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#1
03-29-2008, 03:29 AM
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Sony Tuner Rebuild
Hi guys!
I have a early 90's Sony KV27-EXR10 set with a flaky tuner. Simply loses the channel intermittently. Video and sound are both fine from the composite and S-Video connector, and I had been using an old VCR as a tuner to alleviate the problem. Anyway, I want to get the tuner running properly, so I've ripped the chassis apart and pulled out the tuner (Sony BTP-202, part #1-465-384-11). I see several places that 'rebuild' these for pretty cheap prices (as an aside, a 'rebuild' seems a dubious labeling, since there's not much more than a lot of small coils, surface-mount resistors and possibly caps and diodes, and two whole IC chips). I don't know who to trust...these old CRT units aren't worth squat, so I'm trying to keep it fairly cheap, but I still want it done right. Is there someplace that any of you trust to see that I get a good, functional, and trustworthy part back? Thanks!
__________________
In battle, in forest, at the precipice in the mountains, On the dark great sea, in the midst of javelins and arrows, In sleep, in confusion, in the depths of shame, The good deeds a man has done before defend him. --Bhagavad-Gita 
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#2
03-29-2008, 09:40 AM
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Chances are it's the IF module, not the tuner. It's usually caused by bad soldering on one of the coils near the IF IC.
Occasionally, I've seen bad soldering in the tuner, but that's much less common. I've usually been able to fix those tuners by reflowing the solder on some (or even most) of the connections in the tuner. Start with the ground connections, then do more if that doesn't take care of it. If you end up needing a tuner, I'm sure someone here can give you one. Sony only used a few types of tuners in that time period.
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#3
03-29-2008, 11:14 AM
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Quote:
Just to mention: If the symptom is that the tuning is drifting, that's the IF pack. If it's snowy or popping off to a blank snow screen, then the tuner has bad connections. Charles
__________________
Collecting & restoring TVs in Los Angeles since age 10
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#4
03-29-2008, 11:17 AM
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I'll second that advice on resoldering the coils inside the IF can. The IF can is a small metal can that is soldered on the chassis close to the tuner. You'll have to unsolder the IF can from the chassis and unsolder the shield on the IF can. Resolder all the coils and it should be fine. I've seen it many times on '80's and early '90's Sony sets.
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#5
03-29-2008, 04:33 PM
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Hmmm...well, I'll pull it out and give it a whirl. Thanks guys!
__________________
In battle, in forest, at the precipice in the mountains, On the dark great sea, in the midst of javelins and arrows, In sleep, in confusion, in the depths of shame, The good deeds a man has done before defend him. --Bhagavad-Gita
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#6
03-29-2008, 07:11 PM
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Resoldered most of the connections in the IF box...the coils, the IC, the transistors, and the blue-epoxy-encased mystery components. I did not resolder everything, as there's a lot of SMD components on there that I could see being easily lifted off.
Anyway, put the tuner and IF assembly back in, and buttoned at all back up. TV came to life for the first time in 3 years (  ), and so far (two hours) the channels all seem to lock in just fine. Before, I'd usualy have it on for about an hour and the channels would slowly drift away...going slowly from bright, clear pic to snow.Interesting that I really saw nothing wrong with the solder job that was already on the board...  I'm cautiously optimistic...
__________________
In battle, in forest, at the precipice in the mountains, On the dark great sea, in the midst of javelins and arrows, In sleep, in confusion, in the depths of shame, The good deeds a man has done before defend him. --Bhagavad-Gita
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#7
03-30-2008, 11:38 AM
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Glad it seems to have helped! And I didn't mention it, but I don't do the SMDs either. I don't think I've ever seen one of those being a bad connection.
It's 90% of the time the coils. Also, on that EXR series, there are several secondary 5-volt, 9-volt & 12-volt B+ supply regulators which are heatsink-mounted, and physically near the center of the board. They always have bad connections, but they don't particularly cause tuner-looking problems. Usually when those get bad connections, the result will be popping on & off, and sometimes a vertical collapse. There is a plastic support below the board, which virtually hides the connections. If you follow that support as it crosses the main frame holding the board, you will see 3 or 4 of those regulators' pins, and if you look through a magnifying glass, you'll see cracked, cold joints! But if it's fine now, leave well enough alone and just bear the regulator connections in mind for the future. Charles
__________________
Collecting & restoring TVs in Los Angeles since age 10
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