Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

[nintari]

Found another project to work on and learn from

Panasonic EDTV Model TH-42PW4UZ

Symptoms: Unit powers on, you hear a relay click, green LED on front indicates Unit is on, nothing happens on screen at all....? No light no image, no distortion... nothing. I left the unit on for a while and I think it went in to standby mode since there were no inputs attached. The light went from green to red, stayed red steady, blinked 6 times, then steady on the last. I don't think this is an error code since it took a long time for it to do this.

I am in the process of looking for service manuals now, tip suggestions and etc.

I know this is an EDTV but for me it is more about the experience than the unit itself.

I have attached a pic of the unit with the back off.


I would have assumed some sort of error lights would have given some indication of what is going on, but no luck.

I did notice there were LEDs on two of the boards (I think SC or SS board and power board) neither of which were lit up (could either be dead LEDs or pointing toward the problem.

Physical inspection revealed no cracks in the glass as of yet.

[nintari]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

dang it forgot to hit subscribe....

[tom66]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

Check Vsus & Vda on PSU.

[nintari]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

just got hold of the service manual and am reading through it now to get some ideas and thoughts.

Sadly I don't have this set here with me at work so I have to wait until tonight to check in to it.

Thanks for the tip I will look in to that.

Just now realized I'm going to have to pickup a decent multimeter. I can't keep borrowing the one from work lol. mine was an older fluke I picked up from a yard sale but it has long been dead.

[nintari]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

Finally home and have a bit of time to poke around with my new fluke 177

Let's do this! lol

[nintari]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

As requested

Vsus 170.6
Vda 67.4

Looking through service manual now for other points / steps to check

[tom66]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

In a dark room can you see the screen lit up or not?

What is panel rating? 170V is very low Vsus for Panasonic. Typically 205~210V. However this is an older plasma panel, so it might be normal.

[nintari]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

Dark room no life

170v +/- 1v is normal on service manual

[tom66]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

OK, can I have a clear shot of the SC board (left hand plasma driver)

[nintari]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

Just were I was moving to next led on sc board is dead. Not much info on testing the sc board so far but still looking gimme a minute to get pic of sc board

[nintari]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

sc board

I can get some closeups if needed or upload the service manual I have somewhere

[tom66]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

6 blinks: Suspect ERC circuit -- If one of those is a 2SK2993/2995 SMD fet you probably found the problem, it's a very common issue with their HDTV sets too.

Check those SMD FETs for shorts.

[nintari]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

Yes getting odd readings from a few of them

In particular the one pictured in the lower left (picture rotated on upload) is reading 159.9v out while all the others were at 13.9v.... but now none of them are reading out.... not sure if I accidentally shorted something or if something overheated further lol

[tom66]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

You should be measuring with power off.
They are all in parallel and one usually likes to short.

[retiredcaps]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

mine was an older fluke I picked up from a yard sale but it has long been dead.

Tom66 is the expert in plasma troubleshooting. If you want to try and fix your old Fluke, start a new thread and I will try to give you some suggestions.

Post it in the "Test Equipment Usage, Techniques, and Reviews" section.

[nintari]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

Hmmm... tried looking up how to test this properly and not sure I am doing it right

meer on diode test mode

Between gate and source I get ol on all

Red on source and black on drain I get a reading of 454 and reading how to test from there seems to be throwing me off....
edit:

sorry tablet was dying lol

fluke was thown out years ago. I finally got tired of seeing wasted electronic devices and started tinkering with them and trying to learn what I can to repair them. since it benefits my job my boss bought me the new multimeter today

[nintari]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

and sorry for any misunderstandings or blatant stupidity thats why I am doing this on dead sets I get for free... to learn what I can (especially from mistakes)

[retiredcaps]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

Between gate and source I get ol on all

Red on source and black on drain I get a reading of 454 and reading how to test from there seems to be throwing me off....

In diode test mode, one reading should be 0L and other should show something between 0.3 to 0.7V.

A shorted transistor would show very close to 0.0V.

When I test components for a short, I use plain simple resistance mode. Any reading under 30 ohms suggests the component is shorted and it needs to be desoldered and verified out of circuit.

fluke was thown out years ago.

Hmm, too bad. If you come acros anymore dead or non working ones, send me a PM.

[nintari]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

I typically find lots of items being thrown away or sold dirt cheap, and I always wanted in the past to take anything I could get just to open it up and poke around... but I never did and regret so many items I have passed up. Combine that with things I have had in the past that have died and it depresses me to think about it all.

Really any TVs or items I get for free and end up fixing I'll more than likely donate to other people that otherwise couldn't afford one. There are quite a few people around here like that.

Of course if I get something really good it might replace something I have that isn't as good

I have to make arrangements to go pickup a 50" panasonic plasma TV sometime soon, hopefully it will be this week.

[nintari]

Re: Project 2: Panasonic TH-42PW4UZ green light on, nothing on screen

Spent time last night and this morning trying to learn more about these FETs and testing

I went a bit further down and found the following (pic attached and components circled in red)

again still trying to learn so I may me measuring wrong

Mitsubishi MOSFET FS7VS 14a

The two circled ones with meter in Diode test mode

Red on source black on gate I get a reading of 653 on the meter, the others not circled I get OL on meter

would that indicate these are possibly shorted?