptable picture, Panasonic surely made excellent quality).

The one I picked up for free appears to have been dropped because there is some broken plastic on the top and the coaxial connector is partially broken off. Perhaps for this reason, the TV wasn't used much because the picture looks brand new.

Before I swap the relays, I think they should be identical even though they have different part numbers. Here's the power supply circuit from the donor TV.

https://1ke7ga.by3301.livefilestore....&cropmode=none

Apologies for the huge images. Are they the same as the relay from the circuit in the target?