Question about Planar PDP-42BK 42 in. Plasma HDTV
Okay, when I got the unit, it had the classic symptom of going on standby shortly after power-up and flashing the Green LED on the PSU board.
I bought the panel non-working from a local university without testing it, etc. When I tried to power it up at home, I got the green light, click from relay and nothing. No test screen. Using the symptoms I had, I checked FixYa to see the common C16, C19, C97 capacitor combo listed. I didn't open the set to see if the capacitors were bad. I just ordered new ones.
When those arrived, it was then that I opened the back and checked everything. To my amazement, the capacitors looked fine.
Powering the system on with the back taken off, I noticed the green LED on the PSU for the first time. It appeared to have a sequence of five short flashes, a long gap/flash where it stayed on and then three short flashes with another long gap/flash. I was unsure whether I counted the flashes right so I turned off the main power and turned it back on and maybe hit the soft power on button. I forget. In any event, I heard a fizzle and everything went dead. No lights (No music? Just anger! But I digress...) on the PSU and nothing at all. I unhooked everything and tested the 8A fuse at F1. It was blown so I decided to pull and test the capacitors.
When I pulled and tested each one with my meter, they were well within specification for capacitance. I don't have an ESR meter, but I do have access to one at work. My meter's capacitance test only charges with about 3VDC, for the record, so I don't know about leakage at the voltages seen inside the set.
I also looked at C103 for issues. It looked like there was crusty stuff on one lead that wasn't flux residue. I removed it and it also tested fine. Luckily, I had a replacement for that part on-hand.
I installed the new C16, C19, C97 and C103. Figuring the fuse was worth a look, I pulled it and saw it had a snap-together case. Opening the case, I saw the wire had melted and there was a little bit of black residue, but not what I see from really bad shorts. I soldered a 6.5A glass fuse to the posts of the original fuse and installed it. I figured it would just melt if the circuit was otherwise good.
I installed the power board and hooked everything back up. I plugged it in and hit the main power switch. It was fine with a green light on the PSU board until the relay clicked and the fuse blew quite energetically.
I started testing after the relay and found that R177 and R2 are both open while R3 measures 4.7ohm like it should. With R2 and R3 being in series, I believe it was a matter of R2 being weakest link.
So there are three things for the FixYa crowd to figure out:
1. Why does the relay turn on without the soft-switch being pressed?
2. Why would the lack of the resistors cause the fuse to blow?
3. Why did the resistors blow in the first place?
I have the power board schematic in front of me, but I seem to be missing something. If you want to take a crack at this and need a copy of the schematic, I can upload it and provide a link.
If you need more details or want me to do any tests, I can.
You must replace the drivers, the output/chopper transistors and use the correct type of R2/3 resistors otherwise you have a fire waiting to start.
Posted on Feb 26, 2017
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Posted on Jan 02, 2017
SOURCE: planar PDP42BK no picture
Check the 15v line that runs through all the boards, left, right and top.. If that has no power, then look on the ysus board (left one) there is a flyback reg (5pin) standard to-220 case surrouded by caps, it does dc to ac conversion, if you dont have the 15v output then the chip is bad. I just did 2 of these that had the same problem.
Posted on Nov 09, 2008
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Feb 18, 2018 | Planar PDP-42BK 42 in. Plasma HDTV
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