Panasonic TCP50GT20

[rcpilot82]

Re: Panasonic TCP50GT20

If you removed them, getting the cables back in is very fiddly, and it's hard to do right. You'll have to reseat them all until the picture works better.

Well at least I didn't blow anything up...yet...

I'll go play and post back..
Thanks

[rcpilot82]

Re: Panasonic TCP50GT20

IT'S ALIVE! Lol. All is good, I got a flashlight and got a close look at the connectors and was able to re-seat them all.

FWIW: the time on the unit is 4695:40 Hrs

NOW, is it worth doing a fan mod or should I just put the case back on?

Also, Upon inspection of the refurb. board from best-buy it was visable that the repair to this board was in the same location as my original board blew.

[tw2005]

Re: Panasonic TCP50GT20

IT'S ALIVE! Lol. All is good, I got a flashlight and got a close look at the connectors and was able to re-seat them all.

FWIW: the time on the unit is 4695:40 Hrs

NOW, is it worth doing a fan mod or should I just put the case back on?

Also, Upon inspection of the refurb. board from best-buy it was visable that the repair to this board was in the same location as my original board blew.

Hey that's fantastic, if you have a chance get some clear close up shots of the board for us to look at. It may give some clues.

[rcpilot82]

Re: Panasonic TCP50GT20

Hey that's fantastic, if you have a chance get some clear close up shots of the board for us to look at. It may give some clues.

Which board do yo want close ups on? the bad one or the good one?

Thanks for all the help guys

[tom66]

Re: Panasonic TCP50GT20

Can we ask for both ?

[rcpilot82]

Re: Panasonic TCP50GT20

Can we ask for both ?

Lol, Yes you can. I can't get pics of the back side of the new board cause it is installed already. I'll try and snap some pics tonight.

Tom, While I have your attention, What are your thoughts about adding cooling and my ideas above? Do you have any input on voltage sources on the PS that can be used for fans? I can get 48VDC fans and 24VDC, 12VDC fans.

http://www.mpja.com/48VDC-4-3_4in-X-...nfo/19005%20FN

I think 2 would be sufficent. I just need a power source that is switched with the TV power.

[tom66]

Re: Panasonic TCP50GT20

The PSU has a 15V rail. You can run a 12V fan off that, but it'll sound like a jet engine, so I suggest either a 24V fan, or a series resistor to limit the speed.

[rcpilot82]

Re: Panasonic TCP50GT20

The PSU has a 15V rail. You can run a 12V fan off that, but it'll sound like a jet engine, so I suggest either a 24V fan, or a series resistor to limit the speed.

OK, Looking at the service book I see 3 locations where there is a 15v output.

Connector Pin
P11 4
P25 1 and 2
P6 3

Should I not use any of these outputs? I assume the ground would be any of the mounting screws with the lugs on them? I Agree a 24V fan is the way to go to keep the noise down. I attached the PS layout for ref.

[tw2005]

Re: Panasonic TCP50GT20

Which board do yo want close ups on? the bad one or the good one?

Thanks for all the help guys

I'm primarily interested in any evidence of SMD replacements. You've already confirmed the fet driver ic which is one of the easier things to check but I'm worried I'm going to miss some very tiny device which is shorted.

I got lucky and stumbled on a tiny inverter chip shorted on all 3 boards , IC773 , 5pin smd, located near that large cap C813.

If I miss something and it simply does not work ok, but if it destroys other devices then I won't be happy.

[rcpilot82]

Re: Panasonic TCP50GT20

Pics of BAD board.

[rcpilot82]

Re: Panasonic TCP50GT20

Pics of Refurb. board

[rcpilot82]

Re: Panasonic TCP50GT20

I came across this today:
http://www.ebay.com/itm/1x-Power-Sup...item3ccdf1e52c

Do you guys think this would be a good solution to drop down the 15 volts from the PS? I have plenty of fans that are 12v and with this I could adjust the output voltage to keep the fans quiet. Good Idea??

[rcpilot82]

Re: Panasonic TCP50GT20

Well, I ordered the power supplies, I got a 3 pack as I have other uses for them if the fan idea does not work out. Does anyone have any interest in seeing the fan mod I will be doing? If so, I'll do it and post more details about it. Otherwise I am just gonna get it done and put back together.

[tom66]

Re: Panasonic TCP50GT20

I would be interested!

To be honest I would just use a series power resistor. A cheap DC-DC like that could kick back a lot of unwanted noise into e.g. the audio or panel circuit causing problems.

If your fans are, for example, 12V, 0.15A rated, and you have three of them, and you want to run them at 7V (nice and slow), then calculate the resistance required according to R=V/I. 0.45A total, 5V drop (7V output) required, 5/0.45 = 11.1 ohms. 12 ohms and 10 ohms are both close. A 12 ohm resistor would dissipate 2.43W, so use a 5W one.

