Dell 42 inch plasma no picture

[shelby5041]

hi i have been working on this dell 42 inch plasma


no picture

tested buffers and they test not shorted

all the voltages on this old model are suppied by power supply

ve
vsc
vs
vg
va

all are within 1-2 v of specs except vs

vs should be 207v and is actually 233v

i go to try adjust on ps but the adjustment is on lowest setting..can not turn anymore counterclockwise

any ideas?

could the vs voltage be an issue?

i have repalced the y board once....didnt fix issue...and actually burned a pico fuse on my replacement y

the z board is connected to ps directly.....does not come from y board

[shelby5041]

Re: Dell 42 inch plasma no picture

all the voltage adjustments on this model tv are on the ps


no adjsutments are made on y or z on this model

[shelby5041]

Re: Dell 42 inch plasma no picture

correction......after installing the replacement y board which i installed and only connected upper buffer

the smell was upper buffer shorting out ....which it wasnt shorted before..but now is shorted

the fuses on the y replacement board are all good

is it a bad y board? that shorted out the y buffer? ? or could the high vs voltage from ps be the issue?

[dick_barton]

Re: Dell 42 inch plasma no picture

I would have thought the high VS is a problem which should be looked at since most threads seem to indicate not adjusting this by no more than +/- 10V

[shelby5041]

Re: Dell 42 inch plasma no picture

yes...i agree...but its only adjustable up.....its maxed a low....

there are potentiometrrs on y but not labeled

the ones on ps are labeled ve vsc vs vsetup va

[shelby5041]

Re: Dell 42 inch plasma no picture

on a potentiometer is clockwise increase voltagr and counterclock decrease?

my vs is way high but my adjuster is maxed out counterclockwise

[tom66]

Re: Dell 42 inch plasma no picture

Not always, can be the other way. It's not consistent.

If you're worried about damaging X and Y, adjust with them disconnected and two 120V 60W (or thereabouts) light bulbs connected in series, between Vs and GND.

See this page for an example:


This is not your panel. This is only an example of a different panel and how testing would be accomplished.

Take care as the bulbs will be at high voltage potential.

[shelby5041]

Re: Dell 42 inch plasma no picture

tom the vs adjustment is on power supply so can i disconnrct y and x and adjust clockwise to see if it does indeed lower the voltage?

the dell tv insides are samsung parts

the y has some white voltage adjusters but not sure for what...they arrnt labled vs vsc etc

[tom66]

Re: Dell 42 inch plasma no picture

Vs adjustment is always on the power supply. I have no idea what the other adjustments are. I would suggest that adjusting them is a bad idea if you do not know what they do.

You need to see the Vs when under load some of these power supplies are unstable under no load and voltage goes high. So the lightbulbs were a suggestion as they are readily available. Note you cannot use CFL/LED bulb.

[shelby5041]

Re: Dell 42 inch plasma no picture

vsc and vsetup and ve are all on ps

i tpically see some of those on y and z but not on this tv

anyways....now i understand the load issue....i recall metering the voltages on this tv with y and z disconnectrd and voltagds werr fluctuating but when i measurrd connected thry werr stable

[shelby5041]

Re: Dell 42 inch plasma no picture

tom when i got this tv a while back..it had typical plasma problem

power on and then would power off

i tested buffers and they were shorted.....and the y had a blown pico fuse on it so i assumed the y board and buffers were the issue...but then tested voltages and the vs voltage of 233 actual vs 207 specs seems not right but not sure this would take out those 3 boards?



the biggest problem is trying to find good replacement boards....i have bought 3 y boards from ebay and all have been bad....also 1 set of buffers were bad...

its hard enough for me to troubleshoot plasma tvs...makes it even harder when you cant feel confident about replacement boards working condition

to me lcd tvs are way easier to troubleshoot...plasmas are a pain

[shelby5041]

Re: Dell 42 inch plasma no picture

what i may do is just unhook the y and z and turn the adjuster a little clockwise just to see if it has any indication of going lower

question...can this be done while tv is off? ..then turn tv back on and test?...

if it goes higher ill know to just turn all the way back ccw until it stops like it is currently

[tom66]

Re: Dell 42 inch plasma no picture

Read my post above I told you exactly what to do now stop creating extra work for yourself. You need to do the test with the bulbs because these PSUs are not guaranteed to regulate well with no loads.

Vs being high CAN kill boards. And your meter may not be giving you a fully accurate reading. It could have transients or oscillation that is much worse.

Once you have set this up give the measurements for Vs and we will go from there. I won't answer any other questions otherwise because you need to focus on ONE ISSUE at a time.

[shelby5041]

Re: Dell 42 inch plasma no picture

Hi..my original troubleshooting was correct....it was a bad y and bad buffers

It took me 6 diff purchases to finally get an operational y board and went through 7 different purchses to finally get a good set of buffers

What a pain"....

If people would stop selling bad boards as good i would have fixed this tv long time ago and way less headache