60pb660v flogging a dead tv-shop visit req

[thuss]

Hi one last effort before this tv goes to a shop or the bin.

symptoms no picture only sound.

all the voltages are there apart from zbias which is 70v and the 18v rail which is only 4v. No green flashing light on logic board but logic board has been replaced 5v going to logic board.

Vy is 0v. resistors diodes are fine .

My mate who does all the diagnosing and soldering has given up.

In the attached photo he has checked everything in a yellow box and replaced everything in a double yellow box.

Main board is fine auto gen on logic board was connected -no test patterns generated.

Any pointers would be really be appreciated.

Thanks in advance Sorry about the repetitive postings.

[R_J]

Re: 60pb660v flogging a dead tv-shop visit req

Check pin 2 of P100 [CTRL_EN] I suspect it should be close to 5 volts to enable the control board. Q304 appears to be the VS_ON control pin I suspect it tells the control board that the VS voltage is ON and present on the ysus.
IC200 and Q202 are the smps for the 18v. If that circuit is running, 18v comes from D203 but due to protection circuits, IC200 may be turned off.
I don't know what ic200 is post it's number.
Is R206 ok? does it have Vs on both sides?
Also check R329, R330, R331, they connect ZD304 and then to Q304 base, Q803 collector connects to the VS_ON that goes to the ctrl board

[thuss]

Re: 60pb660v flogging a dead tv-shop visit req

Check pin 2 of P100 [CTRL_EN] I suspect it should be close to 5 volts to enable the control board. Q304 appears to be the VS_ON control pin I suspect it tells the control board that the VS voltage is ON and present on the ysus.
IC200 and Q202 are the smps for the 18v. If that circuit is running, 18v comes from D203 but due to protection circuits, IC200 may be turned off.
I don't know what ic200 is post it's number.
Is R206 ok? does it have Vs on both sides?
Also check R329, R330, R331, they connect ZD304 and then to Q304 base, Q803 collector connects to the VS_ON that goes to the ctrl board

Thanks for the replies.
Q304 - reads fine
IC200 - part number was originally 200d6 replaced by 200d1.
Q202 is reading fine
D203 is reading fine
R206 cant seem to locate
R329 -(code 124 which is 120Kohm) - 95
R330 -(124 which is 120Kohm) -95
R331 -(124 which is 120Kohm) -95
ZD304- 0.734

Just before i reached (I didnt touch anything) down to check pin 2 of P100 got a spark near/under q404 will try again tomorrow. Multimeter is playing up again.

[thuss]

Re: 60pb660v flogging a dead tv-shop visit req

ZD304 reads 0.734

[R_J]

Re: 60pb660v flogging a dead tv-shop visit req

R206 is a low ohm resistor next to R559 very near the center of the board (component side) It is the fuse resistor that feeds the Vs to the transformer primary
If you can, what are the voltages on ic200? that should give some idea of what it is doing. This circuit is just a smps.

You should have Vs on one side of R329 and it will drop down through R330 then drop again through R331 and have a voltage on one side of zd304, then there will be the voltage on the other side ov the zener, depending on that zeners value it will either turn on Q304 or not, so it could be for Vs detect ( is there Vs voltage present) or it could be for Vs over voltage detect, where Vs is too high it turns on Q304 turning off the control board.
Just a note: bad zeners can check good, they just zener at the wrong voltage.

[thuss]

Re: 60pb660v flogging a dead tv-shop visit req

Sorry thanks my mate found it and you are right strangely only reading 205v on the one side of the r206 - this resistor was checked several times before

pin 2 on p100 is reading 5.1volts

I will get my mate to check the voltages on the ic200- I suppose he will have to reverse the board with some non conducting material and check the voltages thanks for your help but I am sure he checked that resistor several times before.


