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Old 14th Sep 2019, 6:20 pm   #1
Pietro123
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Question Sony Trinitron colour distortion

Hello, I recently got a Sony Trinitron KV-X25TA and it works just fine except one thing: there's some colour distortion. It doesn't make any difference if I turn it on and off, even a few times. I've heard it could be permanent damage to the aperture grille and trying to fix it with a degausser will just make it worse, but I also saw a video of a guy using a degausser on a Sony TV (and it worked) so I'm confused on what I should do…
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Old 14th Sep 2019, 6:29 pm   #2
barrymagrec
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Default Re: Sony Trinitron colour distortion

It should automatically degauss on switch on so check that the circuit is working.You do need to be careful using a hand degausser on a trinitron tube as the wires are very fragile.

I have seen trinitron monitors with that type of colour distortion after they had been dropped and it was unfixable.
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Old 14th Sep 2019, 6:32 pm   #3
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Default Re: Sony Trinitron colour distortion

Check the auto degaussing circuit, it could be faulty, I don’t have a circuit to suggest components.

Crossed post.
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Old 14th Sep 2019, 10:23 pm   #4
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Default Re: Sony Trinitron colour distortion

Does it make a loud BOINGGGGGGGGGGGGGGG sound when switching on cold?

Using an external degausser on a Trinitron should generally be okay, but should never be necessary if the internal degaussing is working correctly.
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Old 14th Sep 2019, 10:39 pm   #5
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Default Re: Sony Trinitron colour distortion

If it is a domestic set it will most likely have a 3-terminal thermistor that can be replaced with one out of another TV chassis.
They were as cheap as chips and contained one NTC and another PTC one.
They often rattle if they are faulty.
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Old 14th Sep 2019, 11:46 pm   #6
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Default Re: Sony Trinitron colour distortion

About two weeks ago I repaired an AE2B chassis (1993/4) which had psychedelic colour and no characteristic 'twang' at switch on. The degauss circuit was not activating despite the supply voltage and PTC being OK. I traced it to two leaky capacitors, which had corroded nearby resistors and a smd transistor, and the fusible resistor in the supply to the circuit had gone o/c. Unfortunately the details are on my other PC but I can check next week if necessary.

I think your set uses the late 1980s AE1 chassis, but it may use a similar timed degauss setup. If it has one of the large TDK manufacture degauss posistors, check its condition, the soldering, and replace if necessary with same rating.

Another cause of this problem is the rubber wedges below the yoke slipping off the tube, allowing the yoke to droop. Purity errors then result. Have a close look in the area inside the set to see if this is the case.
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Old 15th Sep 2019, 2:12 am   #7
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Default Re: Sony Trinitron colour distortion

This may sound silly but are there any large speakers near the TV?

My first Trinitron TV was badly affected by a magnetic field from a nearby, large pair of KEF Hi-Fi speakers.
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Old 15th Sep 2019, 6:54 am   #8
Pietro123
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Default Re: Sony Trinitron colour distortion

Quote:
Originally Posted by Maarten View Post
Does it make a loud BOINGGGGGGGGGGGGGGG sound when switching on cold?

Using an external degausser on a Trinitron should generally be okay, but should never be necessary if the internal degaussing is working correctly.
Yes, it makes that sound. If I just turn it off and on nothing happens, but if I wait for some time before I turn it on again, it does.
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Old 15th Sep 2019, 7:30 am   #9
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Default Re: Sony Trinitron colour distortion

Quote:
Originally Posted by camtechman View Post
This may sound silly but are there any large speakers near the TV?

My first Trinitron TV was badly affected by a magnetic field from a nearby, large pair of KEF Hi-Fi speakers.
No, I never keep speakers near my TVs.
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Old 15th Sep 2019, 10:49 am   #10
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Default Re: Sony Trinitron colour distortion

Quote:
Originally Posted by Pietro123 View Post
Quote:
Originally Posted by Maarten View Post
Does it make a loud BOINGGGGGGGGGGGGGGG sound when switching on cold?

Using an external degausser on a Trinitron should generally be okay, but should never be necessary if the internal degaussing is working correctly.
Yes, it makes that sound. If I just turn it off and on nothing happens, but if I wait for some time before I turn it on again, it does.
In that case, the degauss control circuit is likely fine. Just check the rubber wedes and also the pins of the PTC mentioned earlier.
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Old 15th Sep 2019, 7:38 pm   #11
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Default Re: Sony Trinitron colour distortion

The SONY AE2B service manual is available FOC and includes beam landing and convergence instructions which are the same for all late Trinitrons.

