Need guidance scoping YSUS board.

[johnboy1313]

I've started another thread about the TV already. I would normally wait for someone that has already been commenting to chime in but I have circumstances that lead me to start a second thread. I have to take the scope back tomorrow morning and I'm not sure how to use it to scope my board.

https://www.badcaps.net/forum/showthread.php?t=24596

I'm hoping that one of you that has been through this before could guide me through it. I'd rather take the thing back unused than blow one of the channels. Here's my last post from the other thread.

I found a point on the y buffer that says waveform. The problem is that I have next to no idea what I'm supposed to do. I know it makes me sound really ignorant. I do have experience with a scope. I took two years of part time EET classes at the local junior college but that was at least three years ago. What am I setting the scope to? Other than the waveform point, where do I touch for the other point? CH 1 to waveform, EXT TRIG to to ground? Seriously, I can do this, but not without some guidance.

I really don't like starting a new thread but time is not on my side. Today's my birthday and the day is pretty full. It would be really cool if I could get the waveform before I go to bed tonight. Once I have that, I can go back to my original thread.

[ghiotom]

Re: Need guidance scoping YSUS board.

Assuming your input can accept up to 400 volts, put your probe on 10x and volts/div to 100 volts. Ground goes to any nearby screw or other point attached to the chassis. You might want to pull or unscrew your probe clip and just insert the tip into the hole marked waveform on the board. Triggering will be hard. You may get a fairly stable waveform setting trigger to AC line ( 60 Hz in US) or you may be able to trigger in on the peak of the Vset voltage if you have a waveform. I wouldn't worry about external triggering, you're just looking for a waveform. Take a picture and post.

[johnboy1313]

Re: Need guidance scoping YSUS board.

I was only able to get up to 50v/div but still got a couple of good pics.

[tom66]

Re: Need guidance scoping YSUS board.

Is that it? Can you post a larger timebase image? That does not look right.

[johnboy1313]

Re: Need guidance scoping YSUS board.

Not a problem give me a second.

[johnboy1313]

Re: Need guidance scoping YSUS board.

Well, I'm not real clear on what you want. I think you mean you want to see a shot from a longer time period.

I'm really not sure what's going on here, but this is in RUN mode.


Here's zoomed in a little more in STOP mode


Here's zoomed in really close in STOP

[ghiotom]

Re: Need guidance scoping YSUS board.

Try setting the time to 2 milliseconds.

[tom66]

Re: Need guidance scoping YSUS board.

Looks fine..

[johnboy1313]

Re: Need guidance scoping YSUS board.

Looks fine..

So I guess I'm looking at a bad panel then. It would figure the first plasma I try out seems to be working fine.

[tom66]

Re: Need guidance scoping YSUS board.

No, check X-main first... Post pic if you need help locating test point. Unlikely to be a bad panel.

[johnboy1313]

Re: Need guidance scoping YSUS board.

Will do. Tom, you are such a help man. You have no idea how much I appreciate it, mate. I'll give it a look.

[johnboy1313]

Re: Need guidance scoping YSUS board.

Is the X drive the same as the X main? If so, this is what is in my set. Mine is buried and I don't want to expose it until I need to.

http://www.shopjimmy.com/lg-6871qrh082a-xrrbt.htm

[tom66]

Re: Need guidance scoping YSUS board.

Nope, different. On yours it is Z-sustain.

[johnboy1313]

Re: Need guidance scoping YSUS board.

http://www.shopjimmy.com/lg-6871qzh067a-zsus-board.htm

Here's a link to my Z-SUS, is it the point labeled Vzbias?

[tom66]

Re: Need guidance scoping YSUS board.

You want to check it at that orange beaded device next to the white barcode label.

[johnboy1313]

Re: Need guidance scoping YSUS board.

Thanks.

[johnboy1313]

Re: Need guidance scoping YSUS board.

You want to check it at that orange beaded device next to the white barcode label.

From Z-SUS

[johnboy1313]

Re: Need guidance scoping YSUS board.

Any thoughts?

[tom66]

Re: Need guidance scoping YSUS board.

They look absolutely perfect. Do you have any light emission from the screen at all?

[johnboy1313]

Re: Need guidance scoping YSUS board.

No, I've never turned it on in a completely dark room, but I don't think it does. I wonder if this thing has a hidden crack in the panel somewhere.