Samsung PS-42D4S plasma. Has sound, no picture. Please help!

[Maklaud]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

Here..

[scokljat]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

Here..

When TV is ON:

Vs = 6.5V (measured at Y-Sus/Z-Sus connector relative to chasis ground, no change when Sus boards are disconnected)

Take a look at beginning of thread.

Do you want me to measure Vs relative to GND_H? Probably not...

Thanks,

S

[ReeceyBurger123]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

Have you tried what I said or are you going to ignore what I put ???

[scokljat]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

Have you tried what I said or are you going to ignore what I put ???

I'm in a shop now buying these poly caps :-) stay tuned...


Update: bought the caps! These two caps are one of my primary suspects from the beginning. Definitely if these caps are bad, Vs will fail as on my TV set. They are located between heatsink and transformers, probably subjected to lot of heat. I'll replace them as soon as I get home tonight. Hope it will solve the problem...

Thanks!

S

[ReeceyBurger123]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

Great stuff keep us update hopefully they are the issue. Sorry for being snappy just wanted to know haha.

[scokljat]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

Unfortunately, no luck :-( I replaced both caps C523 & C524. Actually I tested old caps as soon as I took them out from PCB. Both tested good on ESR tester. Replaced with new ones just in case...

So, we are back to square one... Any ideas? What about ML4824? I really need to fix this TV...

Cheers,

Suad

[Maklaud]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

Do you have an Oscilloscope?
IC1 ML4824 (12 pin) Measure output signal.

[scokljat]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

Do you have an Oscilloscope?
IC1 ML4824 (12 pin) Measure output signal.

Yes I have an oscilloscope at my work. I'll take it home tomorrow. I'll measure pin 12 relative to pin 10. Right?

Thanks.

S

[Maklaud]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

At voltage VS is not there a short circuit?

[scokljat]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

At voltage VS is not there a short circuit?

Sorry, I don't understand what exactly do you mean?

[ReeceyBurger123]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

I think he means do the Pfc fets test ok ? Bad luck about the polly caps as well time to keep testing !!

[Maklaud]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

contact closure VS on RTN.
Did you not understand?

[Maklaud]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

Yes..measure pin 12 relative to pin 10.

[Maklaud]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

Try to remove the fuse (F4S) and turn on TV. VS voltage = ?

[ReeceyBurger123]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

Is the Vs on signal that the Mainboard generates present ?

[scokljat]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

At voltage VS is not there a short circuit?

Short circuit test:

VS to RTN (chasis ground) - OK, open
Q1 Q2 Q3 Q4 Q6 Q8 - no shorts
D9 D10 - no shorts
F20S - OK

So, this is only simple short circuit test with DMM. If I want to test all FETs and transistors in detail I'll have to remove them from circuit which is very complicated on this PSU...


Removing F4S sounds like good idea. Will try later... but, it anything important is shorted, I suppose some fuses would blow.

Thanks,

S

[scokljat]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

Is the Vs on signal that the Mainboard generates present ?

When TV is in standby VS-ON signal is 0.4V
When TV is switched ON VS-ON signal is 2.95V

When TV is in standby PS-ON signal is 3.3V
When TV is switched ON PS-ON signal is 0.25V

I measured VS-ON and PS-ON relative to RTN (chasis ground)


Thanks,

S

[scokljat]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

Try to remove the fuse (F4S) and turn on TV. VS voltage = ?

Tried to remove fuse F4S. With F4S removed I get Vs = 0.8V. With F4S installed Vs = 6V. (measured with Sus boards disconnected)

Normal Vs value for this PSU and plasma module is 175V.

Thanks,

S

[Maklaud]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

Try to change ML4824

[scokljat]

Re: Samsung PS-42D4S plasma. Has sound, no picture. Please help!

Try to change ML4824

I just bought ML4824CP1. It's a CP version which has slightly lower operating temperature range than IP version Samsung original. CP version has 0 to 70C and IP has -40 to 85C. IP version would be better because IC is located between two heatsinks, but CP is all they had in local shop for 6$. I'll try later, if it works I'll put a small heatsink on it. Stay tuned...

Thanks,

S