Panasonic TC-42PX14 Zener Diode

[mr.sky]

Re: Panasonic TC-42PX14 Zener Diode

Yes, the standby power supply will start running the minute the power plug is plugged into the outlet. All TVs need standby power supply to run the processor on the main board and the remote receiver so it will be ready to take command to turn on the rest of the power supplies from the power switch or from the remote control. This is how TV uses less power when it is not on.
Are you getting any DC at IC502 PIN2 VCC input pin? and the voltage reading on the rest of the pins of IC502.
Since you are getting the 5V, that means the transformer is working.

That was the first IC I took voltage pin 2 was 21.3v first reading, second
reading 19.5v, after that got no reading, meter readings not stable.
Also T200 pin 18 at first reading 21.1v. I will try again tomorrow, once
I get a new 9v battery

[budm]

Re: Panasonic TC-42PX14 Zener Diode

Pin 1 is the ON/OFF control pin, I expect 5v or higher, if it does not have any voltage at this pin, there will be no output at pin 4. Do verify that your meter has accurate reading.

[mr.sky]

Re: Panasonic TC-42PX14 Zener Diode

Pin 1 is the ON/OFF control pin, I expect 5v or higher, if it does not have any voltage at this pin, there will be no output at pin 4. Do verify that your meter has accurate reading.

pins 1,3 and 5 had no voltage. Yes, I will check my meter. but it seems
stable when I measure the 5v standby.

[retiredcaps]

Re: Panasonic TC-42PX14 Zener Diode

Will take those voltage readings tomorrow, seems my Amprobe 38
meter, needs another battery.

The Amprobe 38XR is a quality multimeter, but the battery life is low at 75 hours with a carbon zinc battery and 150 hours with an alkaline.

[budm]

Re: Panasonic TC-42PX14 Zener Diode

But you do get Voltage at VCC pin 2, right.
I updated the PDF to rev2 showing the on/off control of the IC502.
Since the Control signal at pin 1 is 0V, it means that it detects AC FAIL some how.

[mr.sky]

Re: Panasonic TC-42PX14 Zener Diode

But you do get Voltage at VCC pin 2, right.
I updated the PDF to rev2 showing the on/off control of the IC502.
Since the Control signal at pin 1 is 0V, it means that it detects AC FAIL some how.

yes, pin 2 was 21v, after I fix my meter, will try again.

[mr.sky]

Re: Panasonic TC-42PX14 Zener Diode

budm, replaced battery on Amprobe Digital Meter, and get same
results. No voltages at pins 1,3,5, but it is strange pin 2 gets
around 18 to 19v. Got out my reliable Analog meter, and same
results. On the pins 1,3,5 needle did not even move, on pin 2
it read close to 18vdc.
You mentioned if pin1 is not working possible problem in AC
circuit.

[budm]

Re: Panasonic TC-42PX14 Zener Diode

You are getting the Input to the regulator OK, but the ON/OFF control pin 1 is not getting the ON control to turn it on, that can be due to detector circuit that monitor if circuit is getting AC to the TV. Please see the revision 2 of the PDF.

[mr.sky]

Re: Panasonic TC-42PX14 Zener Diode

You are getting the Input to the regulator OK, but the ON/OFF control pin 1 is not getting the ON control to turn it on, that can be due to detector circuit that monitor if circuit is getting AC to the TV. Please see the revision 2 of the PDF.

Should I just back track from pin 1 and check caps, diodes etc.
also Q505 does have the 5volts on 2 pins.

[budm]

Re: Panasonic TC-42PX14 Zener Diode

If you follow the AC fail H signal on the PDF, I have notes as to what you should have at the test points.
On the first page, the OPTO isolator IC 600 PIN 3 and Pin4 should have less than a volt at those pins.
You can short pin 3 and pin 4 of the IC600, then you should have the 17v OUTPUT at pin 4 of the IC502.
As you can see, when you have AC feeding the TV, AC DETECTOR IC200 will send the signal to turn on IC600 which it then sends the LO signal to IC603 pin 19 to tell IC603 that it detect main AC input, then IC603 pin 16 will send out a HI signal to turn on 15V regulator IC502 to turn on its output to send out the regulated output at pin4.

