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Help me to solve this Complex Falult of Sony Trinitron Crt Tv

Ech

Feb 16, 2021
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I got an old Sony Trinitron Crt tv and decided to repair it. Firstly, when it is powered, the standby light turns on and after triggering the power button, the standby light turns off and within few seconds it comes back again to standby mode.(the standby light turns on again). B+ voltage = 115V and 15V output from the chopper transformer. I found that the 33v zenor diode is defective and repalced it. Also, all the suspicious capacitors including mylar capacitors are replaced. I found that the high frequency diode at H- Out transistor is short and replaced it. Then I powered the Tv and suddenly i heard high voltages at flyback are turned on and in a few seconds tv turns off and again turned on automatically with a sound of turning on high voltages of flyback transformer and again turns off. This happened repeatedly and i turned off the tv. Then i checked the new diode i replaced at H-out and i found that that diode is short as the old one was. I tried with few diodes but all of them became defective when i try to turn on the tv.
  • H-out transistor is OK.
  • I replaced flyback transformer but the problem is the same.
Could you please help to to solve this problem?
 

Martaine2005

May 12, 2015
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From experience, all Sony TVs had a known issue with dry/cracked solder joints. It was the number 1 go to for techs.
Based on that, I’d check or just reflow the board.

Martin
 
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Ech

Feb 16, 2021
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From experience, all Sony TVs had a known issue with dry/cracked solder joints. It was the number 1 go to for techs.
Based on that, I’d check or just reflow the board.

Martin
Thank you very much for the reply. As you said there were lot of dry joints and I observed them and repaired carefully. But the problem exists as it was. I don't know the reason for damaging the diode at the collecter pin of the H-out.
 

73's de Edd

Aug 21, 2015
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"old Sony Trinitron Crt tv"
No
way, that I / others can work, with JUST that meager info .
But you CAN initially come back with the exact info on the ( HV Damper) diode that you tried replacing and the specifity of the one(s) that you tried using.
 
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Ech

Feb 16, 2021
6
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"old Sony Trinitron Crt tv"
No
way, that I / others can work, with JUST that meager info .
But you CAN initially come back with the exact info on the ( HV Damper) diode that you tried replacing and the specifity of the one(s) that you tried using.
Thank you very much for the reply. The original and the shorted diode i found was "c06-15" (part number). I replaced it with a new diode with the same part number. The datasheet shows that it can handle voltages from 1300V to 1500V with 1.5A. I replaced three new diodes (same diodes) but when i try to turn on tv all of them became defective (short). Also, the H-out transistor (D1651) gets too hot but still it is fine.
 

Ech

Feb 16, 2021
6
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"old Sony Trinitron Crt tv"
Model number KV ??????
Thank you very much for the reply.
Model Number - KV-G21B1
and I found the following details on the chasis.
SCC-J40B-A
CHA.NO. 1004256
 
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