JP1 Remotes

The Robman · Posted: Tue Jun 12, 2007 6:44 pm Post subject: Sony Trinitron TV KV-20V80

So, I found this set on the curb earlier today, so I just had to pick it up to see what's wrong with it. Well, it appears that there's no picture (there is sound) and when you turn the unit off, there's two dots on the screen, one green and one red.

Anything I should check before I kick it back to the curb that might be easy to fix?
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zaphod7501 · Joined: 02 Aug 2004 Posts: 534 Location: Peoria Illinois

That's one of their "One-Chip" sets. A master processor controls every function in the set.

The most common general failure is a poorly soldered vertical output IC. Usually a 7 pin on a heat sink. TDAxxxx is the most common type. Tapping the heatsink might cause it to pop back in if this is the problem.

A weak picture tube can do it also. Turning up the G2 control can sometimes bring it out of blanking. The G2 is either on the high voltage transformer below the focus control or on the CRT socket board (use an insulated screwdriver).

Anything else is going to be really hard to fix.

edit: I checked here before I saw your email Very Happy

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Just call me Zaphod (or Steve) --- I never should have started using numbers in a screen name but I just can't stop now.

The Robman · Posted: Fri Jun 15, 2007 2:47 pm Post subject:

I found and re-soldered the "TDA" chip, but it didn't make a difference. So I looked for the control below the FOCUS control, which is labelled "Screen" and turned it. Turning this to maximum makes the screen turn purple (with lines across it). Does that give any clues as to what's really wrong?
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Please don't PM me with remote questions, post them in the forums so all the experts can help!

zaphod7501 · Joined: 02 Aug 2004 Posts: 534 Location: Peoria Illinois

That tells us that it has high voltage and filaments. The power supply is working and the micro is running and the CRT is probably OK.

It could be loss of vertical. Turning up the screen would cause the beam to bounce off of the inside of the tube, and produce brightness (but no video) on the screen. That's hard to tell for sure without seeing the lit screen.

It could be a failure anywhere in the video processing circuitry. (I assume you changed the video input to verify that it wasn't just a bum tuner).

Either way, it's scope and schematic time.

Sorry, but it may be back to the landfill time for this one, unless you want to start some serious troubleshooting. If you had a few chassis to borrow parts from it might be possible but I don't think we're in the "easy fix" category.
_________________
Just call me Zaphod (or Steve) --- I never should have started using numbers in a screen name but I just can't stop now.

The Robman · Posted: Fri Jun 15, 2007 8:06 pm Post subject:

thedogzeus · Joined: 24 Jul 2007 Posts: 9

Rob, have you dumped this yet, if not I might just be able to help you fix....

The Robman · Posted: Tue Jul 31, 2007 7:39 am Post subject:

Nah, this set went back to the curb. What would you have suggested to fix it, I'm curious.

I have another Sony TV with problems...
http://www.hifi-remote.com/forums/viewtopic.php?t=5111
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Rob
www.hifi-remote.com
Please don't PM me with remote questions, post them in the forums so all the experts can help!

thedogzeus · Joined: 24 Jul 2007 Posts: 9

Bummer, I reckon the other lads were pretty well on the mark with their diagnosis.

My money would have definitely been on the Vertical Output IC. IC541 on the main PCB (it's a TDA8172), worth about $5. If the fault was in the horizontal stage it wouldn't be coming out of standby, and if it was in the vertical sync stage it would have been shutting down after a few seconds.

No pix but sound OK 8 times out of 10 = V.OUT IC failure
Would have been worth a shot, but oh well.....maybe next time.

As for the 29", you still having audio problems? Has it got audio on AV/Monitor out?

The Robman · Posted: Thu Aug 02, 2007 8:47 pm Post subject:

The 29" doesn't have a video out, just an audio out.

The 29" works OK while it's just hooked up to a DVD player or something like that, but when I hook it up to the output from my FM modulator, the picture will eventually start to roll.

After I first got the set, I had it hooked up for several months and it worked fine, but then the trouble started. Steve tried helping me fix it and I even eventually took it to a TV shop, but the TV guy couldn't get it to start rolling again. Then 5 minutes after I bought it home and hooked it up again, it started rolling.
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Rob
www.hifi-remote.com
Please don't PM me with remote questions, post them in the forums so all the experts can help!

thedogzeus · Joined: 24 Jul 2007 Posts: 9

Leave it with me for a while....I'm on leave from work for a week or so due to birth of second bubby.

When I get back on deck I'l do a litle research for you and see what I can come up with.