Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

[smartjohn]

So I have been following the other threads here on troubleshooting the 50 inch Panasonic version. It looks to be the same or very similar to this 2009, 42 inch chassis.

So I pulled the ribbon cable and power cable (SC20 & SC2) off of the SC board and was able to get the 6 blinks which looks to be a bad SC board. Pulled the upper and lower buffers and removed the SC board and did some in circuit testing. Q452 (Q16452) an NPN power transistor was open in all directions on the 10 Meg scale. Looks like this would impact the FET driver signal in some way so I am guessing THIS IS A BAD THING! (The FETS appear to be OK in circuit) No shorts.

Part number for the NPN is 45G127 which is absolutely nonexistent!! No cross anywhere! I found a link to a Chinese distributor for the exact part but obviously no specs, however it was really cheap! So I went with my gut and found the cheapest T0-220 NPN power transistor at Radio Shack (TIP31 or 276-2017). I had to mount this with an insulator pad and screw as the original was self insulating. Put It all back, fired it up and got a "pulsating" red light for about 10 seconds then it went out. Never got picture or any screen action.

Now I'm back to 8 Blinks!! I am guessing I blew the NPN again. I am waiting for my parts dealer to try and cross it with his database tomorrow. I have about half a notion to pop in a 90W NPN which is Mo Power than the 40W i tried first!

Any thoughts would be appreciated! Cheers..

[tw2005]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

No offence but not wise guessing at what Q452 was. It's a 430V 45A, 200A max pulsed, N-channel IGBT (Insulated gate bipolar transistor) manufactured by Toshiba. Full part number GT45G127. If you still have that transistor it may be ok as there is a special way to test IGBT. Google testing igbt, bound to find some handy videos, that's what i did. Unfortunately you've most likely damaged other things now especially with change to SOS8.

[smartjohn]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

Well that was a hair brain move for sure! I need to verify the SOS8 vs SOS7 to make sure my last count was correct. It may just be back to the original 7. Thanks for the IGBT test suggestion. I'll update things tomorrow after these steps.

[smartjohn]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

OK, so I tested the IGBT which was removed and as suspected it appears to be ok. I used the 9 volt circuit here same as for testing MOSFETS. The VOM diode meter test I also found would not turn this IGBT on. I assume it needed more gate voltage to fire up! Replaced the IBGT and remounted SC, SD and SU boards. Sure enough, the SOS7 (seven blinks came back). This doesn't mean that I didn't damage the SC board, but only that the problem is still SC, SU or SD related.

I am a little confused on the board isolation test process, that is pulling the grounding screws and the removing the connectors between the SC and both buffer boards. The part I am confused about is plugging the jumper into SC50. Can you do this with upper or lower buffers connected independently, one at a time ? And still leave the other connecters plugged into the SC board (Vsus)? Will the panel actually fire up with this jumper or will it just let the rest of the set come on?

I checked the power connecter pins on both buffer boards for shorts. I did find that pin 2 of SU41 measures 13 ohms to the VF_GND ground tab on the SU board. I checked all pins on the SD board (SD42 and SD46) and measured infinite to the the VF_GND tab on the SD. Also infinite between all other pins on the each connector on the SD. Not looking good for the SU buffer board! There is no visible burning or scorched IC's on the SU board but I know that doesn't really mean anything.

I was getting ready to click BUY for another SU board on eBay but thought I'd pass this along first. Any thoughts? And many thanks for all the help here!!

[tw2005]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

I'd disconnect all power connectors at the su/sd and jumper sc50, turn on and see if power on normal or still blink code which could go sos6. if not I believe the set will prime the screen with just the ss board firing up. you may some glow or some kind of panel activity. do it long enough just to get a result don't run it for ages like this.

[tom66]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

With SU/SD missing I don't expect any kind of glow.

[tw2005]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

Glow, maybe the the wrong term but when I have done this on my 50" you get what you'd expect with a running SS and I did see some red streaks but it does say in the manual black no picture. I guess it was not full glowing but there was some activity.

[tom66]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

Strange, as the priming is generated entirely on the SC. The SS is necessary to get the proper priming wave, but it cannot work without the SC, or so I thought. May be different tech.

[tw2005]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

Strange, as the priming is generated entirely on the SC. The SS is necessary to get the proper priming wave, but it cannot work without the SC, or so I thought. May be different tech.

I always thought the x or SS primed and the SC/y produced the image? I have not studied in depth the working principles of a Plasma screen though.