The instructions include placing small disk magnets on the CRT cone to correct beam landing errors which are usually quite difficult to remove but there is always a possibility that one or more could come off.

Nevertheless, the manual is must and then it is straight forward to follow using a static image.

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Old 15th Sep 2019, 8:35 pm   #12
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Default Re: Sony Trinitron colour distortion

My first thought was has the deflection yoke slipped down the neck, it's definitely worth a look. They can slip and yet still be super tight on examination. Sometimes you have to loosen it off first and ensure it is totally free before then really firmly pushing it up the CRT neck.
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Old 15th Sep 2019, 9:21 pm   #13
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Default Re: Sony Trinitron colour distortion

I agree with Mooly, instead of clamping the scan coils directly to the glass neck Sony clamped on to a piece of adhesive tape around it. Due to the force of the rubber wedges between the scan coils and the tube flare and because of the adhesive used the tape would creep back along the neck over time. The coils being no longer pushed up against the flare resulted in many sets showing terrible purity, convergence and/or raster correction.

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Old 16th Sep 2019, 9:21 am   #14
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Default Re: Sony Trinitron colour distortion

The yoke on a sony trinitron is adjusted for beam landing and requires the yoke to be placed in the correct position prior to static convergence. After which, rubber wedges are used to hold the yoke there. It is to SONY's credit that they use adhesive tape to provide a secure hold for the yoke clamp to remain in position when sets are shipped.

The yoke must not be pushed up against the flair but adjusted in a particular way prior to static convergence. The horizontal and vertical tilt required is then held in position with self adhesive rubber wedges which are not forced in place, which would cause an error, but to hold the tilt. The yoke should be tight against those wedges.

Without a photo of the yoke and CRT generally, it is difficult to advise what might have gone wrong.

Notwithstanding the possible reasons given why the set displays poor purity at the edge and corner, I recommend that should you wish to set up the CRT, only the procedure shown in the manual is followed. Trial and error will not work.

Chris

Last edited by simpsons; 16th Sep 2019 at 9:39 am. Reason: more detail
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Old 16th Sep 2019, 10:34 am   #15
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Default Re: Sony Trinitron colour distortion

Often no need to set it up fully if the yoke has sagged a bit. Just unscrew and push it up carefully.

Alle tube systems are adjusted for beam landing this way, not only Trinitron.
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Old 16th Sep 2019, 12:12 pm   #16
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Default Re: Sony Trinitron colour distortion

When you say you 'got' this set, was it sent by courier by any chance? If so it's probably had a good thump, in which case I'm afraid the shadowmask might have shifted, which is irreversible.
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Old 16th Sep 2019, 4:53 pm   #17
Maarten
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Default Re: Sony Trinitron colour distortion

Sony tubes don't have a shadow mask, but a heavy steel construction with tensioned wires in between, acting as a slot mask (aperture grille). It likely won't shift without breaking the glass, but it might bend. However given the symetrical nature of the fault, I don't think that's the case here.
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Old 19th Sep 2019, 12:10 pm   #18
Welsh Anorak
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Default Re: Sony Trinitron colour distortion

I thought someone would pull me up on that!
I have had a Sony with that display after a fall so it is possible, but obviously I'd rule out all the other suggestions first.
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Old 19th Sep 2019, 4:25 pm   #19
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Default Re: Sony Trinitron colour distortion

looking at the display, there are no static convergence errors. This suggests either magnetism of the grill which cannot be degaussed or the degaussing circuit isn't working properly.

Turning the set about its axis viz east/west rather than north/south might give some clues alternatively, just use some bar magnets on the CRT to compensate for purity error. As said earlier, use a single colour background to keep it simple.

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Old 19th Sep 2019, 6:19 pm   #20
Pietro123
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Default Re: Sony Trinitron colour distortion

Quote:
Originally Posted by Welsh Anorak View Post
When you say you 'got' this set, was it sent by courier by any chance? If so it's probably had a good thump, in which case I'm afraid the shadowmask might have shifted, which is irreversible.
No, I bought it at a thrift store, though when I arrived home and opened the hatchback the TV tilted and slammed. Fortunately I placed some cardboard sheets there and I don't think it was damaged in any way.
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