panasonic tx-p50s10b

[paulstef]

Re: panasonic tx-p50s10b

Measure again the voltage on the reference pin and STB_IN.

[tom66]

Re: panasonic tx-p50s10b

It is important not to connect the main board if you are fiddling with the reference until you are sure the PSU is working, this is to avoid a high standby voltage damaging the main. I have seen 12V come out of a 5V converter with failed feedback, this will obviously not do much for a board where most components will have an absolute maximum operating voltage of 5.5~6V.

[paulstef]

Re: panasonic tx-p50s10b

It is important not to connect the main board if you are fiddling with the reference until you are sure the PSU is working, this is to avoid a high standby voltage damaging the main. I have seen 12V come out of a 5V converter with failed feedback, this will obviously not do much for a board where most components will have an absolute maximum operating voltage of 5.5~6V.

I didn't even think about this but yes you're so right. There is also the uC on the PSU directly connected to STB_IN 5V... Better be careful.

[ronhayes]

Re: panasonic tx-p50s10b

Have checked the ref pin it is now 2.30v

[tom66]

Re: panasonic tx-p50s10b

What is output voltage?

[ronhayes]

Re: panasonic tx-p50s10b

3.80v

[tom66]

Re: panasonic tx-p50s10b

Ok, that is not good then, I think you might have to order a replacement TL431, preferably an exact replacement.

[paulstef]

Re: panasonic tx-p50s10b

The relationship almost hasn't changed... 4.73/2.8, or 3.8/2.3... Weird.

From here I think you would really need a scope, checking signal on cathode of the TL431 (should be non conducting at 2.3V), the optocoupler input and output, duty cycle of the controller IC...

There is only so much you can do with a multimeter.

What's the DC voltage on the cathode of the TL431 measured with your meter?

[ronhayes]

Re: panasonic tx-p50s10b

Maybe i am reading this all wrong !!
I have just measured volts on the IC551 (TL431C ) and what i am getting is pin 1 ref =2.30v pin 2 anode =0v pin3 cathode = 3.80v
Have not yet located my scope think i may have stored in the loft.

[paulstef]

Re: panasonic tx-p50s10b

Ok, but what voltage is STB_IN, the power supply for the uC?

[ronhayes]

Re: panasonic tx-p50s10b

Don't know if this will give you any clues but now i have installed this TL431C i get at pin 5 of P7 steady 4.80v with power button pressed in then slowly decreasing volts from 4.80v when power button released. pin 9 of p7 i get 4.58v then 0v when power button pressed. and pin 9 of p25 getting 4.80v steady with power button pressed then slowly decreasing volts from 4.80v when power button released.
This is with the plugs disconnected from the A board ?

[paulstef]

Re: panasonic tx-p50s10b

Pin5 of P7 and pin9 of P25 are the same signal, the switched STB voltage (5V). No need to measure both.

Anyway... Now we gained 70mV , up from 4.73V to 4.8V. No progress so far.

When the mainboard is connected, does the voltage at pin 5 of P7 remain ON even after releasing the push button?

[paulstef]

Re: panasonic tx-p50s10b

I think I would try to force the PSU on by activating the signals PANEL_Main_ON and F_STBY_ON.

You would need to connect the 4.8V to these signal inputs on P7 and P25. Without the A-board of course.

[ronhayes]

Re: panasonic tx-p50s10b

I get 4.80v at that point.

[tom66]

Re: panasonic tx-p50s10b

@ron, are we sure your multimeter is good?
Could you check against a known good reference? Or use another meter?

[ronhayes]

Re: panasonic tx-p50s10b

On pin 5 of p7 i get a steady 4.80v when power button pressed then when power button depressed it drops to less than 1v and slowly decreases from that 1v.
So would i link from pin 5 to pin 6 on p7 and from pin 5 of p7 to pin 11 on p25 or from pin 9 of p25 to pin 11.

[ronhayes]

Re: panasonic tx-p50s10b

Tom
I have a couple more cheaper type meters than my M92A one of them is a Hilix DT-830B
I have just put a new battery in it and tried that one and was getting 5,21v at pin 5 p7
(st-by 5v)
I just never thought to try another meter maybe it would be time to invest in a new multi meter,

[tom66]

Re: panasonic tx-p50s10b

Certainly, given that it appears to have put is on the proverbial "wild goose chase", as it appears nothing was wrong with the power supply! But, you live and you learn

[paulstef]

Re: panasonic tx-p50s10b

On pin 5 of p7 i get a steady 4.80v when power button pressed then when power button depressed it drops to less than 1v and slowly decreases from that 1v.
So would i link from pin 5 to pin 6 on p7 and from pin 5 of p7 to pin 11 on p25 or from pin 9 of p25 to pin 11.

Yes, and there is probably a sequence to turn them on.
Both signals go to the uC IC701 which will then activate RLY_MAIN and RLY_RUSH.

I'm assuming /RLY_MAIN turns on first and then /RLY_RUSH, therefore first will close relays K604 and K605 and then K602.

Is RF601 the white big resistor near the relays?

[paulstef]

Re: panasonic tx-p50s10b

You turn on one signal and observe what happens and then the other.And post the result here. Like which relay turned on when and which voltages you get on the different connectors.

Be careful :-)