[rcpilot82]

Re: Panasonic TCP50GT20

I would be interested!

To be honest I would just use a series power resistor. A cheap DC-DC like that could kick back a lot of unwanted noise into e.g. the audio or panel circuit causing problems.

If your fans are, for example, 12V, 0.15A rated, and you have three of them, and you want to run them at 7V (nice and slow), then calculate the resistance required according to R=V/I. 0.45A total, 5V drop (7V output) required, 5/0.45 = 11.1 ohms. 12 ohms and 10 ohms are both close. A 12 ohm resistor would dissipate 2.43W, so use a 5W one.

My concern with using a resistor was the heat factor. The fans I will be using are both 12v. and .17A rated (.34A for the pair) computer power supply fans. I ran them on a 6V NiMh pack last night and it seemed a bit too slow for my liking but was very quiet.

Output from PS: 15V
Fan voltage required: 8-10V
Voltage needs dropped: 5-7V
So given R=V/I,
R=5/.34=14.71 (15 ohm resistor)
R=7/.34=20.59 (21 ohm resistor)

Is my above thinking correct? I'll try the DC-DC for Grins N Giggles, but I'd like to have a backup plan ready to go.

I'll be getting some measurements this weekend for the fan mounts so I can laser them out and have them ready to go when the parts get here.

[tom66]

Re: Panasonic TCP50GT20

Looks good, I forgot you had 15V not 12V. A 22 ohm is the closest to 21 ohm standard. 15 ohm is standard. A 22 ohm resistor will dissipate 2.54W.

Power dissipation won't be a concern, because the plasma panel itself dissipates nearly 250W full power. The resistor can be placed in airflow, if deemed necessary.

[tw2005]

Re: Panasonic TCP50GT20

Thanks for the shots. It'll be interesting to see your mods

[rcpilot82]

Re: Panasonic TCP50GT20

Well, The fan mod works.

Below are several pictures of how it all came together. I used pop rivets to assemble everything so there is no drilling on the TV. I also used existing holes to mount everything.


assembling and mounting the fan shroud;

1. Cut out acrylic fan shroud, I had a junk piece of material and since this was not going to be a visable Mod. I used that.

2. Mount fans, I decided at the last minute to use 3 fans instead of 2 so that all the boards would get some air moving over them.

3. Wire fans, all joints were soldered and heat shrink applied. Reds to red, blacks to black, no brainer. All wires were connected to the supplied jumper with the DC-DC.

4. I loosened the one screw about 1/3 down on each of the mounting supports. This allowed me to slide the wires for the outboard fans under the mounts so they would not pinch.

5. Pop rivet the shroud into place. 4 rivets using 4 existing holes.

Done.

Mounting the DC-DC.

1. using a scrap piece of acrylic, I made a mount for the DC-DC. This required a few holes and notches to clear the solder joints of the Thru Hole mounted components on the board.

2. mount the DC-DC on the acrylic with a rivet.

3. mount the DC-DC to the side of the mount support nearest to the SS and A boards.

4. plug in the connector from the fan shroud assembly to the "OUT" of the DC-DC.

Done.

Wiring the DC-DC.

I found that Connector 11, Pin 4 had 15VDC output when the unit was switched on and 0 volts when turned off. This is the connector to use.

1. Using the jumper provided with the DC-DC I soldered a ground lug to the black wire to mount it to the screw on the PS directly above connector 11

2. I then wrapped the positive end of the jumper around the Pin 4 between the PCB and the connector housing and soldered it.

3. plug in the Jumper to the "IN" on the DC-DC.

Done.

Final setup:

Check all wiring for chaffing spots or interference, and power up the set. Have a small flat screwdriver on hand to adjust the pot on the DC-DC for best speed/sound combination. Once you are happy unplug, wait a few mins and re-install the back cover. Hopefully the boards will enjoy the airflow for many years.

[tw2005]

Re: Panasonic TCP50GT20

That's a top effort, seriously. Not exactly a hatchet job. I did'nt think those boards got too hot in this but every bit helps. However if there was one part which had me concerned it was the large heatsink on the A-board which was virtually too hot to touch. not sure what your boards are like ours are slightly different.

[rcpilot82]

Re: Panasonic TCP50GT20

That's a top effort, seriously. Not exactly a hatchet job. I did'nt think those boards got too hot in this but every bit helps. However if there was one part which had me concerned it was the large heatsink on the A-board which was virtually too hot to touch. not sure what your boards are like ours are slightly different.

Thanks,

I have been using a 50" LG plasma as a backup to this one while I fixed it. I can tell you the Panasonics gets MUCH hotter than the LG does. When the Panasonic was in service, you could get within a ft of it and feel the heat around it. The LG you have to touch it to feel any tempature change. Unfortunatly, for the LG, I feel that the Panasonic has a better quality display than the LG. I'll be putting the P-Sonic back into full service tonight.