Sony KV25fs150 with retrace lines.

[SEAWOLF]

I have a Sony KV25fs150 which has retrace lines no video but there is sound.
When the television is switched on there are retrace lines with a bright screen
and then the television shuts down and the stand by light flashes 2 times.
The voltage supply which goes up to the CRT board is low and I have tested the
capacitor which is on that supply line and it is ok.I have also changed the video
amp IC on the CRT board .When I tested the supply which goes up to the CRT
board on the A board,it is very high before the television shuts down.

[Andrew F. Ali]

Re: Sony KV25fs150 with retrace lines.

Look for a problem in the Horiz Osc circuitry. Probably abad Non-polarized Hi-volt capacitor.

[tom66]

Re: Sony KV25fs150 with retrace lines.

I don't know a lot about CRTs but I did have this issue with a TV when the high voltage circuit was going too high - lack of feedback from the flyback or something open circuit somewhere?
I also saw it when I adjusted the SCREEN voltage too high (although it didn't shut down, the PSU just made a rather awful noise.)

[dick_barton]

Re: Sony KV25fs150 with retrace lines.

Personally I would say you line output IC is at fault. The frame output appears to be operating since it's attempting to give you a full height picture. Also as suggested check out your capacitors in the line output stage and any EHT HV caps.

Service manual
http://www.manualslib.com/manual/864...page=40#manual

[spicedrvr]

Re: Sony KV25fs150 with retrace lines.

Check the voltages at the CRT

R-K
B-K
G-K
G1
G2

Then pull the CRT Board away from the Tube, and then check the voltages again. Could be a shorted Tube.

Also, get a Sams and check the video drive voltages carefully.

[SEAWOLF]

Re: Sony KV25fs150 with retrace lines.

Look for a problem in the Horiz Osc circuitry. Probably abad Non-polarized Hi-volt capacitor.

Thanks for your reply.

[SEAWOLF]

Re: Sony KV25fs150 with retrace lines.

Check the voltages at the CRT

R-K
B-K
G-K
G1
G2

Then pull the CRT Board away from the Tube, and then check the voltages again. Could be a shorted Tube.

Also, get a Sams and check the video drive voltages carefully.

I have pulled the CRT board from the tube already and checked the voltages and it is not the tube.

[fredaelsadany]

Re: Sony KV25fs150 with retrace lines.

HI
you must measure 180 up to 200v that supplying the 3 cathodes through 3 resiistors (10 to 15 kohm/2w) . if this voltage is low the screen will be more bright with flyback (retrace lines) because the condinser of this voltage is dry .
it is about 10 to 22uf/250v.
replace it all will be OK .
THANKS

[R_J]

Re: Sony KV25fs150 with retrace lines.

On these sets its most likely the ic702, TDA6108 crt drive ic on the CA board (crt neck board), check check and see if it has +200 volts on pin 6, or check on l701 or c704 or c705. if its low its a good chance the ic is bad.
2 blink code os OCP on b+, If I do remember you can disconnect cn502 and see if the short goes away (you won't have picture with this plug disconnected) You can then isolate pin 6 of ic 702 if you like, or just remove the ic.
I bet its shorted internally

[Andrew F. Ali]

Re: Sony KV25fs150 with retrace lines.

Also too, a faulty Horiz Osc transistor may cause this issue.

[R_J]

Re: Sony KV25fs150 with retrace lines.

Also too, a faulty Horiz Osc transistor may cause this issue.

If there was no horz. osc. you would get no picture at all. The horz. drive signal comes from the y/c jungle ic not a single osc. transistor.
This should be the same manual

[SEAWOLF]

Re: Sony KV25fs150 with retrace lines.

On these sets its most likely the ic702, TDA6108 crt drive ic on the CA board (crt neck board), check check and see if it has +200 volts on pin 6, or check on l701 or c704 or c705. if its low its a good chance the ic is bad.
2 blink code os OCP on b+, If I do remember you can disconnect cn502 and see if the short goes away (you won't have picture with this plug disconnected) You can then isolate pin 6 of ic 702 if you like, or just remove the ic.
I bet its shorted internally

I have changed IC TDA6108 disconnected CN703 and checked all the voltages on the CRT board and they are low.I have checked the volts at the cathode of
D523 which is located on the A board and it is high.When I unsoldered the diode
the volts is 178v.Therefore it appears that there is a fault on the A BOARD.

[Andrew F. Ali]

Re: Sony KV25fs150 with retrace lines.

Check electrolytics in the Power Supply...maybe a faulty 470uF 25V

[fredaelsadany]

Re: Sony KV25fs150 with retrace lines.

hi
if KR/KG/KB are 180v you are raising the screen voltage plaese decrese the screen from line transformer (lower put) . if no effect change line transformer .
thanks

[Andrew F. Ali]

Re: Sony KV25fs150 with retrace lines.

I think fredaelsadany is saying the Flyback transformer, as the lower pot is the Screen control. Yes, she might be right...look also at the Big Filter Capacitor, too.

[SEAWOLF]

Re: Sony KV25fs150 with retrace lines.

I think fredaelsadany is saying the Flyback transformer, as the lower pot is the Screen control. Yes, she might be right...look also at the Big Filter Capacitor, too.

I have lowered the G2 control completely and the retrace lines are still present
and therefore I will continue to check for any faulty components on the A board.

[R_J]

Re: Sony KV25fs150 with retrace lines.

I have changed IC TDA6108 disconnected CN703 and checked all the voltages on the CRT board and they are low.I have checked the volts at the cathode of
D523 which is located on the A board and it is high.When I unsoldered the diode
the volts is 178v.Therefore it appears that there is a fault on the A BOARD.

You must be using a different service manual than me, do you get +200 on tp94?

[SEAWOLF]

Re: Sony KV25fs150 with retrace lines.

You must be using a different service manual than me, do you get +200 on tp94?

I am using the service manual for the Sony KV25fs150.

[Andrew F. Ali]

Re: Sony KV25fs150 with retrace lines.

If checks on the Horiz Osc and Output circuitry like Hi-volt Non-polar Caps, Horz Osc and Output Transistors. Main Filter Cap and other small electrolytics in the Power Supply are OK. I would check ALL the Hi-k resistors around the F/back Transformer then I would conclude that the fault is with the F/back Transformer.

[R_J]

Re: Sony KV25fs150 with retrace lines.

I did not have that exact diagram but I think I have it now, is this the same? if it is, when you disconnect cn703 from the cv board does the voltage +200 volts come back on D523 (K) on the "A" board, and does the error go away?