Maxent MX-42HPM20 No Sound, Bad Video

[Jonny Accelerant]

I took this in trade for some computer work, broken, so I've never seen it work. And I don't know how it broke, if it went out slowly or due to a sudden event like a lightening strike, or was dropped, etc...

I think the screen is good as it shows chaotic "something" (noise). Every once in a while you see ordered lines, but never a set-up menu, etc...

The power button goes from amber to green, but the visual display in both states is the same (see photos). Also, applying signal from a computer via VGA cable has no effect on what is displayed. On turn on, there is an audible pop sound, like a relay activating, and once when I unplugged it, I heard an audio noise from the speakers, but otherwise there is no sound at all, as if it were completely squelched.

A visual inspection with the 1st, smaller access cover removed shows that all the capacitors look good, no evidence of burning, etc... Later this evening I will take the entire back off and do a more thorough job of visually inspecting the components. I'm hoping it's nothing more than a few bad caps and I'll be fully functional.

I've done some reading both on this site and on the internet in general, and there doesn't seem to be a single "most likely cause", but if anyone knows one, I'd appreciate the savings in time. Of course, and any other help I might receive.

FYI, I'm a very basic component troubleshooting tech. Got trained in the military 30 years ago and have barely touched it since, however in the last month I've successfully repaired two LCD monitors by replacing a handful of caps, so there's that. I was trained in radios, and have never troubleshot a TV before. From my reading, I'm suspecting that this isn't going to be a simple matter of finding bulging caps, but this is the 800 lb. gorilla that has (literally) been sitting in my living room for 2 years and it's time has come. I'm fixing it, or I'm breaking it forever and throwing it away. Any help appreciated, and thanks in advance.

[aaronwt6]

Re: Maxent MX-42HPM20 No Sound, Bad Video

The static on the screen is making me think bad ZSUS but the distinct horizontal line across the top is throwing me off. I'd start by checking the fuse on the Z-Sustain board and go from there. Maybe Tom of one of the other plasma gurus will chime in. As far as it having no sound, I'm guessing that's simply because it has not source connected, or you are on the wrong input if one is. Volume could also be turned down.

[tucocaps]

Re: Maxent MX-42HPM20 No Sound, Bad Video

Wow! Haven't seen the Maxent name in awhile. I took one in for parts about a year ago. HEAVIEST TV I've ever tried to lift. I'm curious if your set also weighs as if the stand/bottom is made of lead?

[Jonny Accelerant]

Re: Maxent MX-42HPM20 No Sound, Bad Video

As far as it having no sound, I'm guessing that's simply because it has not source connected, or you are on the wrong input if one is. Volume could also be turned down.

I suspect that's true about the audio. I heard a audio amplifier "pop" once when it got unplugged. It has a computer video signal and no audio atm. Maybe later I'll connect a video signal with audio to see if that side works.

HEAVIEST TV I've ever tried to lift. I'm curious if your set also weighs as if the stand/bottom is made of lead?

It's extremely heavy. Lots of metal chassis in there. I'll be taking the back off either tonight or tomorrow to give me greater access to the components (for visual inspection), so I'll see then why it weighs so much.

[Jonny Accelerant]

Re: Maxent MX-42HPM20 No Sound, Bad Video

I didn't have time to do anything with the TV, but I did spend some time doing research. Here's the best thing I found tonight:

http://www.cnet.com/news/bringing-a-...from-the-dead/

First useful thing I've ever found on Cnet, written by the first Cnet author I've read that was not a complete dumbass.

Useful Fact #1:

I also discovered that my specific Maxent was internally identical to sets from LG, Vizio, Toshiba, Zenith, and others, which I thought might make finding replacement parts easier.

Useful Fact #2:

About a million tiny screws later, I had the back of the Maxent TV off, and could see the four main boards inside. A power board, a processor board, and the Y and Z sustain boards.

This defines the scope of possibilities. Like doing the border on a jigsaw puzzle.

Useful Fact #3:

...the blog post included specific part numbers for a compatible Y-SUS board I could use to search on eBay (those being EBR31872801 and 6871QYH053B)

Not ready to call anything bad yet, but from what I've read a bad Y-SUS board goes hand-in-hand with a bad "fast blow" fuse, so maybe the first thing I'll do is start pulling fuses and testing them. I'm wondering, if I find out all the fuses are good, does that mean that the Y-SUS and Z-SUS boards are good? The Y-SUS repair kits I see online contain a big-ass IC looking thing, and a few fuses, which implies to me that when the big-ass IC thing blows, the fuses go with it. Or do the blown fuses cause the IC thing to go? Or does C cause both A & B? If so, what is C?

