Re: Panasonic TC-P50C2
Second A board arrived today from Baltimore. After allowing a couple of hours for it to warm up to room temperature, I installed it in the TV. Connected the DVM to measure the voltage “MID” on connector SS3 on the SS board, held my breath, and hit the power-on button. Oh no, DVM reads 15.11 volts just like before. However, about half a second later, the reading changed to 120V. Problem solved.
I am a little disappointed with the guy that sold me the first A board. He committed one of the cardinal sins of electronics ( and other disciplines...
Mark W
Member
Last Activity: 02-26-2020, 04:01 PM
Joined: 11-12-2013
Location: Frederick Maryland
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Re: Panasonic TC-P50C2
Just about sure (99.9%) that the A board is bad. Talked to the guy that sold it to me and he is willing to refund my money if I return the board. He got it out of a TV with a cracked screen but I think maybe because of the craked screen, he never tried to power it up and assumed that the cards were good. I should have asked him about that but didn't think of it at the time.
Meanwhile, I have purchased a second A board which should arrive in a day or two. Hope this one works.
Mark W
418Leave a comment:
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Re: Panasonic TC-P50C2
Back again. Have not given up on this TV. Taking a closer look at the schematic, it looks like a short between MID and +15V would result in smoke when Q16001 and Q16002 on the SS card turn on and drive MID to Vsus.
Since there was no smoke, I have assumed that Q16001 and Q16002 are not being turned on. The drive signal for these two transistors (AA_UMH) originates on the A board and is buffered on the C2 and SS boards. The input to buffer IC17203 on the C2 card measures 680 ohms to gnd on all three buffered signals. This agrees with the value...Leave a comment:
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Re: Panasonic TC-P50C2
Here is a picture showing MID on the top trace and +15V on the bottom.
Sensitivity is 5V/div for both traces. Time base is 1 sec/div
Sure looks like MID is being clamped to the +15V....Leave a comment:
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Re: Panasonic TC-P50C2
Just measured 23.18k with + lead on +15 and -lead on MID
Reversing the leads gives 71.4k.
Readings are repeatable and take a couple of seconds to settle to the
final value. Acts like capacitors charging. I suspect it is a FET or IGBT
that is causing the problem. May learn more after I look with the scope.Leave a comment:
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Re: Panasonic TC-P50C2
tom,
Did not see your post about Vscan being OK. Thanks, that is one less gremlin to chase.
This is first forum I have ever used so am still learning how to navigate. Your post was first one on page 2 and I did not realize that page 1 was full.Leave a comment:
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Re: Panasonic TC-P50C2
Update - now back to 6 blinks.
You're not going to beleive this but I had forgotten where the LED is located. The TV is lying face down on my bed so that I have easy access to all of the boards. Problem is that this faces the power switch and the LED down into the blanket on top of the bed. I have been using a stick to poke under the edge of the TV to operate the switch and was then looking at the back of the switch to see the LED which is ACTUALLY located a few inches to the left. Yes I know it seems impossible that I could count six blinks...Leave a comment:
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Re: Panasonic TC-P50C2
Measured MID voltage and got 15.xx volts. This is same voltage I measured
when I first began this adventure.
Vsus is still 190V. What has changed since I disconnected SU/SD is that I
get no blinks and relays seem to stay operated for a few seconds longer than
before.
I did get the six blinks two times on power up just after I disconnected SU/SD (forgot to jumper SC50). After that no blinks on power up with jumper on SC50.Leave a comment:
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Re: Panasonic TC-P50C2
Tried to measure VSCAN. Went to -42.7 volts but got zero blinks. Tried
several times and got zero blinks. Then realized that I had not jumpered SC50.
Put a jumper on and tried again. Still get -42.78 volts and no blinks.
Did I break something?Leave a comment:
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Re: Panasonic TC-P50C2
Disconnected SD/DU Powered ON Now get 6 blinks Back to the schematic.
Hope maybe if I can fix the 6 blinks, the 7 will go away.
If this was easy, everyone would do it.Leave a comment:
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Re: Panasonic TC-P50C2
tom,
The ones between the SC and SD/SU. So easy I am embarassed that I had to ask. A gentle longitudinal squeeze and they open right up. I had tried poking and prying before and could not figure it out. Tried again last night
and got it.
Don't think I need to disconnect the panel. Have not tried to jumper SC50 and power up but may do that later today.
thanksLeave a comment:
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Re: Panasonic TC-P50C2
How do you release the connectors? I don't want to break them.Leave a comment:
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Re: Panasonic TC-P50C2
tom66,
I see that you have a link to the service manual. If you search the manual for “IC16471”, this will get you to the circuit that I am trying to understand. If OPTO PC16480 is off, this will allow the signal MAIN_STOP0 to be pulled high by R16475 which then goes
through buffer IC16561 and sets SOS7_SC2. Q16876 turning off would also set SOS7_SC2. I would like to understand what can cause either or both of these conditions.
tw2005,
I have not tried to isolate the SU and SD cards. I am a little apprehensive...Leave a comment:
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Re: Panasonic TC-P50C2
Please ignore my comments about the opto not doing anything. I was
looking at IC16471 and assumed that it was an opto. Failed to notice
the words SHUNT REGULATOR. If I can identify that part and get a data
sheet, the circuit may make some sense.
Hope you both can bear with me. I make a lot of mistakes.
Mark WLeave a comment:
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Re: Panasonic TC-P50C2
tom,
I was hoping you might find this thread and offer some suggestions.
The statement in my first post that the "mid" voltage was setting the
SOS7 was incorrect. I was having trouble reading the schematic. I now
think the circuity around the opto is responsible for the SOS7 but have
not yet figured out how it is supposed to work.
In this circuit, the emitter of the transistor is not connected to anything. The schematic has the word "REFERENCE" written over the transistor end of...Leave a comment:
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Re: Panasonic TC-P50C2
Made the following measurements today.
Vsus on SC2-1 and SS11-1 >3 meg ohms to gnd (can see cap charging)
15V on S11-4 > 3 meg ohms
15V on SC20 pins 1 & 2 > 3 meg ohms
P5V on SC20-30 4.45K
Voltages before it shuts down are
Vsus = 190V
15V = 15.46V
P5V = 4.98V
Having spent some time pulling my hair out trying to follow the schematic
for the SC card, it looks to me like the opto coupler PC16480 may be the
souce of the SOS7_SC2 signal via...Leave a comment:
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Re: Panasonic TC-P50C2
Thanks for the reply.
VSUS gets to about 190V before relays click off.
IGBTs all check ok with ohmmeter.
A board is TNPH0831 3A
SC TNPA5063 2
SS TNPA5072 1
What are "buffers" ?
What is purpose of SC50 ? Schematic says "factory use only".Leave a comment:
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Panasonic TC-P50C2
Panasonic TC-P50C2 MC127H36U13 stopped working. Would not turn on. No LED no relay click. Bought replacement “A” board on e-bay and installed it. Now hear relays click but then get seven LED blinks.
Service manual says this is SC or SS board problem. Green LED on SC lights for a couple of seconds then goes out when I hear the relays drop.
Voltage on signal “MID” which connects to SS card only gets to +15V and
should be between 65 and 147 volts. This sets error SOS7. Can not see a short from +15 to MID using ohm meter.
Used oscilloscope... -
Re: New Members - please post your introductions here
Hi,
I am new member looking for help fixing my Panasonic plasma TV. Chassis number is MC127H36U13. Will give details after I figure out how to use the
Forum. Have never joined one before.
Mark WLeave a comment:
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