Shout out to all techs:Rebuild or Replace

[tech2014]

We all work with Tvs and want to provide the best service to our customers. As a business owner, I try and rationalize whether or not it is better to rebuild a board or just replace it. Finding parts is sometimes a hurdle to overcome. Ordering parts from China, and hope they are not fakes. Some boards are also hard to find, and when they are found, they are usually expensive.

If you have a TV with shorted parts on a Ymain or Xmain, do you rebuild the board or just order a new one. When you rebuild, do you just replace the shorted components, or all of the MOSFETS and IGBTs, even if they measure ok in circuit.

[ReeceyBurger123]

Re: Shout out to all techs:Rebuild or Replace

Depends if I can find the parts I will almost always re-build boards if I cant replace.

[tech2014]

Re: Shout out to all techs:Rebuild or Replace

same here. When you rebuild, do you replace all the parts or just the ones that test bad in circuit.

[tom66]

Re: Shout out to all techs:Rebuild or Replace

Rebuild over replace where possible, but that's not always practical or cost effective.

[Alastair E]

Re: Shout out to all techs:Rebuild or Replace

I tend to rebuild where I can

As to what gets replaced--If say, SUS_Up pair, one failed, Both get replaced--Along with SUS_Dn pair--Even if all the other three test OK.
--These work together--so a short in say, SUS_Up would strain/damage SUS_Dn pair, so they Cant stay on the board...

Same goes for the ever problematic ERC side of things....

[tech2014]

Re: Shout out to all techs:Rebuild or Replace

thanks guys

[tom66]

Re: Shout out to all techs:Rebuild or Replace

To add to this...I *virtually* always repair power supplies. 95% of them get repaired. They're easy to diagnose with meter, scope, light-bulb and some knowledge of operation.

Main boards - about 25% of them get repaired. Most times repair is not practical.

Sustain boards - about 75% of them get repaired. Sometimes repair is difficult, or the board is very cheap and repair isn't worth doing.

[vinceroger69]

Re: Shout out to all techs:Rebuild or Replace

This is from another thread but the same set your working on toms advice was to replace some driver chips too not sure if you saw this thread.

The IGBT is bad if shorted, but there may also be other IGBTs bad in the same area. Often the IGBTs are arranged in half-bridge pairs, a high and low IGBT for the sustain voltage, for example. If you find the low bad, you must replace the high, and vice versa, unless you can be certain they are all ok. It's usually simpler just to replace them.

Also, I would always replace any driver chips which control the IGBTs, this is because in some cases the IGBTs can damage the drivers when they short. If this is the case, turning on the set with new IGBTs but old drivers would cause the new IGBTs to burn up, as they would be given incorrect gate drive.

[Shinju]

Re: Shout out to all techs:Rebuild or Replace

Mainboard repairs are my bane, I really wish I could have saved some of the ones I tossed as some of them were really hard to track down and now they are super expensive.

But Tom66 summed it up exactly.

[tech2014]

Re: Shout out to all techs:Rebuild or Replace

I agree tom, power supplies are easy to repair. I have not had as much luck with Y or X main boards. I have been replacing the shorted parts and even all the gate drive IC, but still having boards short out again at power up. I guess it takes experience and a little luck to get it done.

[tom66]

Re: Shout out to all techs:Rebuild or Replace

I agree tom, power supplies are easy to repair. I have not had as much luck with Y or X main boards. I have been replacing the shorted parts and even all the gate drive IC, but still having boards short out again at power up. I guess it takes experience and a little luck to get it done.

If you use a bulb you can't go too badly wrong. I had an LG 60PZ950T in for repair with a bad Z-sustain. I got the repair wrong twice, but because I used a 100W bulb in series with the Vsus path, only one IGBT went bad each time, and the rest survived, significantly reducing the cost of the repair. If I hadn't used the bulb, I'd have to replace six IGBTs every time. Also, having a scope is extremely useful.

[tech2014]

Re: Shout out to all techs:Rebuild or Replace

I have a scope but it is only 100MHZ. I never used a bulb because I have no idea how to hook everything up and if I do it wrong I'm afraid I will destroy something lol. Are there any sites that show how to do this setup. I know how to use a bulb to test power supply but not X or Y main VS failures.

[vinceroger69]

Re: Shout out to all techs:Rebuild or Replace

I have a scope but it is only 100MHZ. I never used a bulb because I have no idea how to hook everything up and if I do it wrong I'm afraid I will destroy something lol. Are there any sites that show how to do this setup. I know how to use a bulb to test power supply but not X or Y main VS failures.

one of toms videos showing with a bulb in series
https://www.youtube.com/watch?v=ROYHWY79784

[tom66]

Re: Shout out to all techs:Rebuild or Replace

I have a scope but it is only 100MHZ. I never used a bulb because I have no idea how to hook everything up and if I do it wrong I'm afraid I will destroy something lol. Are there any sites that show how to do this setup. I know how to use a bulb to test power supply but not X or Y main VS failures.

I have a 100MHz digital scope (hacked Rigol DS1074Z) and it works fine -- actually it's perfect for plasma TVs. The maximum sustain frequency is roughly 200kHz, so even a 20MHz scope would be adequate.

For the bulb test, the video Vince linked is the gist of it...you just want to cut ALL the Vs lines on the connector and install the bulb in series. Or if the board has a Vs fuse, you can remove that and put the bulb across it.

[ReeceyBurger123]

Re: Shout out to all techs:Rebuild or Replace

same here. When you rebuild, do you replace all the parts or just the ones that test bad in circuit.

If its bad caps I replace any crappy ones on the board and if its a board that I know has other faults I correct what I can on it, if its something like IGBTS only the shorted ones and possibly the drivers etc.

[tech2014]

Re: Shout out to all techs:Rebuild or Replace

thank you very much for all the help guys. So I just take the bulb holder power cable and splice one cable to the VS line and the other to where?

[tom66]

Re: Shout out to all techs:Rebuild or Replace

thank you very much for all the help guys. So I just take the bulb holder power cable and splice one cable to the VS line and the other to where?

To the sustain board...you're placing it in series with the Vs line of the TV. This is essentially the same as how you'd use a bulb with the AC mains, you're just using it on the plasma panel DC side instead.
Note, since US bulbs are 115V rated, they may not last long at 200V DC; therefore, you may want to source 130V rough-duty bulbs or see if you can buy 230V ones somewhere.

[tech2014]

Re: Shout out to all techs:Rebuild or Replace

awesome. So I just have to remove the VS supply going from the power supply to the Y or X main, and install the bulb on the VS line.

[ReeceyBurger123]

Re: Shout out to all techs:Rebuild or Replace

I need to get a scope but saving for a car atm and got too much on to buy one.

[michael dranfield]

Re: Shout out to all techs:Rebuild or Replace

Rebuild, theres no job satisfaction in just replacing a board , any one can do that, if a IGBT or transistor is short always replace the driver IC, a transistor can be tested , an IC cant.