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Old 2nd Sep 2007, 10:08 pm   #1
ballistic
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Smile Sony Trinitron

Hi guys

I saw a KV M2531U under a table at a car boot sale in Bournemouth. I bought it.
This one (KV M2531U) has a brilliant picture, no problems at all, very bright, but alas, just missing the nicam stereo and has 1 scart and no stereo outputs on the rear - but is 2 " larger and actually works fine!

QUESTIONS: How old is my new KV M2531U? Can't find it anywhere on the web.

Secondly, what shall I do with the old KVA2122U? I learnt a lot from it and it's the first tv I've poked about with; I did get rid of the flyback lines, but, alas, it seems determined to keep returning to this range of similar faults despite the help of those on here.
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Old 3rd Sep 2007, 7:25 am   #2
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Default Re: SONT Trinitrons

The KVA2122U and KVM2531U both use the AE1C chassis and were produced in 1991/2 (from the Sony chassis guide in Television July 1998). So neither of them are 'vintage' under the forum definition... Reasonably reliable sets apart from the usual dry joints and dodgy trimmer cap on the colour decoder crystal. Sometimes you get heater to cathode shorts in the tubes though, you are warned.

Dave
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Old 3rd Sep 2007, 10:50 pm   #3
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Default Re: SONY Trinitrons

BTW, it's a 25" set, not 23"

And there's nothing necessarily wrong with eBay TVs... I've bought 3 or 4 huge Panasonics from private sellers for peanuts and they've all been absolutely brilliant.

Nick.
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Old 3rd Sep 2007, 11:48 pm   #4
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Default Re: SONY Trinitrons

Hi dsergeant - thanks for the info - yes they both look of the same era - I thought they were similar.

Hi Nick - 25" then - I guess they slightly over estimated the screen sizes back then. Great news.


I diagnosed the problem with the KVA2122U myself and sent the IF circuit to a member on here who resoldered it for me. Things seemed fine for some months although the TV seems to play up when you get a change in the weather.

I've also noticed of late that a good thump seems to rectify any probs for a while.

I had been losing certain colours and, at its worst, the entire picture. That issue is still unresolved.
However the problem which I suspected was the IF circuit was where the inputs go mad, and start selecting channels and inputs on its own and making popping sounds as if turning the set on and off rapidly.

That second problem has slowly returned and is the one you can fix by thumping the TV.

By the way - if I sound like I don't know what I'm talking about - I don't. I've learnt a hell of a lot, but more than anything - respect to you guys. I'm looking for my first good simple book on electronic fault finding right now.

cheers

Brian
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Old 4th Sep 2007, 7:56 am   #5
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Default Re: SONY Trinitrons

Ah the dreaded Sony IF dry joints.... The AE1's suffered from that. Later sets through various generation put the IF circuit in a small can. Identical problem, dries on the two IF transformer pins. Repaired those loads of times. Sometimes you miss one of the pins and it comes back later with the same problem....

Your problem could be dry joints on the scart connectors - the field chip which is close to there also develops dries, caused by people putting stress on scart leads. If you are getting wrong colours it could be dries on the CRT pcb or one of the tube heaters intermittent. If all colour goes replace the colour crystal trimmer with an 18pF capacitor. Intermittent sound is dries on the sound output amps.

Dave
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Old 4th Sep 2007, 6:31 pm   #6
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Default Re: SONY Trinitrons

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Hi Nick - 25" then - I guess they slightly over estimated the screen sizes back then. Great news.
You can always tell the screen size from the model number with Sonys, e.g. a KV-2020UB is a 20" set, the KV-2704UB is a 27" one, the KVA2122U a 21" etc.

