Myrica p42-2H green shadows

[nostrike]

Re: Myrica p42-2H green shadows

Turned it down. Stable at 148.1

[tom66]

Re: Myrica p42-2H green shadows

Okay, is there a test point for Va and Vs? It seems strange that you now get stable Vset, but the picture is still bad.

[nostrike]

Re: Myrica p42-2H green shadows

Sorry, turned it clockwise when showing it 148.1. Will try down now

[nostrike]

Re: Myrica p42-2H green shadows

Unstable at all the way down like "normal" position
Clockwise stable at 148.1

[tom66]

Re: Myrica p42-2H green shadows

Most potentiometers on plasma TVs are set up so counterclockwise is reduction in voltage. For some reason this one is different. Just try reducing it. If it becomes stable at a certain point, this indicates that the Vset power supply is faulty for some reason. It could be a bad cap or excessive load. Or a faulty TL431 feedback IC.

[nostrike]

Re: Myrica p42-2H green shadows

I can make it stable at 158. Any higher voltage, it gets unstable.

[tom66]

Re: Myrica p42-2H green shadows

How does it behave if you unplug the connector going to the left hand plasma panel driver board (looking from the rear?) You will not have a picture but it might show if the PSU is unstable under load.

[nostrike]

Re: Myrica p42-2H green shadows

Unplugged left panel driver board. Set Vset at normal position. 195 Stable (like sticker) so something is wrong with left driver board ?

[tom66]

Re: Myrica p42-2H green shadows

Unplugged left panel driver board. Set Vset at normal position. 195 Stable (like sticker) so something is wrong with left driver board ?

More likely a problem with the power supply, being unable to supply the required current. Can you post a closer picture of around here?

By the way, from now on I will refer to that board as the Y-sustain. The Z-sustain is the opposite board connecting to the plasma panel. The Z-sustain is less important but still necessary for a good picture. If you unplug the Z-sustain, does Vset rise again? Without the Z-sustain unplugged you will get a picture, but it will typically be dim, sometimes purple-tinted and slow to change.

[nostrike]

Re: Myrica p42-2H green shadows

Plug Y-sustain back in, unplugged Z-sustain.
Stable at 195

Close up picture you asked for:

[tom66]

Re: Myrica p42-2H green shadows

So this shows that no particular board is causing the problem, but it is the power draw from the plasma panel that is causing it. In which case, it is very likely a power supply problem. My first bet would be the caps for the Vset which could fail without bulging.

[nostrike]

Re: Myrica p42-2H green shadows

I have a lot af caps. Which ones should I change? Also have a professionel Solder Iron

[tom66]

Re: Myrica p42-2H green shadows

I would say replace these RED highlighted capacitors if you can. Do you have an ESR meter? A capacitance meter may suffice for a basic check, but an ESR meter is best.

Can you check the BLUE highlighted resistors - what is the colour code and what do they measure? (You might need to remove the board to do this. If you do so, leave the board unplugged for 5 minutes from the mains (but leave other boards plugged in) before pulling it.)

[nostrike]

Re: Myrica p42-2H green shadows

do not have a capacitance meter or ESR meter. Do you have a good link for one in UK (things are cheap there and also in P&P) In Denmark they are very expensive.

I will pull the board and check colourcode and measure right now.

[tom66]

Re: Myrica p42-2H green shadows

Farnell is good and they have a warehouse in Belgium I think. I would need to know the capacitance and voltage rating to make suggestions.

[nostrike]

Re: Myrica p42-2H green shadows

colour code is :
number 1 : from the top : black, black, yellow, gold - measure - 99,4 ohm
number 2 : from the top : black,blue, yellow, gold - measure - cant measure - counts down from 1000 ohm to -ohm :S
number 3 : from the top black, black, yellow, gold - measure - 98 ohm
number 4 : from the top : black,blue, yellow, gold - measure - cant measure - counts down from 1000 ohm to -ohm :S

Think my digital multimeter is a little funny or I made an error

[nostrike]

Re: Myrica p42-2H green shadows

Now it is a worse/best case scenario.

The TV will not show picture now,
but there is sound. The TV can turn on,
but after 5 seconds, the 2 front leds starts blinking
very 2 second.

Do I measure Va, Vsc, VS, Ve and Vset they are all correct
with Z og Y sustain plugged in.

Do you think the power supply is totally over
because of the volt regulation we tried ?

[tom66]

Re: Myrica p42-2H green shadows

Check all the voltages including Vs.

Also check the fuses on the sus boards. If you plugged them in while the caps were charged, you may have seen a spark, which could blow the fuses on the boards.

[nostrike]

Re: Myrica p42-2H green shadows

Have checked fuses on Y and Z sustain. All good.

All voltages checked. All fits with sticker.

Do you think the 3 three finally gave up?

[tom66]

Re: Myrica p42-2H green shadows

Very unusual for a set to just die like that especially if the fuses aren't blown. Double and triple check everything is definitely seated. And check that you aren't holding the power button down when you work on it, as I have had the same problem get me many times!