SONY CRT KV-32XBR15 No picture, sound OK

Thread Starter

groanzone

Joined Jan 30, 2022
6
Hello folks, I will preface this by saying I'm a beginner with electronic components but I do have a digital and analogue multimeter and know how to use them.

I've had this SONY KV-32XBR15 for 8 months and it's been working great until one day while playing a game the display just blinked off and I smelled a slight burning. Looking inside I found resistor R519 burnt up. Replacing the resistor results in it burning up again so obviously another component is causing this.

I have no picture (no OSD either), sound is okay, I can change inputs (since I can hear the sound from what I have in the inupts), the set still degausses, I feel static on the screen (paper also sticks), I have three glowing lights at the neck (not sure how bright they should glow, they're kind of dim), and I have no raster (the G2 adjustment on the neck board does nothing and the focus knob on the flyback has no effect).

Things I have removed and checked with the multimeter...
Transistors: Q502, Q503 (horizontal output transistor), Q504, Q505. All seem to test GOOD.
Diodes: D512 (damper diode), D501, D502, D511, D503, D505. Test GOOD.
Capacitors: C516, C517, C518, C519, C521, C522, C523. Test GOOD. C535 tests good but has a slight bulge on the bottom so I'm replacing.
Resistors: R519 BAD. R530, R533, R534, R542 GOOD.

I have not checked voltages yet. I'm thinking maybe the flyback transformer has failed but I haven't seen any cracks in the case and no arcing. I'm aware it can fail without these signs though.

If anyone could suggest some areas/components/voltages to check that would be much appreciated.

I am including the only service manual on this model I've been able to find.

Thank you to whoever can provide some assistance!

EDIT: I am also including the service manual for KV-27HSR10 which seems to have the same chassis/boards, but some component values differ.
https://www.dropbox.com/s/pilfzt303yxo21a/XBR Chassis.pdf?dl=0
 

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abrsvc

Joined Jun 16, 2018
117
My first guess would be to check the vertical IC TDA8172. This is likely to be shorted. The fact that you feel the static on the screen indicates the presence of HV and thus the HOT is working properly.
 

Thread Starter

groanzone

Joined Jan 30, 2022
6
My first guess would be to check the vertical IC TDA8172. This is likely to be shorted. The fact that you feel the static on the screen indicates the presence of HV and thus the HOT is working properly.
Thanks for the tip! I haven't checked an IC for a short before can I do that in circuit?
 

abrsvc

Joined Jun 16, 2018
117
I wouldn't try. But if you look at the schematic, the vertical IC is what is connected to the resistor that is burning. It suggests excessive current draw which is likely a shorted IC.
 

Thread Starter

groanzone

Joined Jan 30, 2022
6
I wouldn't try. But if you look at the schematic, the vertical IC is what is connected to the resistor that is burning. It suggests excessive current draw which is likely a shorted IC.
Just an update: I replaced the vertical IC TDA8172 and the resistor. The resistor blew again and still no picture.

Back to the drawing board! Thanks for the suggestion though.
 

Dodgydave

Joined Jun 22, 2012
10,361
What is the voltage supply on the vertical chip, also what happens if you remove the vertical scan coils with the chip fixed, how much current is the vertical timebase taking?
 

Thread Starter

groanzone

Joined Jan 30, 2022
6
What is the voltage supply on the vertical chip, also what happens if you remove the vertical scan coils with the chip fixed, how much current is the vertical timebase taking?
Hi Dodgydave, I'm sorry I'm a bit of a beginner with this stuff...

1. How do I check the voltage supply on the chip? Multimeter negative probe on a ground and positive on one of the pins?
2. How do I remove the vertical scan coils? Do you mean the deflection coils on the yoke?
3. How do I check the current of the vertical timebase?

Thanks so much for any help you can provide!
 

Thread Starter

groanzone

Joined Jan 30, 2022
6
UPDATE: in case anyone else comes across this issue. The culprit was D505 a 1000V rectifier diode, located right next to the resistor that kept burning up.

I noticed a black mark underneath the diode but failed to realize the diode itself was damaged on its underside. Oddly enough it tested fine in diode mode on the multi meter.

Thank you to everyone for your suggestions!
 
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