panasonic tx-p50s10b

[ronhayes]

Hi All
After following instructions on flow chart Kindly supplied by TW2005 no relays clicking disconnected plugs as instructed and checked volts at pins on plugs p7 and a6 it advices to replace P board.
What i was wandering was there any known faults on this board that may now have been discovered or do you have to replace these boards still ?

Ronhayes
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[Alastair E]

Re: panasonic tx-p50s10b

Ive had the Va/Vs switching MOSFETS fail S/C taking out the fuse....

[ronhayes]

Re: panasonic tx-p50s10b

I have checked the fuses on the P board all seem ok.

[Alastair E]

Re: panasonic tx-p50s10b

Only thing to do is the usual fault-find process--just like any other PSU. Check Tom's site for schematics of set.....

[ronhayes]

Re: panasonic tx-p50s10b

Hi Alastair E
In your last response to me you said to check Tom's site for schematics of set. Do you mean Tom 66 and if so do you have link to his site ? And also should i contact him first before going to his site? and ask for his permission to visit his site.
Regards Ron

[vinceroger69]

Re: panasonic tx-p50s10b

http://www.toms-service-manuals.com/

[ronhayes]

Re: panasonic tx-p50s10b

Thank you vinceroger69.

[tom66]

Re: panasonic tx-p50s10b

No permission required
If all fuses are good & relays not clicking, check 5V standby.
If absent = concentrate on PSU.
If not absent = check A board signals, could be bad A board not sending power on signal, etc.

[ronhayes]

Re: panasonic tx-p50s10b

Hi Tom
Thank you for your input .
I have checked the 5v stby on pin 5 of p7 on p board and i get 4.73 at switch on so should i assume that the fault is with the A board?
Ron

[tom66]

Re: panasonic tx-p50s10b

It would be the place I would concentrate on, though 4.73V is quite low for a 5V rail...

[paulstef]

Re: panasonic tx-p50s10b

Hi Tom
Thank you for your input .
I have checked the 5v stby on pin 5 of p7 on p board and i get 4.73 at switch on so should i assume that the fault is with the A board?
Ron

Please post a photograph of the the area with the two connectors to the right. There should be a description of each pin printed on top or bottom of the PCB.

Is this your chassis? http://elektrotanya.com/panasonic_tc.../download.html

[paulstef]

Re: panasonic tx-p50s10b

In my previous post there is a link to document containing the schematic of the PSU as well. You can't have it any better than that. It's supposed to be the ETX2MM747MFG.
Can you confirm?

I attached two pictures of the connectors where you should measure the signals.

Measure all the signals on P7 and P25 while the set is in standby and while you try to turn it on. It's important to post any changes that the signals show, like first it's 0V, then after 2sec it's 5V etc.

[ronhayes]

Re: panasonic tx-p50s10b

Hi Paul
Yes on the P board it is marked ETX2MM747MF and large letter G on white label just at the end of board number.
I have added pictures as you asked but no description on boards as you can see.

[ronhayes]

Re: panasonic tx-p50s10b

Hi Paulstef
I see what you are advising but when the P board is connected it is not possible to take measurements from these points as the solder point is under the board ( I would need to solder extension pins on so i could measure in situ) would that be the way you would go?
or take the measurements on the A board as it is possible on that board but would have to track each wire to each pin ?
Also in the schematics it quotes to A6 and A25 but on my A board the plugs are marked up A7 and A25 but i assume A7 is A6?

[paulstef]

Re: panasonic tx-p50s10b

You should be able to measure directly on the connector from above, where the wire was crimped to the terminal.

If your probe doesn't enter use an alligator clip with a rigid wire attached to it.

[ronhayes]

Re: panasonic tx-p50s10b

I have measured volts on connectors P 7 and P 25 volts as follows:-
P 7 = PINS 1,2,3,4,6,7,10,11= 0V STBY press button wait 2 seconds or more still 0v pin 5 STBY 0v press button 4.73v pin 8 0v STBY press button 2.84v for one second then 0v pin 9 STBY 0v press button 4.70v.
P 25 = pins 1,2,3,4,5,6,7,8,10,11,12,13 =0V STBY press button wait 2 seconds still 0v pin 9 = 0v STBY press button 4.73v

[ronhayes]

Re: panasonic tx-p50s10b

Would this point to the A board or the P board ?

[paulstef]

Re: panasonic tx-p50s10b

There are only two input signals from the mainboard, P7/pin6 (F_STBY_ON) and P25/pin11 (PANEL_Main_ON).

The microcontroller obviously runs since the standby on button works, presumably connected to P34, right?
It enables then STBY5V on P25/pin9 and P7/pin5. The mainboard is then supposed to send PANEL_Main_ON and F_STBY_ON, which it doesn't.

It looks more like a A-board fault but I would still verify if the 5V standby voltage (or VDD at pin6 of IC701) is really supposed to be 4.73V.
For this you need to tell us the values of R556 and R555 next to IC551. This determines the output voltage.

If you have a scope measure also voltage ripple at this point.

If the P-board is ok you would probably be able to start it manually disconnecting P25 and P7 from the A-board and manually activating PANEL_Main_ON and F_STBY_ON.
I need to check in which sequence that's supposed to happen.

[paulstef]

Re: panasonic tx-p50s10b

Does the power LED blink or is it always off?

[tom66]

Re: panasonic tx-p50s10b

I still think the 4.73V needs investigation - it is too low for a 5V rail, and could potentially trigger some kind of under-voltage lock-out (unlikely, but worth considering)