Philips 42" Plasma 42PF7320

[osci]

Re: Philips 42" Plasma 42PF7320

well done dmitt!!

[Dgtech]

Re: Philips 42" Plasma 42PF7320

With my finger on the PNX8550 chip (that Dmitt explained earlier), very hot right before TV shutdown. They must have these chips in a lot of their sets. Sucks that this chip doesnt seem to be replacable. I'll have to try to find a replacement board or try to find a heatsink that will fit.

[Dgtech]

Re: Philips 42" Plasma 42PF7320

So I immediately took the stupid blue jelly-foam crap off the viper chip and the other large chip on the back of the SSB. I applied a thin layer of Artic Silver 5 thermal paste on the chips and then installed a couple aluminum heat sinks I got off Ebay that I had to mill down because they were about 1/16" too tall to fit in the cage.

Pictures are soon to come. The blue jelly - foam is actually a form of heat transfering pad that should have been connected to the heatsink (the backplane "cage"). Adding a heatsink may or may not fix this problem permanantly due to the difference in size of the heatsink you can fit in that area versus the backplane itself acting as a heatsink - being more open for air flow.

I am going to modify (correct) what is there already. I'll try to use thermal paste on the pad - maybe both sides (between pad to heasink and pad to chip).

It's a good thing I didnt buy a replacement board before doing more investigation.

[dmitt25]

Re: Philips 42" Plasma 42PF7320

Pictures are soon to come. The blue jelly - foam is actually a form of heat transfering pad that should have been connected to the heatsink (the backplane "cage"). Adding a heatsink may or may not fix this problem permanantly due to the difference in size of the heatsink you can fit in that area versus the backplane itself acting as a heatsink - being more open for air flow.

I am going to modify (correct) what is there already. I'll try to use thermal paste on the pad - maybe both sides (between pad to heasink and pad to chip).

It's a good thing I didnt buy a replacement board before doing more investigation.

I didn't know for sure dgtech, but I assumed that's how the blue pads worked. They're a pretty sad excuse for a cooling system. The heatsinks I installed actually rest against the backplate even after I milled them down. I wish I would have taken off maybe a few more thousanths because there is an ever so slight bow to the board when the screws are installed. I may have jumped the gun on the new board but the way I see it, I've got a backup now in case my heatsink theory doesn't work.

My next step is to figure out how much amperage I can pull from an unused 4 pin socket on the power supply that is currently supplying 12v x 2 pins and GND x 2 pins. If it can handle it, I'd like to hook up 2 120mm fans to this socket and blow some air over the back of the Tv.

[Dgtech]

Re: Philips 42" Plasma 42PF7320

Funny you mentioned about the fan cause I had a thought about that too. The only thing though, there is so much over voltage and over current protection in there, I'd be afraid to even try without creating a new problem. If you do this, then I'd fuse it carefully. If anything add a localized laptop style fan right near the chip somehow.

About the heatsink, if it is pressed up against the backplane, I'd probably leave it as such. At least you know it's making solid contact with the paste and chip.

I've been stuck at work today so I havent even tried my theory yet.

[PowerAmpFreak]

Re: Philips 42" Plasma 42PF7320

...just like my thoughts about improving airflow in my newly fixed 50PF7320.
Since I got rid of the entire audio amp board I will use the +/- 18V audio supply for an own fancontrol.
It's amazing how lifetime of power semiconductors can be improved by lowering the working temperature by a few degrees.

[retiredcaps]

Re: Philips 42" Plasma 42PF7320

...just like my thoughts about improving airflow in my newly fixed 50PF7320.

I read that another forum member hooked up a usb fan to his lcd monitor (usb port) to keep it cool. Maybe you can find a quiet usb fan and do the same as many of these TVs have usb ports?

[dmitt25]

Re: Philips 42" Plasma 42PF7320

I read that another forum member hooked up a usb fan to his lcd monitor (usb port) to keep it cool. Maybe you can find a quiet usb fan and do the same as many of these TVs have usb ports?

Not a bad plan.. I was considering doing something slightly similar although quite a bit more ghetto. Since I put the TV all back together, I really don't feel like taking it all apart again.. mostly the weight of this sucker. I thought since my HTPC is sitting on the stand right below the TV, maybe I could just run a cable out the back of the computer case utilizing one of the empty Molex connectors on the power supply and running two fans attached to the outside of the case thru the venting.

The way I see it, any moving air, especially from bottom to top and then out looks like it will help a great deal.

[Dgtech]

Re: Philips 42" Plasma 42PF7320

PowerAmpFreak - Did you end up changing the board for yours as well? I am noticing no change with either way of trying to manage the heat. I have tried the pad different ways as well as putting a heatsink on the chip (with thermal paste).

[dmitt25]

Re: Philips 42" Plasma 42PF7320

PowerAmpFreak - Did you end up changing the board for yours as well? I am noticing no change with either way of trying to manage the heat. I have tried the pad different ways as well as putting a heatsink on the chip (with thermal paste).

At first I ran the old board with the heatsinks but when the new one came in the mail a couple days later (I still hadn't put the back on the TV yet) I decided to use it instead. I didn't want to take the chance that the old board may still be defective in some way and I'd have to open it all back up again. I'm pretty lazy. Well, not THAT lazy. If I were truly lazy, I would have just gone out and bought a working TV I'm not half as smart at troubleshooting as most of the people on here, so I took the easiest way out and gave myself a little insurance.

I hope you're successful in getting yours to work, the old board I have does work with the heat sinks, but I didn't do any serious testing with it. How big is the heat sink you're using? mine covers the whole chip and then like an 1/8" of an inch extra on all 4 sides.