Last edited by Nickthedentist; 4th Sep 2007 at 6:37 pm.
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Old 4th Sep 2007, 6:32 pm   #7
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Default Re: SONY Trinitrons

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I diagnosed the problem with the KVA2122U myself and sent the IF circuit to a member on here who resoldered it for me. Things seemed fine for some months although the TV seems to play up when you get a change in the weather.
If you have dry joints in the IF section, the telly should still work perfectly via the SCART socket (e.g. when watching DVDs or Freeview).
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Old 4th Sep 2007, 6:34 pm   #8
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Default Re: SONY Trinitrons

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I had been losing certain colours and at it's worst the entire picture. That issue is still resolved.
As Dave suggests, invisible dry joints on the tube base panel often do this. Resolder ALL of them with plenty of fresh resin-cored solder (don't just apply an iron to the old solder). This only takes 15 mins or so.

Last edited by Mike Phelan; 23rd Sep 2008 at 4:56 pm. Reason: Changed 'loosing' to 'losing' to make sense.
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Old 4th Sep 2007, 6:36 pm   #9
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Default Re: SONY Trinitrons

Quote:
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By the way - if I sound like I don't know what I'm talking about - I don't. I've learnt a hell of a lot, but more than anything - respect to you guys. I'm looking for my first good simple book on electronic fault finding right now.
I've all I know about TVs from fiddling with scrap ones, talking to people here, and... back issues of Television magazine. Look out for some, especially the ones from the 1970s, 80s and 90s.
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Old 8th Sep 2007, 7:31 pm   #10
ballistic
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Default Re: SONY Trinitrons

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Originally Posted by Nickthedentist View Post
As Dave suggests, invisible dry joints on the tube base panel often do this. Resolder ALL of them with plenty of fresh resin-cored solder (don't just apply an iron to the old solder). This only takes 15 mins or so.
I resoldered the CRT "end" PCB just like you said, well at least the large connectors which go in a circle to the tube itself and the colours have all come back to life.

Now... could this have been linked in any way to the main problem which has not re-occurred yet since I did this fix... that problem was an irregular and intermittent fault which would occur only now and then, popping in speakers like power surge with complete loss of picture and input changing through the various scart inputs on its own, which sometimes could be resolved by hitting the top of the TV, or sometimes it was so bad, just had to switch it off and give up.
?

answers on a postcard please!
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Old 9th Sep 2007, 2:30 pm   #11
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Default Re: SONY Trinitrons

Most likely is dry joints on the 3-pin regulators - rework the soldering, also re-do the pins of the LOPT and chopper transformers, also the earthing straps.
Glyn
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Old 9th Sep 2007, 9:55 pm   #12
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Default Re: SONY Trinitrons

Hi Welsh Anorak,

Now I'm not sure where the 3 pin regulators are but if they are the 3 larg(ish) transistors on the CRT base PCB, it looks like they may have already been resoldered when I had a similar issue many years ago (the one other time I've had an engineer fix the TV),


I think I know what the LOPT transformer thingy is - the high voltage transformer with the lead that shoots off to the "suction cup" on the tube, which we don't touch.

Not sure about chopper transformer. Complete guess here, but is it the medium sized transformer on the main board fairly close to the LOPT?

Earthing straps, I have no idea, what do they earth and where are they?

I appreciate your help - thanks.


Hi Nick, that colour was perfect when it was working straight after the resoldering, but when I turned the TV on this morning, the other problem was back with a vengeance; to the point that the TV is hardly coming on at all now.
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Old 9th Sep 2007, 10:34 pm   #13
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Default Re: SONY Trinitrons

The way I rework AE1's versions B & C is s follows:

Remove the main board from the frame, remove the tuner IF module, resolder joints on IF transformers AND the edge connector. Inspect other joints under a magnifying glass and resolder as necessary.

Check/replace C531 & C532. C531 is a 680µF/50V capacitor: originally a 25V type was fitted, it is safe to use a 35V type but it must be 105 degree type. C532 is 100µF/50V again use 105 degree type.

Remove the old solder, clean the pins and resolder IC603 IC604 and any other three legged regulator IC's.

Do the same for the sound output IC's IC251 and IC261

Also the frame output IC IC500

Check/replace C615 1000µF/25V, can have 1500µF fitted.

Resolder all the video output transistors in CRT board.

Check/resolder joints on headphone socket

Check/resolder the joints on the edge connector of the J1 board which is mounted vertcally and at the back of the chassis, it carries the scart(s) sockets. Check for dries on both this board and the main board.

