I don't have the service manual copy. I was servicing these sets more than 6 years ago when I was working with a service contractor for warranty repairs.
The degausser is very simple. The AC is switched on with the relay. The relay feeds the degausser in series with the thermisistor. There is not very much involved to trace this out by following the traces on the circuit board.
The common fault is that the thermistor goes bad. You can order this part from any of the parts distributors for Sony parts. I cannot remember the cost of the thermosistor, but I think that from Sony it was in the area of about ten dollars at the time.
It is very rare that the coil or the relay goes bad. On some rare occasions I have seen cold solder connections cause the degausser to not function.
Your set will work with no degausser working. You can order from any place that sells parts for TV service, a manual degaussing coil that plugs in to the AC. You can manualy degausse the CRT face several times per week. This should work out well.
Manual CRT degausser coil:
http://www.datadev.com/degausser-small-office-monitor-tv-television-dc13.html
My preference is original parts. But, if you want to chance an after market part check the link below.
Donberg Electronics sells some types of thermistors:
http://www.donberg.ie/warehs/grouptp.htm
In the service shop we used a manual degausser when were changing picture tubes. We needed to have the screen degaused very fast so that we can do the purity and convergence set-up.
Jerry G.
These parts can fail. Very often the failure is not visual. This type of part is not able to be simply tested with an ohm meter. It is very current and voltage dependent to operate.
When you turn on the set, you should hear the degausser work. It makes a thud type of sound coming from around the metal shielding that is housing the CRT. If you look carefuly you can see the degausser coil sitting sort of below it. This coil is wrapped in high temperature type plastic tape. It should be connected through a pair of black and white wires to the power supply area where the thermosistor is located.
The replacement part is not difficult to order from any place that sells Sony service parts. As I said, it is not expensive.
If the degausser is working and there is discoloration in the picture, providing that the yoke and purity set-up was never disturbed, the mask inside of the tube, properly called an "apature grill" for the Trinitron tube may be warped or not sitting properly. In the regular CRT, this part is called the "shadow mask". This defect can happen if the set has been dropped or hit sort of hard. This part can easily be damaged. I have seen the apature grill be damaged while the set was being moved by movers, or simply moving it between rooms. It does not take much.
Also, if someone goes near the face of the CRT with a very strong magnet, they can pull it hard enough to do some damage.
Damage to the grill is not able to be repaired. This means a new CRT. Considering CRT's these days, new or rebuilt ones are very scarce to find. Their cost is also not worth it anyways.
Jerry G.
If you call an authorized Sony parts dealer, they can find out the correct part number from the model and serial number of the set. If you buy a 2 leg type and specify it for the Sony, I believe that all the Sony ones are very much the same, especialy in the same size range of set. Your set was a very common size.
As for putting a magnet near to the edge of the screen and making the fault look less, this tells me that the screen may be badly magetized and you are introducing a nutralizing effect. If you can have a gratting pattern to check the convergence, you may find that when you make the problem go away with the magnet, the convergence is getting offset.
What would be nice is if you can get your hands on a manual TV CRT degausser and see what happens. Maybe there is a local TV shop near to you where you can leave a deposit on one, and sort of make the man a rental deal, or simply pay him a service call to look at the set for you and degausse it while he is there. He may also be able to order the part for you and change it right in house. If he has a lot of experience he should be able to recognize if the mask in the CRT is bad, or it is simply a magnetism problem.
If the set was good before, then I would not say that it is a purity adjustment problem. It is either a magentism problem, or the mask is damaged.
Jerry G.
I have a supplier called Global Electronics Supplies. They are one of the biggest for TV service parts.
http://www.globalsemi.com/aboutus.aspx
Tel: 1-800-668-8776
If they cannot have the part, order yourself a hand held TV degaussing coil. You can manualy degausse the CRT a few times per week.
The other solution is to find a scrapper TV set with a good part in it. Most of these thermosistors are very much the same. If you took one from another manufacture in the 25 to 32 inch size it should also work for you. This is a very simple operation type thing.
Jerry G.
Getting back to this part, I do not have the service manual to know the part number. But, any authorized Sony parts dealer should be able to locate it through their system.
Jerry G.
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Thanks for that. I took the THP601 right off the board and re-installed it. It has 2 pins. Didn't solve the problem though. Still got the weird colors on the sides of the screen. Strangely, there are small area right up against the outside ofthe screen that seem to be unaffected. Very thin area of normal color. Centre of the screen is fine...normal. May not be a degaussing issue. Took the THP601 appart and it is pretty simple...just a PTC with contacts....nothing to break. Does the PTC loose is resistance? Just a ceramic disc.
Thanks again Jerry. The degausser does seem to come on and "try" to eliminate the color distortion. Starts to wave in and out.....but it stays, partially.
Oh well, thanks for the very excellent help.
Looks like a LCD is in my future.
one other quick note.......if I move a magnet near the sides the picture returns to normal. So I will order the THP601 and possibly the relay as well......worth a shot. Everybody talks aboutthe THP being 3 legged...as I said mine is 2 legged. Will the supplier know the correct one for the model. There is no part number on it.
Thanks again Jerry. I have tried to order the part THP601 from a couple of supply jouses and they both said it is no longer available. BooHoo..... : (
Do you know how I can get the correct Sony part number for this posistor for the KV27S42. I want to be sure to get the 2 leg one not the 3 leg one which is much more common.
I got the correct number...it has changed a couple of times. I'll let you know if that was the problem. Here's hop'n....Thanks for ALL the help.
Jerry...do you know what the resistance should be on that thermistor...THP601 ( original part # 180358611 changed upto 180354111) on the KV-27S42. I did order the part but they send me a 3 legged part, original was 2 legged. They said this was the replacement. It has 2 pieces of ceramic disc inside with a resistance on each of 9 ohms....total if I just connect the two pins of 18 ohms. Does that sound like the correct value? The old one was tested at less than 1 ohm....but it could be bad. Need to get a schematic to see what the value should be. Any idea where I can get that info? Thanks
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