Sony Kp-44px3u

12240 Views 44 Replies 2 Participants Last post by mikelan, May 21, 2013

mikelan

Discussion Starter · Apr 19, 2013

Hi All,

First post on the forum, and asking for help as is usual.

I have a Sony Kp-44px3u rear projector TV that I don't want to send to the skip just yet. The LED blinks 3 times repeatedly which from the service manual indicates it has an OVP problem.
I have read several threads saying it's the STK392-560 convergence IC's etc and check fuses so that's what I have done.
Some probing on the G card showed 4 fuses blown. The +/-15v and the +/-19v picofuses specifically.
This seems to agree with the usual diagnosis of STK's blown so I have desoldered and removed them.
Also now I have replaced the 4 fuses that were blown but the two +/-15v ones are still blowing even though the STKs are removed.

If I replace the +/-15v fuses again and disconnect the connector to the D board they do not blow, indicating it is the D board that is blowing them.
Also with the D board connector (CN6009) disconnected I now get the LED flashing 8 times indicating horizontal protection, which may or may not be reasonable, I don't know.

So my questions :
1. Is there typically anything else on the D board that would cause the +/-15 picofuses to blow ?
2. Is it expected that the TV will work without the STK chips ?, I think it should just have a distorted picture ?
3. Any further advice ?

I don't mind spending time on this TV as it's a bit of fun to get these things working and any help is appreciated. I have the service manual and know my way around a schematic etc but not too familiar with TV systems but know enough what to touch and what not to touch ).

thanks !

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mikelan

Discussion Starter · #41 · May 9, 2013 (Edited)

If I cover the green lens it disappears completely so it must be something there, either CRT or lens.
It's hard to get a good look into it but I'll take off the lens again and try.

edit>> its definately there when I look down into the CRT with the lens off.

Does this mean the phosphor has been burnt off the centre of that CRT ?, bummer...

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lcaillo

· #42 · May 11, 2013

Probably a bad spot in the phosphor.

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mikelan

Discussion Starter · #43 · May 19, 2013

at last got my audio IC in the post. Soldered it in and now have sound.

Finally spent a bit of time trying to get the colours good and nearly gave up but came across white balance controls in the PJ engine settings.
For some reason all the WB settings were miles away from the default settings. I changed them all back to default and picture came good at last. I wonder did this cause ( or was the effect of ) the bad transistor in the red neck board ????

My last problem now is the convergence, or auto convergence rather.
BTW, I soldered in 2 new STK392-570s as I bought them way back when I thought the originals were gone.

Anyway using the coarse and fine adjustments in the PJ engine service menu, I can line everything up and save.
I get a terrific picture once I do this. After power off and on again the picture is still good so the settings were saved for sure.

However now if I press the auto convergence button, the white cross appears and it does it's stuff.
Once its finished the 3 colours are all wrong again. The auto convergence undid all the good and makes the picture worse.

Any ideas ?

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lcaillo

· #44 · May 19, 2013

You have to initialize the auto convergence. It really is just a reset to the last time it was stored, and the only adjustments it makes are static convergence and resetting to the dynamic convergence settings in memory. I don't recall the procedure. It is likely in the service or training manuals for that chassis series. You also have to store the convergence for each resolution, IIRC. It has been a few years since I repaired these.

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mikelan

Discussion Starter · #45 · May 21, 2013

You're right. After the calibration it must be saved. I missed that bit.
Redone it all again and now the auto-convergence works fine. Thanks for this.

I think I'm done now with this TV.
To summarize and for completion, here's the list of things that were wrong.

1. 19V Zener Diode shorted causing the 15v Rail to get pulled to gnd blowing all the relevant G Board fuses.
2. PNP Transistor on the Red neck assy board.
3. Audio Amp IC damaged
4. Replaced the STK IC's for good measure.
5. Full reset of white balance controls.
6. Cleaned and calibrated.

Attached is a picture of how it looks now. The photo doesn't show up how good it is in fact.
A HD channel coming through on the scart looks terrific and I would say is every bit as good as my 5yr old philips LCD Full HD.

Thanks for your help lcaillo. I got there in the end.

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Sony Kp-44px3u

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