Samsung HP-T5054

[capkid]

Re: Samsung HP-T5054

I've included a pic of the tip I use for my Xytronic iron. It has a well on the end to hold a small amount of solder. A chisel tip should work fine, also. I sometimes intentionally bridge the first three pins of a side then I use that bridged solder to drag along pins on that side so that I can control how much solder is applied; you don't want too much solder or you'll create a mess. When you drag solder, you drag lightly along the "ankles" of the pins, not the feet. Also, liquid flux is your friend. You don't want to work dry. The one thing I like about the well tip is that you can suck up bridges into the well.

http://www.youtube.com/watch?v=b9FC9fAlfQE

[gustav]

Re: Samsung HP-T5054

I couldn't order the solder tips in time, so I hacked the old cheapo iron with a solid tip. Using 150 grit sandpaper, the tip was grounded down to a bevel style and used a small drill bit to scratch some form of a "well" in the middle. Although it didn't resemble any sort of a well, the scratches were enough to hold a small amount of solder. It worked. Also, a great deal of practice using different combinations of a heat gun, paste, and solder in trying to get a consistent result so only one attempt was made on the final "chip". I mean, like all of Friday night, and a good part of Saturday, before finding the right method I felt confident in. Perhaps this way others may find it useful instead of going out and buying an expensive hot-air station or waiting for the right tip to arrive. So far, one outside pin was off track, and I was able to get it right. The right soldering tip is the way to go. Of course a hot air station would be nice, but the cost wasn't justified in replacing one or two chips. Now to replacing the FET's, fuse and the caps. But that will have to wait for until tomorrow.

[capkid]

Re: Samsung HP-T5054

Nice work. I have a hot air station, but I prefer to drag solder with an iron instead of using the station.

[gustav]

Re: Samsung HP-T5054

Put it all together, and still a dead picture. I might have forgotten to replace something, like a diode, etc. While checking voltages and based on the samsucks manual, the x,y,z main board, and logic cables were pulled off the P.S. and the Voltage Sustain (Vs) was still around 209v, the setting was 207. But the logic board cable was the only one pulled, the Vs dropped down to nothing. Is this normal?

The Vsustain test point on the y-main was -190. Power to the Y main was 207-ish, with all cables connected. The Led on the logic is also a solid green, don't know if that's normal. I did not replace Q5501 (B20nk50z), the surface mounted fet, and ZD5502. They didn't appear shorted. 'Don't really want to spend a lot of money on this, for it is a science project to start and it was free. Love the service manual....replace board, replace board.....later. and thanks for help.

[gustav]

Re: Samsung HP-T5054

vscan on the y-buffer

[capkid]

Re: Samsung HP-T5054

It seems like the VS drop with the control board cable disconnected could be normal. I'd more concerned if the opposite were true. How are the rest of your panel voltages?

[gustav]

Re: Samsung HP-T5054

Well, they seem to be fine. But this is really the first time I've worked on a plasma. I know plasma's are kinda like the red-headed step child of tvs, which is why it would be a great learning experience. So far, the PSON is 3.35, Stb is 5.17, Vson is 3.22 and the Vs to y and x main are both 209. And the other is the Vscan on the ymain is 187. So it would appear the psu is looking ok. My guess is the y-main is the problem, but that's my opinion. But probing around with checking out the smd resistors, caps, and diodes, so far they look good. There's a good chance something was missed. The other surface mount fet, can be replaced just for integrity's sake. But I'm getting some readings. So it's not short.

Other things, the y-main led is not lit up, and there is no shadows or even any kind of faint light on the screen. After researching some more, this "appears" to be the typical scenario of the samsung plasma's problems. Blown fe3407, blown cap and pico fuse at the incoming connector. So, I starting to get to obsessed with it and gonna have to back it down a bit. Frustrations starting to set in. But that will make the triumph even that much more sweeter. If you need me to try something else out, I'll be very eager to do so. I think we are closer that I imagine we are. How can one get experience without trying. later and thanks again

[capkid]

Re: Samsung HP-T5054

Well, some of us actually prefer to work on plasmas vs. LCDs . If you have an oscilloscope, you can do the check on page 59 of the service manual. It sounds like you still have Y-main issues, though. Unfortunately, I had to cut bait on one of my HP-T5054 Y-mains. It was too far gone. I ended up buying another non-working Y-main and repairing it instead.

