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Sony KV-27TS27 No Picture    
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madmanmapper



Joined: 17 Sep 2007
Posts: 36
Location: Chicago, Il, USA

PostPosted: Sun Feb 08, 2015 9:00 pm    Post subject: Sony KV-27TS27 No Picture Reply with quote

Sony Trinitron 27"
Model KV-27TS27

Hi guys! I am happy to say that my Sony has been serving me well for EIGHT whole years since I garbage-picked it, and repaired it with advice from you fine people.

Unfortunately, the time has come once again to crack the beast open and poke around in its insides.

The other day, as the TV warmed up, the picture became black and white, and started scrolling vertically. Letting it cool down would eliminate the problem temporarily until it warmed up again. I bravely opened the behemoth of a TV, poked around, and found cracked solder joints on the rearward plug on the outter-most vertical board.

I sucked all the solder off the plug pins, and resoldered. Now, I freely admit that I'm not the best at this. I've burned my fair share of PCBs by resoldering them. So with this one, I was EXTRA careful not to overheat the board. With fresh solder applied, I assembled the TV, and viola, it worked. Beautifully, at that, best it's been in years.

Minutes later, the picture went black.

Fearing I underheated the solder, I pulled the board and redid it. Put it back, got a great picture for 5 minutes or so, and lost it. A couple of power cycles and it has gotten progressively worse. Now, I'd be lucky to get a picture for one second as the tube warms up. The same goes for both tuner and RCA inputs. The sound is still fine.

However, the menus, volume control, and channel number all display perfectly against the blank black background. So I'm guessing that the tube and whatever sends it the final image (I'm betting that board I fixed) are fine.

I have triple-checked my work. I see absolutely no signs of burned board or arcing, including when the TV is on. The only thing I haven't done is pull the main chassis board and look that over. Mostly because I don't really want to discharge the CRT. Will if I have to, though.

https://dl.dropboxusercontent.com/u/37540750/2015-02-08%2020.33.25.jpg

https://dl.dropboxusercontent.com/u/37540750/2015-02-08%2020.34.09.jpg

https://dl.dropboxusercontent.com/u/37540750/2015-02-08%2020.34.40.jpg

Thanks for any help!
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JTS1957



Joined: 21 Jan 2009
Posts: 2286
Location: Far, Far Away

PostPosted: Mon Feb 09, 2015 1:15 am    Post subject: Reply with quote

Check the solder joints on the mother board 'socket' where the plug of the B board you've already reworked plugs into.
madmanmapper



Joined: 17 Sep 2007
Posts: 36
Location: Chicago, Il, USA

PostPosted: Mon Feb 09, 2015 9:21 pm    Post subject: Reply with quote

Yes, I suppose I should. I also looked into discharging the CRT and from what I can tell, the zap is no worse than that of a car's ignition coil. Which I've been zapped by many times. So I already took care of that. I'll get the board out and get back to you.
madmanmapper



Joined: 17 Sep 2007
Posts: 36
Location: Chicago, Il, USA

PostPosted: Tue Feb 10, 2015 11:47 pm    Post subject: Reply with quote

Well I took the main board out. I feel kind of stupid being afraid of discharging the CRT.

I went through all of the main board with a fine tooth comb, and I found a few solder joints that were 'meh' but only one that appeared genuinely cracked (see first pic below). And even that one didn't appear to be cracked through, the back side of it looked intact. It wasn't part of the board plug, I think it was a rectifier or something, I didn't even bother to look on the other side lol. I resoldered that, and maybe 5 others that were just not quite right. I also found 5 or so fully cracked joints on some of the metal heat shields. I doubt those are used to conduct, but I resoldered them anyway because I was already at it.

So far my TV hasn't caught fire yet, and it's still working after 2 hours.

Cracked joint, very close to the plug on the outermost vertical board.
https://dl.dropboxusercontent.com/u/37540750/2015-02-10%2021.17.24.jpg

Underside of that plug on the main board.
https://dl.dropboxusercontent.com/u/37540750/2015-02-10%2021.23.35.jpg



Thanks again. With any luck, it'll be another 8 years before this set needs fixing again. Also: Glorious CRT master race.

PS - While working on the main board, I noticed someone else had clearly worked on it before. A handful of joints looked resoldered already.
JTS1957



Joined: 21 Jan 2009
Posts: 2286
Location: Far, Far Away

PostPosted: Wed Feb 11, 2015 12:56 am    Post subject: Reply with quote

ANY pin that even looks like it has a 'ring' developing between the foil and wire should be resoldered (reworked). Pin # 17 of the connector, for example.

The Comb filter (CM351) processes chroma and luminance separately. The pin (#7) you point out connects to the 9 Volt supply (but apparently it is not used by the filter). It does however connect to pin 3. It comes from IC352.
I'd rework all the pins of all items mentioned. No need to be fancy, just heat each joint until molten, add a small amount of fresh solder, remove iron and move onto the next one. Just don't make any connections where the designers of the item didn't intend there to be one.
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madmanmapper



Joined: 17 Sep 2007
Posts: 36
Location: Chicago, Il, USA

PostPosted: Wed Feb 11, 2015 11:44 pm    Post subject: Reply with quote

JTS1957 wrote:
Just don't make any connections where the designers of the item didn't intend there to be one.


You don't say.

Don't worry, I'm pretty sure I got all the pins you mentioned. Like I said, I reworked all the ones that looked 'meh.' :)
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