[mr.sky]

Re: Panasonic TC-42PX14 Zener Diode

If you follow the AC fail H signal on the PDF, I have notes as to what you should have at the test points.
On the first page, the OPTO isolator IC 600 PIN 3 and Pin4 should have less than a volt at those pins.
You can short pin 3 and pin 4 of the IC600, then you should have the 17v OUTPUT at pin 4 of the IC502.

O.K. will give it a try, have to pick up my Grand daughter in Turlock.
I see you are from the bay area, worked there for 25yrs, east bay
mainly. now disabled and retired. will give you results later.

[mr.sky]

Re: Panasonic TC-42PX14 Zener Diode

I checked the IC 600 Opti-Isolator. pin3 no voltage at
all, pin 4 a little less than a volt. I jumped them to see, if
I would get less than a volt on both pins, now no voltage.
So, I take it that IC 600 is defective.

[budm]

Re: Panasonic TC-42PX14 Zener Diode

Solder pin 3 and 4 of the Opto IC600 together, then plug the TV in, then you should see IC603 pin16 and PIN1 of IC502 goes HI.

[mr.sky]

Re: Panasonic TC-42PX14 Zener Diode

Solder pin 3 and 4 of the Opto IC600 together, then plug the TV in, then you should see IC603 pin16 and PIN1 of IC502 goes HI.

I soldered the pins 3 and 4, and IC502 dc voltage reading is 00.03v pin 1

[budm]

Re: Panasonic TC-42PX14 Zener Diode

OK, you can remove the jumper.
I look deeper in the diagram and find that the F15V command comes from the IC603 PIN 16, the control signal to turn on pin 16 is fed into IC603 PIN9 (this signal is called by many names, F_STBY_ON or TV SUB ON or AG_TV_SUB_ON), this signal comes from SYSTEM MPU IC1100 PIN28. So some how this MPU is not sending out the signal to turn on this F15V REGULATOR IC.
I do not have complete understanding on how this MPU works, it may be in the locked-out mode due the error detection some where, this is about as far as I can go for you,.
The bad part about this service manual is that they keep changing the name of the signals, hard to trace them out.

[mr.sky]

Re: Panasonic TC-42PX14 Zener Diode

OK, you can remove the jumper.
I look deeper in the diagram and find that the F15V command comes from the IC603 PIN 16, the control signal to turn on pin 16 is fed into IC603 PIN9 (this signal is called by many names, F_STBY_ON or TV SUB ON or AG_TV_SUB_ON), this signal comes from SYSTEM MPU IC1100 PIN28. So some how this MPU is not sending out the signal to turn on this F15V REGULATOR IC.
I do not have complete understanding on how this MPU works, it may be in the locked-out mode due the error detection some where, this is about as far as I can go for you,.
The bad part about this service manual is that they keep changing the name of the signals, hard to trace them out.