If I drop $50.00 on a new Y-SUS board, will C cause it to go bad again? Seems like this is a common problem. Common enough to keep some eBay vendors busy selling repair parts, yet not much information (so far) on what causes them to go bad. Multiple manufacturers used identical parts, so you'd think those parts would be of high quality. Design flaw? Bad power coming from the power board? Heat?

I sent a PM to one of the eBay repair parts vendors, asking about the quality of the replacement IC boards vs. the OEM. Maybe the new parts fixed whatever went wrong at the factory?

[Jonny Accelerant]

Update: ZSUS is now Prime Suspect

So I took the back of the TV off and gave it a through visual inspection. No obviously swollen, blown or leaking caps. Pulled the 5 fast-blowing fuses off (that I could find), and they all tested short. Decided that of the 4 major board, the ZSUS looked like it was the easiest to remove, so I pulled it and discovered that the large IC chip (what coppell tv repair calls the " IPM hybrid IC" or "IPM") seems to be leaking something. Took pictures (see attached) and you can see the spread pattern emanates from the large black pad on the chassis, stains the pc board a light brown on the way down and pools at the bottom of the board. Also some grey shreds of the obviously overheated rubber pad are still stuck to the pc board.

But before I declare victory and pull the board and order a replacement, I'd like some input, because I wonder if the gook might not be from the rubber pad itself deteriorating, and the liquid is the cause of the problem as it might be conductive, or capacitive, or corrosive, or whatever. I'm half-tempted to clean it up and put it back on. And I'm also tempted to desolder the IPM and clean-up behind it, inspect it, etc... because what if there is something underneath that is the cause of the problem, and not the $50 IPM itself?

Also, I wonder how the IPM comes off the board. I see the threaded ends of two screws through the top of the heat sink. Looks to me like it needs to be desoldered off the pc before the heat sink can be removed, and I'm probably going to need to purchase a desolder gun.

[Jonny Accelerant]

Re: Maxent MX-42HPM20 No Sound, Bad Video

Here's a really nice video I've found. Guy walks you through step-by-step desoldering and resoldering the ZSUS IC chip.

https://www.youtube.com/watch?v=Y8MNQYXw8E0

Also he gives part numbers for the IC chips:

Old IC: YPPD-J018E
Replacement IC: STK795-820 and maybe STK795-821

Good information here. It's a different manufacturer, but I'm getting the idea that these are all basically the same inside, Vizio, LG, Maxent, etc... He says that the Vizio is an LG with the power board manufactured by Vizio. Also says that the YSUS and ZSUS are the same chips, and there's at least 3 compatible part numbers for them. YouTube author ("norcal715") recommends replacing both Y and ZSUS IC's as a matter of SOP and I'm wondering if others agree.

Best source for these IC's seems to be eBay.

Also, I tested the 5V, and the other two "V" voltages and they were good, so I'm thinking the power board is good. Wondering whether I should pull the YSUS board or just order 2 IPM's.

[Jonny Accelerant]

Important Question:

Can someone tell me why I should NOT purchase two of these from NewEgg at $28.00 each, when they are being sold for almost twice that in eBay?

http://www.newegg.com/Product/Produc...9SIA35C1NB7434

[Shinju]

Re: Maxent MX-42HPM20 No Sound, Bad Video

Looks like an LG made panel, atleast parts are easy to get!

[Jonny Accelerant]

Today's Plan

Can someone tell me why I should NOT purchase two of these from NewEgg at $28.00 each, when they are being sold for almost twice that in eBay?

http://www.newegg.com/Product/Produc...9SIA35C1NB7434

Today's plan is to hold off on buying these IPM's until I pull the YSUS IPM and verify that it is in fact the same part as the ZSUS IPM, and if they are the same, to just go ahead and buy two of them from NewEgg at $28.00 each, plus about $9.00 in shipping and a 5 to 15 day delivery window.

Unless someone has a better idea, or a reason to go in a different direction. At this point I feel that I've done everything that I can think of, that I have skills to do, and without any other advice this is the best option to me. What I'd LIKE to do is measure voltages around the boards in order to determine for certain that one or both of these IPM's are bad, but have no idea on how to do that. I'd also like some expert to swoop in, hold my hand and patiently walk me through the troubleshooting process, but it doesn't look like that is going to happen, and as I've mentioned earlier, I'm either fixing this thing, or I'm breaking it for ever and exporting it to the nearest landfill. Later this evening I'll pull the YSUS board and get a look at the components there, and unless something dramatic happens (such as I find an obviously blown capacitor that I can quickly and cheaply replace as an intermediary step before replacing one or both IPM's, or I discover that the YSUS and ZSUS are NOT the same), I'll order the parts from NewEgg tonight, or tomorrow at the latest.

