Panasonic TH-42PZ77U SC board repair 7 blinks

[tom66]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

You should test between the tab and each of the two pins.
The tab is drain, one pin is gate, one pin is source.

The same fet on my board failed on as the AVSForum one, so I would suspect that one.

[johnboy1313]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

Since I have so little experience doing this, I decided to test all seven with the red on the lifted leg and the black on base. In this configuration I got
1=541
2=541
3=013
4=541
5=541
6=290
7=290

[tom66]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

013 --- you found the dead one.

[johnboy1313]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

You should test between the tab and each of the two pins.
The tab is drain, one pin is gate, one pin is source.

The same fet on my board failed on as the AVSForum one, so I would suspect that one.

Ok, I'll get the other leg too. Does it need to be lifted from the board too?

[johnboy1313]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

013 --- you found the dead one.

Cool. Do you think I should keep testing the rest of the transistors? Do you see a problem with #'s 6 and 7 being so different than the other 4?

[tom66]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

#3 is definitely bad. If you cut both lower pins, try the TV and see if it works. Then replace the fet.

[johnboy1313]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

So, I kinda got ahead of myself and turned the set on before connecting SC2 and SC20. I shut it back off and unplugged it from the wall. How long should I wait before trying to connect those plugs? Is there a method to discharging the unit?

[randtek]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

Usually a few minutes is long enough. I have been told that pressing and holding the power button for 10 seconds will help discharge too. I don't know if it really does or not.

[tom66]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

Check the Vsus voltage. If it's under 20V I'd say it's fine. It'll decay while the TV is off. You may get a tiny spark.

[johnboy1313]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

It came on but the screen seems to be split horizontally down the middle. Below the line, the black part of the screen is very black. Above the line, the black part is kinda grey. The menu is clear on the top and bottom. I disconnected the SD board from the panel before I realized I didn't need to. Is there an adjustment for this? Do i need to play with the ribbon connections again? Have you ever seen anything like this? There is nothing wrong with the picture anywhere on the screen, just a difference in the top half and bottom half.

[johnboy1313]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

Never mind this post. I thought I had it fixed but I was wrong. It's still darker on the bottom.

[johnboy1313]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

So, the darkness was caused by me. When I originally pulled the SD board, I didn't see the middle flex connector. When the board slid out of the SC, it pulled the plastic housing off of the pins on the SD board. I carefully put the housing back on but damaged the top most pin doing so. I then pulled the pin off of the board when I was trying to straighten it. I know, I can be a real klutz sometimes. Long story short, I got the pin straightened out and reattached to the board, but it showed considerably more resistance from the pin to the trace on the circuit board than the rest of the pins on that clip did to their own traces. I ran a jumper from the pin to the back of the board where the trace came through. Now when measured from the back of the board to the pin on the front, I saw 1.4 ohms, just like all of the other pins. I was really proud of my fix. Well, just now as I was taking these pics, I decided to test the resistance of the top pin on the SU board compared to its trace. It was considerably more than 1.4 ohms, so much that I got an overload with the meter set at 200 ohms. I cut my jumper and powered on the set and bingo, no more darkness. I guess I'm lucky I didn't burn anything up.

Now I just need to figure out where to find a 5N2307 transistor, how to remove the bad transistor without damaging the board, and how hard it is to install the new one.

[tom66]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

Yeah, I damaged that connector when I fixed the TH-42PZ70BA too, so I used a bit of (relatively weak) glue to secure it.

[johnboy1313]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

The part number is B1DFKM000002 or 5N2307. Here is thread from AVS Forum with some info for you. http://www.avsforum.com/t/1001318/ma...#post_17876879

I ordered two Panasonic B1DFKM000002 this morning. $15.42 total including shipping. Now, how hard is it to remove that thing from the board? Is the entire back of the transistor soldered down? If so, I doubt my little 30W iron will get it out.

EDIT, picture below stolen from link above.

[tom66]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

Yes, entire back is soldered.

Just apply lots and lots of heat, and push it slowly and carefully off the pad. Be very careful not to damage the pad.

[johnboy1313]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

What's the trick to removing this FET? I've got a 100w, a 140w, and a monster 180w soldering gun and I can't seem to get this thing hot enough to move. Do I just put the tip of the gun on the thing and hold it until it's hot enough?

[tom66]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

Lift the two pins, apply heat to the tab, and push on it. It will come off after some time. 100W max. 140/180W could damage PCB.

[johnboy1313]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

Got it. That's the new one. Third from the top.

[tom66]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

Great. Does TV work ?

[johnboy1313]

Re: Panasonic TH-42PZ77U SC board repair 7 blinks

Haven't got that far yet. It's dinner time here.