[PowerAmpFreak]

Re: Philips 42" Plasma 42PF7320

PowerAmpFreak - Did you end up changing the board for yours as well? I am noticing no change with either way of trying to manage the heat. I have tried the pad different ways as well as putting a heatsink on the chip (with thermal paste).

Nope, I didn't change the board. Everything appears to be OK now after changing two 3300uF/10V caps in the main psu. But fact remains, it has a good 9600 hours in its lifetime counter, and I really like to have this TV for a while, so why not do everything I can to help it survive a little longer.

[Dgtech]

Re: Philips 42" Plasma 42PF7320

I have to put this aside just for this weekend as I am removing carpet and installing laminate flooring in my second bedroom.

Here are the pictures of the set that I have. I may have to try a larger heatsink as I just tried one that was longer in length but 1/4 inch thinner than the chip. I used a heatsink off from a MOSFET from a scrapped board. I'll have to pick up the right sized one tomorrow from my electronics store, that and more thermal paste. The spacing that I've noticed is about 1/4inch for max height of the heatsink needed.

Philips, Magnavox, Samsung = The work of the devil!!!

[PowerAmpFreak]

Re: Philips 42" Plasma 42PF7320

Philips, Magnavox, Samsung = The work of the devil!!!

Hehehe Great said!
They are those forces who want us to quit component level repair and just swap modules or buy a new tv each three years.

[PlainBill]

Re: Philips 42" Plasma 42PF7320

Hehehe Great said!
They are those forces who want us to quit component level repair and just swap modules or buy a new tv each three years.

Hey, if you want to replace a 256 pin IC or a BGA chip, go right ahead. Maybe replacing TO-263 packages is your idea of time well spent. While you have been whining about 'the good old days' perhaps you should remember the cost, quality, and reliability of the TVs you used to troubleshoot to the component level.

Perhaps you have forgotten the 1960's RCA, GE, Philco, etc TVs with the all tube chassis. Mechanical tuners, a couple of dozen tubes, colors that would drift as the set warmed up, a caddy full of vacuum tubes. And the customer whimpering when you handed him a bill for $50 after you spent a couple of hours running down the leaky cap or resistor that had drifted, then tuning the sound decoder.

Take a look at the schematic of the SSB in the 42PF7320 and tell me with a straight face that you would be able to troubleshoot that to the component level in two hours. Or that it would be possible to reduce it to a couple of snap-in parts.

What is really hilarious is that one of the whiners was unwilling to troubleshoot an audio amp problem. An amplifier whose schematic, part's list, and parts layout is included in the service manual!

PlainBill

[PowerAmpFreak]

Re: Philips 42" Plasma 42PF7320

What is really hilarious is that one of the whiners was unwilling to troubleshoot an audio amp problem. An amplifier whose schematic, part's list, and parts layout is included in the service manual!

PlainBill

Well, the "whiner" has to defend himself I did troubleshoot the audio amp problem and came to the conclusion that the output-fet ic was bad, the TDA8925ST (IC7701 in the service manual), but I wasn't positive to buying spareparts since I simply don't need a 15W audioamp driving internal speakers, when I like my surround system better. Makes sense, right?

I'm sorry if I put my fingers on a sensitive subject, but I do still like component level repairs more than board swap troubleshooting.
I have no problem in changing giant ic's, we have great tools for SMD soldering, microscope, etc (No tools for BGA soldering unfortunately)
but it's very hard if there are no ic's available to buy.

Of course, I get your point, some boards are simply extremely complex, multi layer boards with complex processors and so on, this will still be very hard to repair even if there were spareparts available.

I think we both are right, we may see things from different angles.

[dmitt25]

Re: Philips 42" Plasma 42PF7320

Just a quick update:

Ran some wires from my HTPC's power supply to a couple 120mm fans at the back of the TV. Doesn't seem to do much. There's just SO MUCH HEAT in this TV. It's almost like I need a 3 foot long squirrel fan at the top just to suck some of it out. It was sooo much cooler with the back off, wish there was a safe way to run it that way.

[PowerAmpFreak]

Re: Philips 42" Plasma 42PF7320

How did you do this test? I'm little surprised that fans as big as 120mm didn't do anything. Remember that a few degrees lower temp means pretty much in lifetime of power semiconductors. It's very "logarithmic" so to speak.

[Dgtech]

Re: Philips 42" Plasma 42PF7320

A slight variation of dmitt's fix is what I have now tried and seems to work. Taking powerampfreak's suggestion of a fan - I got a low profile heatsink and fan from an old motherboard chipset. I placed the heatsink (about 1/8 thick) on the top of the chip but the fan had to go on top of the cage facing downward. I know I know, it should blow the heat up but there was no room. It has now been running for about an hour now with no problems.

It should be noted that the other processor on this board is still using that blue foam. This chip does not get as hot but unit WILL shut down without any heatsink for this chip.

[dmitt25]

Re: Philips 42" Plasma 42PF7320

Awesome Dgtech! I'm glad this is working for you too!

PowerAmpFreak: The fans are still running, I didn't remove them, but I meant it sure doesn't feel like it's doing anything. It probably is, but you know, I guess I was expecting a little more "oomph" like heat BLOWING out the top instead of just making the back of the case feel hot. If I were to cut holes in the back of the case, I bet I would get much better results.

[Dgtech]

Re: Philips 42" Plasma 42PF7320

Just to add a little more to this thread in hopes that it helps someone else in the future. The fan I added was a 12 VDC fan about 1.5 inches square. This fan is attatched to the 12V supply on the card audio card. See pic.