Hey, Everyone. I'm a total newbie to electronics repair, but I do own a decent digital multimeter. I need some help getting a Panasonic TC-P50G25 back up and running. I've detailed my troubleshooting process below and I'm hoping to any general advice as you all may have, and get some answers to the specific questions at the end of the post. Thanks in advance! Sorry if the level of detail is excessive.
Problem: In-laws were using the TV one night. Father in-law turned it off, mother in-law wanted to keep watching and tried to turn it on, but it would not turn on. Apparently, there was initially a 4-blink code, but later (after some unplugging and plugging back in to different outlets, etc.) a 10-blink code.
Troubleshooting: TV was left unplugged for >12 hours and power button held down in order to discharge/reset. This did nothing. Still 10 blink code when powered on.
That's where I came in. After googling around a bit I popped off the back cover, dusted the boards with compressed air, and visually inspected all of the capacitors for bulging/leaking. I found no defects.
I read through various threads on this site and found the “2010 – FHD Plasma TV Troubleshooting Handbook,” which is a fairly comprehensive handbook released by Panasonic for technicians working on G20 and G25 series TVs (PDF is attached to this post).
Below are the results of working through the troubleshooting guide.
PDF Slide 8 – Quick procedure to check for short or low resistance condition of the Vsus, Vda, and P15V lines
The TV has been disconnected for several days, so I skipped the step where residual charge is removed by grounding through a 500 ohms resistor. I measured the resistances indicated in step three of slide 8 (black lead on chassis and red lead on the indicated pin on the P-board) and obtained the following:
P11/White (Pin1, Vsus) --> 429 Ohm
P11/Brown (Pin 4, P15V) --> 29.2 Ohm.
P35/White (Pin 1, Vda) --> Starts out at around 15 MOhm and drifts downward (reached 5 MOhm after a minute or two and continued to decrease)
Based on the above readings, it appears that there is both a P15V and a Vsus short, or partial short.
Slide 12 – Detailed troubleshooting procedure for shorted Vsus.
Step 1: Unplug connectors P2 and P11 on P-board and measure resistance between P2 (pin 1) and ground (Chassis).
Result: 15 MOhm and dropping. No short.
Step 2: Measure the resistance between pin1 of connector SC2 on the SC board and ground (Chassis).
Result: 432 Ohm. Short.
Step 3: Measure the resistance between connector SS11 (pin1) on the SS board and ground (Chassis).
Result: 4 MOhm. No Short.
Final Result: Replace SC Board.
Slide 13 – Detailed troubleshooting procedure for shorted P15V
Step 1: Unplug connectors P6 and P11 on the P-board and measure resistance between P6 (pin1) and ground (Chassis).
Result: 7.77 kOhm. No short.
Step 2: Reconnect P11 and measure the resistance between P6 (pin1) and ground (Chassis).
Result: 2.64 kOhm. No short.
Step 3: Disconnect SC20 on the SC board and reconnect P6. Measure the resistance between P6 (pin1) and ground (Chassis).
Result: 7.8 kOhm. No short.
Final Result: Replace SC board.
Ok, so it looks like the SC board is bad. But….just to be sure, I followed the advice of TW2005 on this thread and checked the following IGBTs:
Q402 --> G-E = 6.3 Ohms; E-C = Short; G-C = 7 Ohms
Q403 --> G-E = Short; E-C = Short; G-C = Short
Q421 --> G-E = 5 Ohms; E-C = Short; G-C = 5 Ohms
Q422 --> G-E = 7.2 Ohms; E-C = Short; G-C = 7.2 Ohms
Q661 --> G-E = 9.5 Ohms; E-C = Short; G-C = 9.5 Ohms
Q441 --> G-E = 47 kOhms; E-C = 367 kOhm; G-C = 47 kOhms
Now, I know that I need to replace the SC board, but I read in this thread that it is important to also test the SD and SU buffer boards before fitting a new, or refurbished, SC board. Once again turning to the Panasonic Troubleshooting guide (attached), I went through the following steps.
