Was It a Mistake to Buy a Vizio P4 for $10?

[Paul678]

It says May 2003 on the back, so it's clearly an older model.

I figured there was a slim chance this was an easy cap and
fuse fixer-upper, and if not, I could sell the parts on Ebay. But
the problem is I didn't see many listings for the Vizio P4, but that
could mean simply less competition when I do list the boards. I'm
not sure what the market demand for this model is, but there wasn't
too much info on the archives here or anywhere else on the internet,
so I figure I may have blown $10. OTOH, as soon as I sell just one
board off this guy, I'll think it was worth it! The Ebay market DOES
amaze me sometimes!

Ok, here are some pics:







At first, the relays clicked when turned on, and the LED on
the main board turned on and stayed on with the relay click.
But totally black picture, and no sound from speakers.

The 2nd pic is the Y-sustain, and I measured:

Vcc = 5V
Vf = 14-15V
VW = 0.3 V
Vs = 4 V

And the same on the X-board, but
with:

Vxg = 0


The panel says: VsSET=173, VxgSET=160, so it
looks like the Vs and Vxg are totally off.

Then, after playing around for a few minutes, the
LED on the main and the relay began to shut off automatically
after about 3 seconds. During the 3 seconds, there
is sometimes a faint arcing noise, and the lights
in my house dim just barely, so it's clearly
some sort of crowbar, current-limiting protection
scheme that shuts off the relay. Also, the relay
will turn off even when the Y-sus and X-main
main cables are disconnected from the power supply.

But it's intermittent, and sometimes I can get
the LED and relays to stay on.

So it looks like a bad power supply to me, but
I'd like to know what you guys think. Like how
should I test to make sure that the buffers and
Y-sustain and X-main are still good?

I found this one:

http://www.ebay.com/itm/Gateway-GTW-...item1e69ec5498


And added it to my watch list.....

Thanks for any advice.....

[tom66]

Re: Was It a Mistake to Buy a Vizio P4 for $10?

It's a WVGA panel - 852x480 pixels - not even HD. You'd be lucky if it sells for more than $30 working.

[Paul678]

Re: Was It a Mistake to Buy a Vizio P4 for $10?

Obviously I should have done some more research on this one.

I got desperate to crack open a tv, ANY tv!

Do you think the parts are worth anything on Ebay? Or is this mainly
scrape metal?

[tom66]

Re: Was It a Mistake to Buy a Vizio P4 for $10?

Obviously I should have done some more research on this one.

I got desperate to crack open a tv, ANY tv!

Do you think the parts are worth anything on Ebay? Or is this mainly
scrape metal?

Maybe, list them for 99p plus shipping, it's free. Or keep it as a test TV. Try to get it working, then play with the setup/setdn timing and Vs/Va/Vset/etc. voltages, to see what it does - it should do similar things to other newer TVs so useful for testing ideas on. Try probing the drive waveform with a scope (10X probe & 400V rated only, though.)

[Paul678]

Re: Was It a Mistake to Buy a Vizio P4 for $10?

Ok, so based on the info in my first post, do you
agree that this may be a power supply issue?

On the Magnavox 42MF231D/37, when the Y-sus
was disconnected (no-load), the Vs was still
+200 V or so. Shouldn't Vs=+173V and Vxg=+160V
in this case?

There aren't any obvious bulged caps or burned components
on the top of the PS, but as everyone knows, looks can be deceiving.

This stuff is addictive, no doubt.....

[tom66]

Re: Was It a Mistake to Buy a Vizio P4 for $10?

What about other supply voltages? The Vs/Va are switched, they don't come up in standby mode.

[Paul678]

Re: Was It a Mistake to Buy a Vizio P4 for $10?

Again, for the other voltages I measured:

Vcc = 5V
Vf = 14-15V
VW = 0.3 V


Not sure what the VW is, but it's certainly appears too low.

On the Magnavox 42MF231D/37, the Vs and Va were there
pretty much all the time. Don't you need these voltages
just to put the menu on the screen?

Additionally, there is a 2 pronged connector labeled DC
with the (-) side labeled VAUX. The (+) measures
around +250V, and the (-) side measures -65V or so.
These go to the skinny audio board at the top of
the first picture. Don't know if these are the
normal voltages.....but doesn't +250V seem high
for an audio board?

[tom66]

Re: Was It a Mistake to Buy a Vizio P4 for $10?

Again, for the other voltages I measured:

Vcc = 5V
Vf = 14-15V
VW = 0.3 V


Not sure what the VW is, but it's certainly appears too low.

On the Magnavox 42MF231D/37, the Vs and Va were there
pretty much all the time. Don't you need these voltages
just to put the menu on the screen?

Additionally, there is a 2 pronged connector labeled DC
with the (-) side labeled VAUX. The (+) measures
around +250V, and the (-) side measures -65V or so.
These go to the skinny audio board at the top of
the first picture. Don't know if these are the
normal voltages.....but doesn't +250V seem high
for an audio board?

Check for bad diodes in the Vs/Va supply; check the PFC is working and also check the auxillary rails (e.g. 5V, 3.3V) are there - the ones going to the main board.

[tom66]

Re: Was It a Mistake to Buy a Vizio P4 for $10?

And if you're really bored...

http://www.youtube.com/watch?v=HxNd97PIar0