HITACHI P50TP01E Y-Buffers/Sus problem

[tom66]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

USB scopes are generally a bit rubbish.
You can do well just with a good, used analog scope with at least 20MHz of analog bandwidth.
Such examples are often available for under $50 on trading sites and eBay.
Dual channel, 400V input minimum.

[reaper57]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

Maybe, ICs just kept frying every time I turned it on. Turns out the Vscan was bad, but the owner didn't want me to continue with my troubleshooting. I was really hopping to fix this TV, but oh well.
On the other hand I realized that most of the FETs on the Y-sus board are MOSFETs... (I know it should be obvious, but I guess I just didn't really think about it). So, I guess the oscilloscope tom was talking about was for testing those. It still sounds like a good idea to get one, but I'm not really sure about which one. I prefer a USB one, but I hear that people don't like them very much and prefer standalone ones. Do you think that this is a good one and if not what do you recommend?
http://www.ebay.com/itm/SainSmart-DD...item461487cb94

[Shinju]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

Are the buffers good?

[reaper57]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

Well guys, I forgot to mention that the tv wasn't mine, and the owner no longer wants it fixed. I told them that I had some progress, but I guess the repair was going to cost him more than this whole 8 year old tv so he just didn't want to bother with it anymore.
Anyways, thanks to everyone who tried to help me, especially tom66.
I guess it's back to my other projects for me. :P

[reaper57]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

Hmm, looked like one but it isn't.
Can you get a clear close up photo of the whole Y-sus... if necessary split it into several images to ensure they are clear and in focus.

I think I found the transformer that you are talking about (it should be the first attachment). There is also one similar to this one on the top of the board, I took a picture of it as well. I've also attached pictures of the Y and X-sus boards.

[tom66]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

Hmm, looked like one but it isn't.
Can you get a clear close up photo of the whole Y-sus... if necessary split it into several images to ensure they are clear and in focus.

[reaper57]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

There appears to be a small white transformer near the bottom of the Y-sus / Y-drive board, can you get a picture of it?
https://www.badcaps.net/forum/attach...8&d=1412248465

The pictures are in the attachments and the model of the samsung tv I scraped is PS-50Q97HD.

[tom66]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

There appears to be a small white transformer near the bottom of the Y-sus / Y-drive board, can you get a picture of it?
https://www.badcaps.net/forum/attach...8&d=1412248465

[reaper57]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

Do you have an oscilloscope available?

No, unfortunately I do not, I have a capacitance meter, though. But do you think that the caps have gotten so bad that they are messing up the voltage this bad (or is the oscilloscope for testing something else, sorry I'm new to these types of devices)?

P.S. I scraped a 50" Samsung plasma with a cracked panel a day ago (I don't have it at home, and I don't remember the model, but I will check it tomorrow and post it here). The boards aren't the same, but some of the components should be the same, and if needed I could swap FETs, caps, ICs etc, between the TVs.

[tom66]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

Do you have an oscilloscope available?

[reaper57]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

Do you (or anyone) have any ideas about what could be causing unstable the voltage? Also can someone, kindly explain to me, how to test the Y-sus, X-sus and anything else that might be the the reason for my problem? I have no problem with desoldering MOSFETs/FETs and testing each and everyone of them. Btw huge thanks for the help so far.

[reaper57]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

So that was DC volts, red on red circle, black on black circle? If so, your Vscan supply has a serious issue... this is what is destroying your buffer boards, I suspect.

Yes, that is correct negative on black positive on red. Also after removing the last chip the picture ot the top of the screen (the only one that was normal) started vibrating, but I suspect that might be because of the missing components from the buffers, and maybe this is the same reason that the voltage isn't stable? All of the cables going into the Y-sus are comming from the X-sus, so that probably means that the problem could be in the X-sus, right?

When changing the caps on the power supply there were two 270uf caps and one of the 270uf caps I had, when measured showed only 245uf so I put that in with a 330uf cap that showed 290uf. I think that they are filtering the same current so the effect should be the same as having two caps at ~260-270uf right?
I've marked the changed caps with red.

[tom66]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

So that was DC volts, red on red circle, black on black circle? If so, your Vscan supply has a serious issue... this is what is destroying your buffer boards, I suspect.

[reaper57]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

Ok, I did what you asked me, two times. The first time the Vsc was 125v and went up to 212v when picture appeared then down to 180v when the picture changed (probably a message appeared, it was on AV so it was searching for signal I guess the message was about that, but for me it was just white lines), then it went up to 212v again and 180v when white lines appeared in the middle of the screen (a no signal found message I think)
The second time, 100v at start, 90v for less than a second, 212v on the first white lines, then 180v, then 105v for 2s and then 180v at the second white lines.
The voltages that appeared only for a little could be because the tv starts with no indication about which input it's set to then is says AV at the top and then it disappears.

[tom66]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

See here

[reaper57]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

DC wrt to the floating ground point (buffer ground plane), but AC wrt to the chassis.

My multimeter was set to DC and started making buzzing noise with the negative probe touching the chassis. Can you help me locate a place to get the floating ground point from? Or will using the chassis work?

[tom66]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

DC wrt to the floating ground point (buffer ground plane), but AC wrt to the chassis.

[reaper57]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

Well, you will have to be quicker next time... something is clearly amiss with the Vscan supply as I can't think of anything else that would cause that.

Well I did short it by mistake... It was when checking the Vs at the power supply port, there was a flash, but the tv didn't even turn off. And it was before the tv even gave any picture, it was before I started removing chips and after I removed one of the buffers. And after a few restarts the tv kept giving me the same black screen as before. My friend told me that I probably just drained the caps.
I just desoldered the bad chip and am about to clean the solder. And a quick question the current at R812 is DC right?

[tom66]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

Well, you will have to be quicker next time... something is clearly amiss with the Vscan supply as I can't think of anything else that would cause that.

[reaper57]

Re: HITACHI P50TP01E Y-Buffers/Sus problem

P.S. Again on the lower buffer.