Also it would be nice if someone could give me good opinions on the leaking stuff on the ZSUS board (see photos) and whether it came from the deteriorating rubber pad (my theory), or a component in the IPM, or what. And also if anything bad will happen if I simply remove that bad and throw it away. Seems to me that the pad's purpose is to prevent shorting against the metal chassis behind the ZSUS board, but it's 1/2" thick, and there is NO WAY that board is going to flex low enough to short to chassis ground. It would break first. So since it's obvious to me that the pad's purpose shouldn't be to prevent shorting, then either it has some other, unknown (to me) purpose, or it's a stupid design and it really serves no function at all. Be nice to know which is most likely.

[aaronwt6]

Re: Maxent MX-42HPM20 No Sound, Bad Video

The pad you are speaking of is a thermal pad (heat sink). If you were to remove it, the IPM would overheat almost immediately.

I would not mess with the Y-Sustain board at all if I was in your position. If the Y-Sustain was bad, the screen would not light up like yours does. It would either be flickering, or completely dark. IPM on the Z-sustain is definitely my vote.

[aaronwt6]

Re: Maxent MX-42HPM20 No Sound, Bad Video

Oh, and the brown stuff on the board is probably from the original manufacturing process. Most of these have at least some on it. Yours is heavy but does not indicate a problem of any sort.

[Jonny Accelerant]

Re: Maxent MX-42HPM20 No Sound, Bad Video

The pad you are speaking of is a thermal pad (heat sink). If you were to remove it, the IPM would overheat almost immediately.

I would not mess with the Y-Sustain board at all if I was in your position. If the Y-Sustain was bad, the screen would not light up like yours does. It would either be flickering, or completely dark. IPM on the Z-sustain is definitely my vote.

Oh, and the brown stuff on the board is probably from the original manufacturing process. Most of these have at least some on it. Yours is heavy but does not indicate a problem of any sort.

Thanks for all that. After I posted about it, I realized some of the brown stuff is different than the wet stuff. The brown stuff is at the top of the board, is crusty and dry, and came off with mechanical action (scrubbing) and alchohol. The wet stuff comes directly from this pad.

Is there no way that this pad is the cause of the problem? The rubber/material deteriorates and shorts, or has capacitance, or whatever, and causes the IPM to fail? Is there an "upgrade" for this heat sink? Something metal and with a fan? If the IPM will overheat immediately due to the absence of this POS chunk of rubber, then maybe that's why it went bad to begin with. Do they sell this stuff new as a replacement part? What's it called? Is there something better? This stuff is damp and gooey, like the steering wheel on an old car where the rubber & plastic is deteriorating. How come I've never heard of this gooey, dripping rubber heat sink stuff before? Is it common? Is it a common cause of failure? Can I replace it with something better? How hot does it get in there anyways? Maybe a small fan would help? There's a couple of empty jacks where I could run a small northbridge fan or similar.

To the issue of the YSUS board. If I'm going to replace the Z and wait for deliver on a $28 part, shouldn't I order two and do both? Not even necessarily because it needs it, or because (as the YouTube video author says) because it MIGHT need it, but because it's cheap and I've got the thing opened-up anyways?

What if I swapped my presumably bad ZSUS for my presumably good YSUS IPM's? Could doing that help definitively diagnose the problem(s)? I'm thinking "what if" here. What if I swap the IPM's and the symptoms change to what you've described as having a bad YSUS board. That would be helpful, no?

Thanks for your help. The fate of my Maxent 42" LCD TV, and @$50.00 of my money is in your hands, oh swami guru.

[Jonny Accelerant]

Re: Maxent MX-42HPM20 No Sound, Bad Video

I realized after my last post that I would have to desolder these IPM's from the board before I could even look at them, and I have to buy a heat gun and a desolder gun before I do that, so... I'm thinking I'm going to just buy two of these and while waiting for them to be delivered, I'll get the tools I need ready.

[mmartell]

Re: Maxent MX-42HPM20 No Sound, Bad Video

I'm repairing an LG which uses the same or similar zsus boards. I read here somewhere that the two large inductors(?) on the right side of the board suffer from cold solder joints. You can see the joints in the first pic of post#6 to the left of the ipm footprint. Have a close look and reflow with fresh solder if necessary.

Your link to newegg doesn't say if those ipm's are new or pulls. I don't see the wisdom in replacing a functioning ipm with a pull as outside the aggravation of replacing it you stand a chance of shortening the lifespan of the board instead of lengthening it.

