Sceptre x322bv-hd powers up w/sound-but no picture

[cbr6861]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

Heres the back of the board. looking with magnifying glass-q23 & d17 look questionable.

[budm]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

BTW, did you check those two caps that DGTECH suggested you to test in post 2?
I think more likely that the MOSFETS are not getting the GATE Drive signals.

[budm]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

That section is for driving the GATE DRIVE TRANSFORMER, as you can seem they compliment with each other, there are three devices in each set, it is setup as a bridge drive to drive that transformer. So check all six of them.

[cbr6861]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

BTW, did you check those two caps that DGTECH suggested you to test in post 2?
I think more likely that the MOSFETS are not getting the GATE Drive signals.

not yet, not sure on how to test with my analog meter for capacitance.
I have an electronics store really close to me which I'm heading to so I will just pick up the 2 while I'm there & replace them.

[cbr6861]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

That section is for driving the GATE DRIVE TRANSFORMER, as you can seem they compliment with each other, there are three devices in each set, it is setup as a bridge drive to drive that transformer. So check all six of them.

can these be checked in the circuit or do i need to pop them out to test

[budm]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

Try doing the comparison reading in the circuits first.

[cbr6861]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

Try doing the comparison reading in the circuits first.

here are the readings i got in 'diode mode' on the dmm. both mosfets read the same

[budm]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

Resistance wise look OK.
How about those 6 transistors that drive the primary side of the Gate drive transformer in post 21?

[cbr6861]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

don't mean sound like a bozo, as this is all new to me , and i appreciate all you've done so far. Are you referring to the area that i circled in post 21? D17 & 18, Q22, 23, 24, 25

[budm]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

Pictures are not quite clear, it looks like it has 3 Q devices and 2 D devices, and yes, they are what I referring to.

[cbr6861]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

your right there are 6-
here are the results:

[budm]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

OK, I do not see any of them with '0' (shorted or really Ohms) reading. This not going to be easy to troubleshoot without the diagram.

[cbr6861]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

what do you think?, I mean i can find one on ebay to replace (thats no biggy). was kinda bent on trying to find out what the problem is ...BUT the reality is ...its a cheap tv and i guess the line has got to get drawn at some point before it gets to ridiculous. For myself, I saw this as a chance to learn more about electronics and the strategy behind the diagnosis.
As far as diagrams go....I would have no idea where to even get/find one.
Do you feel the problem lies on the board alone or could it be beyond the board?
I don't even know if the back lights even work! as this was already broken when i got it.
whats your gut saying?

[budm]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

@ this point we know that the inverter section does not work, we do not know if the lamps are good or if the main board, the T-CON are good since we cannot really see the pictures on the screen. It will be good to have the diagram if you want to learn, without it it will be hard to explain what is going on the board. I do not know how much the new power supply is.

[cbr6861]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

they are around 40 coming in from china on ebay. SJ is outta stock as well as most everybody in the US from what I'm finding.
I don't have a clue on how to get a diagram for this. where would i need to go/look.

[budm]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

I have no luck finding the diagram for this MIP320FL-2.

[cbr6861]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

from all the posts i've been reading on badcaps with this same model tv...the inverter section of the power board does appear to be the culprit in solving their problem. but WHAT exactly in the inverter section is at fault. That is the mission i'm on.

[cbr6861]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

I have no luck finding the diagram for this MIP320FL-2.

yes...that would be a problem then.

[budm]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

@ this point, it seems to be that there is no drive signal top drive the Gate of the MOSFET to turn it on and off, the MOSFETs then drive the high voltage transformer.
I have seen this board in the badcaps forums, so you are not the only one with the problem. Having the scope to probe some points on the board may lead to some indication as to where the problem is.
The SJ board does not have the same layout on the bottom side as your board. It has only three semi devices instead of 6 for driving the Gate drive transformer.
http://www.shopjimmy.com/megmeet-mip...t-inverter.htm
So may be some improvement are made to the board.

[cbr6861]

Re: Sceptre x322bv-hd powers up w/sound-but no picture

I decided to pop off the big transformer (the one w/ yellow tape around it) and have a looky. Something caught my eye that seemed odd. One of the wires running to its lead on the output side appeared to be slightly burned.
When I put my meter across the 2 input leads i got a beep. when i put them across the 2 output leads i got nothing.
Im not sure how to test a transformer , so i decided to do the same with another transformer i had lying around. I got beeps from both sides on that one. I put up some pics. it was hard to take a pic as i could almost not see it w/ my magnifying glass.
Thoughts?