Either way it's the SOS code I'm interested in but I have only done this bypass twice. Once on my 12th gen and once on the 13th P50V20A.

I can't recall the first result but It was the latter that I saw some activity which I did not expect. It was weird to look at but I shut it down as soon as it had passed it's checks. that was with no buffers connected.

[smartjohn]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

OK, all red glows aside, I disconnected all three power connectors from SU/SD and also removed the 4 VF_GND screws as Panasonic recommends, then jumpered SC50. I also monitored Vsus at SC2 on the SC board side. Power on Vsus went to 206 V for about 3 seconds then I heard the relay click out and it started bleeding down from 200. Back to SOS7 (seven blinks).

To further narrow things down, I isolated the SC board by pulling SC2 and SC20 on the SC board and SS33 on the SS board (I guess that would kill any red glow??). Anyhow, power up and relay clicks on for 3 seconds, click off, and now getting SOS6 (went from 7 to 6 blinks!)

So not looking good for the SC board?? !! I want to do component level on the SC, (cheap $'s!!) So for those of you who have been down that road, what are the most common failures on the SC board? My SC is part #TNPA4844. Thanks again for all input!!

Also, I am going to assume my buffers may be bad also... I can swear at one point I had both SD/SU isolated, SC50 jumpered and the fans came on and Vsus stayed up.. !! I shut it down in under the 30 seconds, but something else must have went south on the SC after this....not sure...

[smartjohn]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

After pulling the SC board, I found the FET Q660 is measuring in circuit, source to gate of 88 ohms (both directions). I will check the other FETs as well and may pull this out of circuit to test. Don't see anything here that would account for 88 ohms!

[tw2005]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

I generally check for shorts in cct but ideally best to test out cct. I've only ever done that in diode mode with a meter. No idea what resistance you'd see.
As for parts that fail, FETS, IGBT, diodes, FET driver ICs, voltage regulators, etc etc.

Not an easy fix. I'm currently attempting (experimenting) an SC board for the first time, parts yet to arrive but so far I'm up for FETS,IGBT,FET drivers, volatge reg, and a inverter logic ic.

Could end up being a big waste but I like the challenge.

Easiest way to get it going would be to source new boards. Definitely that low resistance looks bad on the SU but open on all SD sounds wrong too.

[smartjohn]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

On further checking, I see direct shorts across all pins of both IC724 and IC725 the 5V_F_A and 5V_F_B voltage regulators. Only problem is crossing this to a real part! The Panasonic part number is C0CBADC00072. It's a 5V SMD regulator but I have no clue how to cross this to a "standard" smd part. Any help on crossing is appreciated! http://www.flickr.com/photos/john_sm...7632918443848/

[tom66]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

My guess - something like 78M05 or 78L05.

[tw2005]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

78L05 SOT-89 I think?, Test it out of circuit though. I had the same issue but it was good once removed.

[smartjohn]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

What method are you using to desolder the smd components? These are so close I am afraid of unsoldering others pieces close by with a heat gun...

[tw2005]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

I just knew that would be the next question

I'm not set up well for smd either but the smd 5V reg I ran solder across the 3 pins and let the heat flow until I could carefully move it with tweezers. It's the center pin that needs to heat right underneath it as the back tab is gnd.

Not too hard but too much heat and the pads can lift. I used 40w iron.

Have you checked the larger 5V reg IC16771(IC771) at all?

[tw2005]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

IGBT data

[smartjohn]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

Have you checked the larger 5V reg IC16771(IC771) at all?

Vin to com is about 2.1 Ohms, Vout to com I am getting 6.3 ohms...These are in circuit. On my SC board (part #TNPA4844) IC771 looks to be the same size and same package as IC724 and IC725. Is it larger on yours? just curious.. Also, if your IC771 was defective, was it a dead short? Thanks...

[tw2005]

Re: Panasonic TC-P42G10 Plasma - Seven red blinks Dead No power

My bad, I'm running off the schematic. I'm comparing this to TNPA5081 but there are some similarities. IC771 on mine is the 78M05 and much larger and this was dead short.

The resistance you measure is interesting as that IC connects to a FET driver IC and 2 inverter IC as well.

Seriously, this will be no walk in the park.

I'm thinking IC16501 will be bad and possibly IC16464,465. It's the SMD inverter ICs that have given me trouble removing without some track damage.

I can't think of any other way than to remove items to isolate the failed parts unless someone else has ideas.