Slide 43 – Vfo, VSCN-F, & 5V_F Resistance Measurements (SU-SD boards)
Step 1: Remove the 4 VFG screws from the SU and SD boards…check!
Step 2: Disconnect SC41, SC42, and SC46 from the SC board. Also, remove the ribbon cable between the SU and SD boards (SU11/SD11).
Step 3: Using the VF-Ground as reference, measure the Vfo, VSCN-F, and 5v-F resistances on the SU and SD boards individually (here I used the Chassis as ground since the point highlighted in the image on Slide 44 of the troubleshooting guide does not appear to be a ground).
SU41 (pin2, TPSU15, 2.2M) --> 5.77MOhm
SU41 (pin4, TPSU16, 221K) --> 221KOhm
SU41 (pin8, TPSU17, 5.7M) --> No Response
SD42 (pin1, TPSD29, 2.2M) --> 6.14 MOhm
SD42 (pin2, TPSD28, 221K) --> 221K
SD42 (pin6, TPSD26, 5.7M) --> 15 MOhm (Rising, climbs over 20 MOhm)
I'm confused by a couple of things here.
First, it appears as though the troubleshooting guide has reversed the expected resistances for VFO and 5V_F. Would you all agree?
Second, when I test TPSU17 (both on the test point and on the actual pin) I get NO RESPONSE from the multimeter…nothing. In other cases (for instance when I indicated short above for various IGBTs) the voltmeter will go from reading “0.L” when not in contact with anything, to reading 000.1 Ohm when the two leads are touched together, or when reading an actual short. Why does this pin not respond at all? Also, why is the reading for the same line on the other board so high?
I repeated the above measurements after jumping pin1 and pin2 of SC50 with an alligator clip. Readings were identical to those without the jump.
Have I approached this problem correctly?
Do these overall results indicate that all three boards (SC, SD, and SU) are bad?
If so, what is the best way to fix/replace these boards?
Board , Part#
SC, TNPA5081AF (TXNSC1LPUU)
SD, TNPA5091
SU, TNPA5090
I've seen panel board repair at moduslinks for $220.20
I also see a trade in on eBay for just the SC-board for $137 plus $16 shipping. They (oleg_yj) say that if you send in the buffer boards, they will test them for free, but will charge for repair or replacement and do not list the price of the buffer boards.
Problem: In-laws were using the TV one night. Father in-law turned it off, mother in-law wanted to keep watching and tried to turn it on, but it would not turn on. Apparently, there was initially a 4-blink code, but later (after some unplugging and plugging back in to different outlets, etc.) a 10-blink code.
Troubleshooting: TV was left unplugged for >12 hours and power button held down in order to discharge/reset. This did nothing. Still 10 blink code when powered on.
That's where I came in. After googling around a bit I popped off the back cover, dusted the boards with compressed air, and visually inspected all of the capacitors for bulging/leaking. I found no defects.
I read through various threads on this site and found the “2010 – FHD Plasma TV Troubleshooting Handbook,” which is a fairly comprehensive handbook released by Panasonic for technicians working on G20 and G25 series TVs (PDF is attached to this post).
Below are the results of working through the troubleshooting guide.
PDF Slide 8 – Quick procedure to check for short or low resistance condition of the Vsus, Vda, and P15V lines
The TV has been disconnected for several days, so I skipped the step where residual charge is removed by grounding through a 500 ohms resistor. I measured the resistances indicated in step three of slide 8 (black lead on chassis and red lead on the indicated pin on the P-board) and obtained the following:
P11/White (Pin1, Vsus) --> 429 Ohm
P11/Brown (Pin 4, P15V) --> 29.2 Ohm.
P35/White (Pin 1, Vda) --> Starts out at around 15 MOhm and drifts downward (reached 5 MOhm after a minute or two and continued to decrease)
Based on the above readings, it appears that there is both a P15V and a Vsus short, or partial short.
Slide 12 – Detailed troubleshooting procedure for shorted Vsus.
Step 1: Unplug connectors P2 and P11 on P-board and measure resistance between P2 (pin 1) and ground (Chassis).
Result: 15 MOhm and dropping. No short.