I found a board for $24 stated as good which lo presented the same symptoms. I will have a replacement tomorrow but am not optomistic as this failure seems all too common and with the ipm failing passively sellers believe the board to be good apparently. Good luck.

[Jonny Accelerant]

Re: Maxent MX-42HPM20 No Sound, Bad Video

I'm repairing an LG which uses the same or similar zsus boards. I read here somewhere that the two large inductors(?) on the right side of the board suffer from cold solder joints. You can see the joints in the first pic of post#6 to the left of the ipm footprint. Have a close look and reflow with fresh solder if necessary.

I assume it's those two large orange "loop" looking things? That looks like a perfect opportunity to test a new heat gun. I assume that I should be able to visually see physical cracks in the weld under magnification?

Your link to newegg doesn't say if those ipm's are new or pulls. I don't see the wisdom in replacing a functioning ipm with a pull as outside the aggravation of replacing it you stand a chance of shortening the lifespan of the board instead of lengthening it.

Agreed with the logic of that. Waste of time exchanging one used part for another used part. My assumption was that NewEgg wouldn't be selling used parts, but I'll look into that. The price indicates used, but I assumed the absence of any mention of "used" or "working pulls" meant "new".

I found a board for $24 stated as good which lo presented the same symptoms. I will have a replacement tomorrow but am not optomistic as this failure seems all too common and with the ipm failing passively sellers believe the board to be good apparently. Good luck.

Thanks for that. I'm about to order the 2 ZSUS boards. I'm half-tempted to order a bunch of them and resell them.

[Jonny Accelerant]

Sanyo STK 795-821 Plasma Driver Module from NewEgg

http://www.newegg.com/Product/Produc...9SIA35C1NB7434

Had the following text chat with "angelhehai" from Shenzhen Shanhai Technology Ltd., which is selling the part through NewEgg:

[7:44:58 PM] *** angelhehai has shared contact details with J. Accelerant. ***
[7:45:03 PM] angelhehai: How are you ?
[8:51:24 PM] J. Accelerant: I am fine.
[8:51:37 PM] J. Accelerant: Is the part in the link to newegg new?
[9:41:59 PM] angelhehai: we have shop in newegg
[9:59:04 PM] J. Accelerant: Is the part NEW?
[9:59:34 PM] angelhehai: yes
[9:59:41 PM] J. Accelerant: Do you understand the question?
Is the part NEW? Not USED, not "working pull", not "refurbished" not "factory second" not "second quality". I'm asking is the part NEW?
[9:59:44 PM] J. Accelerant: sorry
[9:59:53 PM] J. Accelerant: okay good, that's all I needed to know
[10:00:09 PM] J. Accelerant: You should put that on the newegg listing because some people think it is not new.
[10:00:18 PM] J. Accelerant: It should say that the part is new.

There should be a internet meme created for berating chinese sales reps for failing to have even the most basic skills need to do business with westerners. Engrish is a good start, but also descriptions of their products, and oh, here's a good one from the email auto-responder I got:

My dear , Thanks for your email , I will reply you in 2-3 hours . if you have urgently questions . Please contact me by tel:86-13148812796 , or add my skype : angelhehai , or my alibaba ID : hkshanhai .

"My Dear", huh? Do I get my parts with a Happy Ending, or at least a fortune cookie? Can I have egg rolls with that?

Anyways, I'm ordering two of these. Might not use the 2nd one, so I might have one available for sale at some point in the future. I'll report here on the shipping progress, as well as the acquisition of my heat gun and desolder gun.

[mmartell]

Re: Maxent MX-42HPM20 No Sound, Bad Video

Yes the orange rings.

My replacement zsus (third if you count the failed one original to the set) is dead also in the same way. Cold ipm heatsink but functioning zbias circuit. Just for fun I ran the set without any zsus board and it looks the same.

Looks like I will be ordering an ipm module.

[Jonny Accelerant]

Re: Maxent MX-42HPM20 No Sound, Bad Video

Just for fun I ran the set without any zsus board and it looks the same.

That does sound fun. I think I'll do that too.

[mmartell]

Re: Maxent MX-42HPM20 No Sound, Bad Video

Coppell TV has three price levels for these:

New - $55 approx
Pulled - $37 approx. Imported good cond.
Pulled - $25 Pulled by Coppell themselves.

I believe the $25 is culled from the working board of a ysus/zsus combo sent in for rebuild. Conventional wisdom says when one fails the other is likely not far behind. Meh. I think i will order one and spend a few dollars more on active cooling for each heatsink.