Samsung Plasma TV

[Paul Vallandigham]

Re: Samsung Plasma TV

Here's what I got:


PS ON (Pin 1) 3.28V Standby 3.28 Initial Power-up, then rapidly down to 0.11
VS ON (Pin 17) 0 V Standby 3.25 V Initial Power-up BRIEFLY, then 0 V

[Paul Vallandigham]

Re: Samsung Plasma TV

1

[Paul Vallandigham]

Re: Samsung Plasma TV

What about the voltages on the connector at the top left hand corner Va = xx, Vs =xxx

I'll have to get back to you tomorrow. My remote control operator is not currently available to make it easy to grab those readings in the first 3 seconds of power-up (I assume that's what you're looking for. I have readings at that connector post-fault shutdown if that's what you need: Va = 0, 15V = 14.87,Vs = 6.8, Vs #2 = 6.8 [one for the Y board and one for the cable leading to the Y board and then on to the X board, I'm guessing).

[Paul Vallandigham]

Re: Samsung Plasma TV

What about the voltages on the connector at the top left hand corner Va = xx, Vs =xxx

At the connector sending power from the Pwr Supply to the Y board, initial pwr up:

Va = 54.6 V, then discharge (both Va pins)
Vs = 215 V, then discharge (both Vs pins)

The above values hold, regardless of whether all cables are in place, just the cable to the X board (from the Y board junction) is unplugged, or the cable to the Y board is unplugged.

At the X board signal/pwr input connector, Ve-in = 141 using chassis grnd,107 using test pad grnd.

Any advice on how to remove the Y board without damaging it or all the connectors to the Y buffers? I'm thinking to look under those heatsinks. I'm hoping I can remove the heatsinks without de-soldering anything. True?

[maxvalutech]

Re: Samsung Plasma TV

My experience is mainly with Samsung models but your pics look similar. Make sure all screws are out of y board but not buffers and then pull sideways evenly with a very slight wiggle if it helps - the tightness of the connector are mainly in first bit then they let go! Heatsink generally soldered near each corner and screws down the middle but you will see what is what when board detached. The diagnosis made by me is based on popping sounds heard and could be y or x watch for any signs of char on panel under boards. But due to protection circuits in this model power board could still be suspect so no harm in removing it as well for examination.

[Paul Vallandigham]

Re: Samsung Plasma TV

My experience is mainly with Samsung models but your pics look similar. Make sure all screws are out of y board but not buffers and then pull sideways evenly with a very slight wiggle if it helps - the tightness of the connector are mainly in first bit then they let go! Heatsink generally soldered near each corner and screws down the middle but you will see what is what when board detached. The diagnosis made by me is based on popping sounds heard and could be y or x watch for any signs of char on panel under boards. But due to protection circuits in this model power board could still be suspect so no harm in removing it as well for examination.

I popped the Y board off using a flat blade screwdriver between the boards to gently start it loose. No charring on the bottom side or on the plasma panel, and using a flashlight I saw no bulging/burnt MOSFETs under the heatsinks or dry solder connections on the front or the back. Figured I'd try the X board next. Same story. Went for the main board, same story. Re-attached all 3 boards & reconnected everything and now I've lost the sound, too. I figure I'll pop the power board off tomorrow to inspect the back and then start the troubleshooting from scratch to see if any voltages have changed after my disassembly & reconnection.

In any case, the way these MOSFET's are attached, it looks like I would need to invest in a heat gun and/or a motorized vacuuming de-solder gun to get all the connections loose before I could get them off the board -- looks like if I just loosened the heatsink corners, I could end up mangling the leads on the MOSFET's to get to the undersides of the heatsinks and remove the screws. From what I've seen on the internet, those two tools together would be about as expensive (or more) as labor to have somebody else fix it. This is not the easy fix I was hoping for! But it has been a learning experience.

[maxvalutech]

Re: Samsung Plasma TV

Some are easy but most take a fair bit of detective work coupled with knowledge and common sense. Most techs only work down to which board to replace these days and there is reason in that. A check of a few posts in the forums explain how to test the y and x for a short. Now is a good time to check availability of boards for that model and then consider cost involved viz a viz buying a new set (some 65inch here in Oz only $900 odd and generally $12/1300). But there is the sense of achievement when you fix the suckers!

[maxvalutech]

Re: Samsung Plasma TV

My experience is with the older models and it was a lot easier to determine what board bad by voltage tests. Only basic tests done so far but they show that switch on is operating ok which tends to indicate mainboard clear and powerboard half clear. I understand you can test disconnected unpowered Y and X for shorting by setting ohm scale 2000 and probes on Vs power in point and ground when if low reading e.g. 250 or so then short evident - someone correct me if wrong. Buffers not yet looked at as care needed in detaching screen feeds - on the Y side H is High L is Low referring to screen display. Suggest you look on net at ... Samsung Tech Talk Vol 4 Issue 11 and also Issue 10...by search. Loss of sound disconcerting so is connector attached ok both ends and if so is the voltage for sound still present? Would like to see those with more experience chime in here with their comments.

[Paul Vallandigham]

Re: Samsung Plasma TV

I checked what I paid for the set in April 2014 -- $1,800 US, so I'm willing to spend up to about $500-ish to fix it, considering that new similar-sized UHD sets (might as well upgrade if I have to buy new) are running about the same or more. Nothing new on the troubleshooting front -- family & household have currently taken priority and we're using a smaller set from another room as a backup. Hoping to continue troubleshooting tomorrow.