My mate replaced the ic200 a few days ago. I will get him to replace it. Thanks again

[R_J]

Re: 60pb660v flogging a dead tv-shop visit req

IC200 - part number was originally 200d6 replaced by 200d1

200D6 = 60kHz operation, 200D1 = 100 kHz operation, so it may or may not work properly in the circuit or may not work at all.
If you only have Vs on one side of R206, it is open, It is there to act likea fuse for the smps circuit, so if ic200 is trying to run at 100kHz that could be an issue.

[thuss]

Re: 60pb660v flogging a dead tv-shop visit req

The electrical shop said it was suitable- all the other values were identical on the data sheet apart from it comes in 40,60 or as 100 kHz - I will try and source a 200d6 may take a week.

My mate remove the pad for leg 7 of the ic200 which is according to the data sheet, not connected so we left it floating i.e not attached would that make a difference? I assume the spark yesterday was the resistor shorting.

[R_J]

Re: 60pb660v flogging a dead tv-shop visit req

Like I said it might work, but the transformer etc was picked to run at 60kHz frequency, Q202 may not like 100kHz either. thats almost twice the operating frequency

[thuss]

Re: 60pb660v flogging a dead tv-shop visit req

will replace it with the 60khz version will update as soon as replaced thanks again

[R_J]

Re: 60pb660v flogging a dead tv-shop visit req

What was wrong with the original ic200? If the spark was the resistor going open, I would recheck Q202 and the resistor on its source.

[thuss]

Re: 60pb660v flogging a dead tv-shop visit req

What was wrong with the original ic200? If the spark was the resistor going open, I would recheck Q202 and the resistor on its source.

There was no picture on the tv and my mate read a thread regarding a 50pn4500/50pn5400 on bad caps where they changed this with some mosfets and the TV came on, it was missing the 18v- so my mate decided to replace it as it it was becoming a nightmare to repair and he had replaced so many components.

Will recheck qq202 etc - can I replace 200d6 with a 200p6? I can get the latter on Monday rather than waiting a week or so.

[R_J]

Re: 60pb660v flogging a dead tv-shop visit req

The 200D6 is SoIC-8 (surface mount) the 200P6 is a PDIP-8 (through hole) So I don't know if you can solder it to the smd pads

[thuss]

Re: 60pb660v flogging a dead tv-shop visit req

Thanks R_J will keep you updated - the 200d1 chip is blown but q202 and the resistors seem fine apart from r206

[thuss]

Re: 60pb660v flogging a dead tv-shop visit req

Like I said it might work, but the transformer etc was picked to run at 60kHz frequency, Q202 may not like 100kHz either. thats almost twice the operating frequency

I checked and the 200d1 operates as you said twice the required i.e according to the data sheet at 116khz whilst the 40 actually operates up to 48khz

[Agent24]

Re: 60pb660v flogging a dead tv-shop visit req

I'd be skeptical about the frequency doubling too. Try the correct chip.

[thuss]

Re: 60pb660v flogging a dead tv-shop visit req

my mate changed the ic with 200D6 and we get the following voltages -please see attached photo components highlighted with yellow lines. I think q202 (5N60) and R214 need to be replaced

[R_J]

Re: 60pb660v flogging a dead tv-shop visit req

Did you not check Q202 before changing the ic? You have 205v on the gate of the fet, it must be shorted, and IF you are lucky you did'nt damage the new ic. The open R214 may have protected part of the ic but, R209 may also be damaged, and if it is not the 10v on the CS pin Very likey DID damaged the ic. It's max voltage seems to be 1 volt.
You also have 205v on the source so the source resistor (R217) will also be open

[thuss]

Re: 60pb660v flogging a dead tv-shop visit req

Yes we did check q202 it seemed fine, on diode test. When you mean the source resistor are you talking about R214? I will replace the q202 and R214 and check for other failed components. R331 R330 and R329 have voltages on them- 137v, 71v,71v etc

Do you think IC201 is ok?

[R_J]

Re: 60pb660v flogging a dead tv-shop visit req

Do I think IC201 is ok? ... Likely not, If it IS damaged it will likely cause Q202 to short. You should not have 205 volts on the fet's gate. that will feed straight back into the ic