Methinks that's about it, there have been other less common problems but these are the main ones.

You won't find either the chopper or Line O/P transformers going dry jointed, this affected the earlier AE1 and AE1A chassis.

Good luck.
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Old 9th Sep 2007, 11:10 pm   #14
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Default Re: SONY Trinitrons

Hi
Well, I doubt I could have come up with a more comprehensive list than that! I have had the odd dry joint on the chopper Tx (yes, the medium sized one) especially if the set's been moved - it doesn't hurt to solder this. The capacitors mentioned will usually have a decidedly shrunken appearance. As with any Sony, a few minutes with a magnifying glass will pay dividends!
Glyn
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Old 30th Dec 2007, 8:58 pm   #15
ballistic
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Default Re: SONY Trinitrons

Hi, there's only so much I can reach on this Sony without taking the mainboard out.

It looks like it is designed to slide out on a tray.

Can you tell me if this is the case and if so, how you release the "tray" holding the mainboard?

Sorry in advance for what is probably the most basic question!!!
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Old 30th Dec 2007, 9:05 pm   #16
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Default Re: SONY Trinitrons

Not sure about your particular Sony, but you're right in that the main PCB might come out attached to a plastic tray assembly.

This often is just released by sliding backwards towards the rear of the set. Sometimes you have to bend a plastic "latch" or two out of the way first, or remove one or two screws (sometimes right at the front under the tube). USE A TORCH to see what's holding yours.

Nick.
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Old 30th Dec 2007, 9:21 pm   #17
ballistic
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Default Re: SONY Trinitrons

Ar, thankyou.. it appears that you "lift and pull" which releases some small plastic lugs pointing downwards. The whole board comes free including the front facia controls. The first thing which appears to prevent the board coming out all the way are white cables connected to a wire around the screen, which I guess are the earthing straps?
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Old 31st Dec 2007, 12:58 pm   #18
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Default Re: SONY Trinitrons

If this is a thick white cable running around the circumference of the tube, it'll be the degauss coil. This plugs into the board on all the sets I've worked on, so can easily be removed. There is sometimes a clip on the plug though which you need to carefully free before it will come out though. If all of the other connections to the tube base/anode/scan coils are still in place but have enough length to allow the chassis to be removed, just be careful not to over-stretch anything.
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Old 31st Dec 2007, 2:16 pm   #19
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Default Re: SONY Trinitrons

Well, I've put it all back together having resoldered the video output transistors on the CRT board, the earthing straps to the CRT and IF module (the IF circuit which has already been resoldered) and I still have no picture and just a pop when turning on, although the tube does seem to fire up because the tube flickers as it should do when turning the TV off, and it makes the customery sound a TV does when you turn it off.

I'm really disinclined to pull the whole board out and start resoldering the aforementioned capacitors and ICs on the main board, although I have managed to pinpoint some of them.
This is partly due to lack of confidence as I am discovering you need the care of a bomb disposal expert to carry out most of this work and I have come from a background of building PCs which needs the care of a 4-year old with a Lego set.

Just to recap the story, I resoldered the circle of pins which attach the CRT end cap to the CRT board and the TV fired up perfectly for a whole evening with really vibrant colour.... but the next time I tried to turn it on, it fails to work with just the pop as described above.

The only other nagging thought I have is... as the first adjustment I made was to turn down the screen voltage adjustment on the crt board to darken the screen, is it just possible that this needs turning back to where it was, now that we presumably have a normal voltage coming through the circuit?
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Old 31st Dec 2007, 2:28 pm   #20
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Default Re: SONY Trinitrons

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The only other nagging thought I have is... as the first adjustment I made was to turn down the scrn voltage adjustment on the crt board to darken the screen, is it just possible that this need turning back to where it was now that we presumably have a normal voltage coming through the circuit?
Just possibly! Some TVs do shut down if tube voltages/currents are wrong. Must be worth a go.

P.S. It's good practice to mark the position of presets before you adjust them, so that you can put them back to their original position if no improvement is gained
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