Step 2: Measure the resistance between pin1 of connector SC2 on the SC board and ground (Chassis).
Result: 432 Ohm. Short.
Step 3: Measure the resistance between connector SS11 (pin1) on the SS board and ground (Chassis).
Result: 4 MOhm. No Short.
Final Result: Replace SC Board.
Slide 13 – Detailed troubleshooting procedure for shorted P15V
Step 1: Unplug connectors P6 and P11 on the P-board and measure resistance between P6 (pin1) and ground (Chassis).
Result: 7.77 kOhm. No short.
Step 2: Reconnect P11 and measure the resistance between P6 (pin1) and ground (Chassis).
Result: 2.64 kOhm. No short.
Step 3: Disconnect SC20 on the SC board and reconnect P6. Measure the resistance between P6 (pin1) and ground (Chassis).
Result: 7.8 kOhm. No short.
Final Result: Replace SC board.
Ok, so it looks like the SC board is bad. But….just to be sure, I followed the advice of TW2005 on this thread and checked the following IGBTs:
Q402 --> G-E = 6.3 Ohms; E-C = Short; G-C = 7 Ohms
Q403 --> G-E = Short; E-C = Short; G-C = Short
Q421 --> G-E = 5 Ohms; E-C = Short; G-C = 5 Ohms
Q422 --> G-E = 7.2 Ohms; E-C = Short; G-C = 7.2 Ohms
Q661 --> G-E = 9.5 Ohms; E-C = Short; G-C = 9.5 Ohms
Q441 --> G-E = 47 kOhms; E-C = 367 kOhm; G-C = 47 kOhms
Now, I know that I need to replace the SC board, but I read in this thread that it is important to also test the SD and SU buffer boards before fitting a new, or refurbished, SC board. Once again turning to the Panasonic Troubleshooting guide (attached), I went through the following steps.
Slide 43 – Vfo, VSCN-F, & 5V_F Resistance Measurements (SU-SD boards)
Step 1: Remove the 4 VFG screws from the SU and SD boards…check!
Step 2: Disconnect SC41, SC42, and SC46 from the SC board. Also, remove the ribbon cable between the SU and SD boards (SU11/SD11).
Step 3: Using the VF-Ground as reference, measure the Vfo, VSCN-F, and 5v-F resistances on the SU and SD boards individually (here I used the Chassis as ground since the point highlighted in the image on Slide 44 of the troubleshooting guide does not appear to be a ground).
SU41 (pin2, TPSU15, 2.2M) --> 5.77MOhm
SU41 (pin4, TPSU16, 221K) --> 221KOhm
SU41 (pin8, TPSU17, 5.7M) --> No Response
SD42 (pin1, TPSD29, 2.2M) --> 6.14 MOhm
SD42 (pin2, TPSD28, 221K) --> 221K
SD42 (pin6, TPSD26, 5.7M) --> 15 MOhm (Rising, climbs over 20 MOhm)
I'm confused by a couple of things here.
First, it appears as though the troubleshooting guide has reversed the expected resistances for VFO and 5V_F. Would you all agree?
Second, when I test TPSU17 (both on the test point and on the actual pin) I get NO RESPONSE from the multimeter…nothing. In other cases (for instance when I indicated short above for various IGBTs) the voltmeter will go from reading “0.L” when not in contact with anything, to reading 000.1 Ohm when the two leads are touched together, or when reading an actual short. Why does this pin not respond at all? Also, why is the reading for the same line on the other board so high?
I repeated the above measurements after jumping pin1 and pin2 of SC50 with an alligator clip. Readings were identical to those without the jump.
Have I approached this problem correctly?
Do these overall results indicate that all three boards (SC, SD, and SU) are bad?
If so, what is the best way to fix/replace these boards?
Board , Part#
SC, TNPA5081AF (TXNSC1LPUU)
SD, TNPA5091
SU, TNPA5090
I've seen panel board repair at moduslinks for $220.20
I also see a trade in on eBay for just the SC-board for $137 plus $16 shipping. They (oleg_yj) say that if you send in the buffer boards, they will test them for free, but will charge for repair or replacement and do not list the price of the buffer boards.
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