[gustav]

Re: Samsung HP-T5054

Maybe you can answer this one. With power on and checking voltages. I noticed on the MOSFETS, lower set, the third one Q5503 was measuring around 20-50v I believe on the Gate, pin on the far left if facing it. However, the other 88n30w are measuring around 188 to 200 or so. I am not trying to see which one is blown, as they were just replaced, but to see where the voltage is dropping. Also, the y-main heat sinks are cold whereas the x-main and the PSU's are warm. Checked of course after the set was unplugged. So, definitely the y main is the board of concern. My question is why is that one showing a much lower voltage than the other exact ones? Is it due to some other smd or component around that Mosfet causing it to read much lower? And before I switched out the mosfets, that same one was reading lower than the others. Gate to drain, I think. Any thoughts?

[gustav]

Re: Samsung HP-T5054

I ordered the other surface mount Fet, B20nk50z. If that doesn't work, then I have to consider getting a different y-main board.

[capkid]

Re: Samsung HP-T5054

Yeah, I'd jump ship if the mosfet replacement doesn't work.

[Glitcher]

Re: Samsung HP-T5054

I would consider rechecking the mosfets you just replaced again. There were some incidents I read that they might have blown again if not all the ground screws were placed when testing it on.

[gustav]

Re: Samsung HP-T5054

Got the ohter mosfet today, but a larger size soldering tip isn't here until monday. So we'll see then. I believe that one, smd mosfet is blown as well.

[gustav]

Re: Samsung HP-T5054

Put the surface mount mosfet in, and no go. No video noise just a black screen. I'm beginning to think it's a blown panel. What's puzzling is the y-sustain green led is not lit up. And the board is getting the right voltage, 206.7v. So, this was a freebie, I just want to chuck the entire tv. But as soon as I do....., So, it goes into storage for now until I have some more patience to make a decision to keep working on it, or toss it. I guess the first thing to do IS to see if the panel is bad. Here we go again.....later

[capkid]

Re: Samsung HP-T5054

I wouldn't spend much more time or money on this TV. It's pretty old, and there are plenty other better quality TVs out there. Having gotten this far, it's hard to just give up on it, though.

[kevinm34232]

Re: Samsung HP-T5054

This is the problem with these older tvs you get.. I have 3 or 4 that have been laying around that I want to get fixed or at least find out what's wrong to sell the good parts just to get rid of them, and you get stuck in limbo.. Hate to just throw away the good panels and majority of good parts without figuring it out!!

[capkid]

Re: Samsung HP-T5054

This is the problem with these older tvs you get.. I have 3 or 4 that have been laying around that I want to get fixed or at least find out what's wrong to sell the good parts just to get rid of them, and you get stuck in limbo.. Hate to just throw away the good panels and majority of good parts without figuring it out!!

I have four lying around, also. I'm fairly certain the panel is shot on one, but it's such a nice TV and the panel was working at one point; I want to give it one more shot.

[gustav]

Re: Samsung HP-T5054

Yea, thanks for the help. The problem is I've somewhat of an O.C.D. type who can't let it go until I figure it out. Most likely the majority of the ppl in here are the same way.

I got maybe 20 bucks or so in it. And since I just got a 42 lcd fixed last month for my own use, this one just happened to pop up in the ads for free. I figured why not. I was hoping to get it fixed cheap so I can give the lcd to my daughter. It's just a matter of patience before one shows up again in the ads, but meanwhile the white straight jacket will go on. I'll try to continue to mess around with it but not with the up most enthusiasm.

[krygods]

Re: Samsung HP-T5054

I'm preparing to perform a buffer IC removal and replacement and I found this PDF that talks about QFP removal and hand soldering. Thought others might find it useful also.

[ljintexas]

Re: Samsung HP-T5054

I have repaired two of them. Both cases I had to have the power supply rebuilt by someone with the right gear..mucho FETs, diodes, and capacitors..even a couple ICs. Both sets still working...two years down the road.