The power command from the power switch on the S board or the remote control receiver on the K board is
provided to the Main CPU on the A board (IC1100) thru connector A1. The CPU on the A board outputs the
“TV_SUB_ON” Command (3.2V) and the PANEL_STB_ON” command (3.2V).
The “TV_SUB_ON” command is provided to pin 6 of connector P7 of the power supply through pin 14 of
connector A6 of the A board to develop the F_STB+15V. At this time the relays on the power supply are
triggered and a “click” sound can be heard.
The F+15V from the P board is applied to several voltage regulator (IC5603, IC5401, and IC5607) on the A
board.
The voltage outputs from these ICs are called SUB5V, SUB9V, SUB3.3V, SUB1.8V, SUB1.3V, and BT30V.
They used by various circuits on the A board.
To avoid catastrophic failures, they are monitored by an SOS Detect circuit (IC5480) for over-voltage and
over-current conditions. This SOS Detect circuit is controlled by the TV_SUB_ON command from the Main
CPU (IC1100).
Any abnormalities of the SUB5V, SUB9V, or BT30V triggers the SOS circuit. The TV shuts down and the
power LED blinks 10 times.
The “PANEL_STB_ON” is used to turn on the 3.3V regulator (IC9004) on the A board. The output voltage is
applied to the “Panel” CPU on the A board (Formerly located in the D board).
The Panel CPU on the A board outputs the “PANEL_MAIN_ON” Command (3.2V) to pin 11 of connector
P25 on the P board.
The PANEL MAIN ON command turns on the power supply circuit that outputs the Vsus, Vda, 15V, and 5V

My A-board does not have IC9004, also I do not get the 3.2v on pin 11 of
connector P25 on PB.
I did find a 5pin voltage regulator on page 72 of A-Board
This could be the reason pb will not turn on, I have to find why 3.2 is not
reaching pin 11 on A25 connector and then feed it to P25.
Thanks for all your help, please let me know if something pops up in
your mind. I will now pay my attention to the A-board.

[budm]

Re: Panasonic TC-42PX14 Zener Diode

"“TV_SUB_ON” Command (3.2V) and the PANEL_STB_ON” command (3.2V).
The “TV_SUB_ON” command is provided to pin 6 of connector P7 of the power supply through pin 14 of
connector A6 of the A board to develop the F_STB+15V. At this time the relays on the power supply are
triggered and a “click” sound can be heard." and "This SOS Detect circuit is controlled by the TV_SUB_ON command from the Main
CPU (IC1100)."
So at this point the IC1100 is not putting out the TV_SUB_ON signal that I traced it back to IC1100 are due to? Who is controlling the TV_SUB_ON?

[mr.sky]

Re: Panasonic TC-42PX14 Zener Diode

"“TV_SUB_ON” Command (3.2V) and the PANEL_STB_ON” command (3.2V).
The “TV_SUB_ON” command is provided to pin 6 of connector P7 of the power supply through pin 14 of
connector A6 of the A board to develop the F_STB+15V. At this time the relays on the power supply are
triggered and a “click” sound can be heard." and "This SOS Detect circuit is controlled by the TV_SUB_ON command from the Main
CPU (IC1100)."
So at this point the IC1100 is not putting out the TV_SUB_ON signal that I traced it back to IC1100 are due to? Who is controlling the TV_SUB_ON?

budm, Yesterday I mentioned that my A-Board did not have IC9004
well, I did find it on Page 31, it is next to IC 1100. I followed the sub 9v,5v and 3.3v from Page 30, the sub 3.3 and 5v, come from IC 5607 and the
sub9 from IC 5401, from there they go to IC 1100
IC 9004 is a 32 pin. I am hoping one of the components that go to IC 1100
that are fed from IC 5607 or possible bad IC 5401.
I also note after IC 9004, from there it goes to IC 9003 a pin there goes to
Connector A25, that is Main Panel On. pin 11, which should have 3.2v. There
is no reading there. Of course from there it goes to P board to turn on the F15v

[mr.sky]

Re: Panasonic TC-42PX14 Zener Diode

Well, I am pretty sure my problem with the Blinking 10, at least in my
unit is Q5522. It is a transistor, not sure if it is NPN. Schematics or
part #B1ADCE000022 will identify what type of transistor it is. I did
a google search and could not find info, other that it is out of stock.
According to page #30 of Schematics it says TUNER SOS below the
words it says LED:10 TIMES, I followed the black line and it goes to
the Tuner of A board., it also goes to TV SUB ON via pin 14 Connector
A6, that of course goes to Power Board.

[budm]

Re: Panasonic TC-42PX14 Zener Diode

What page this Q5522 is on?
OK, I found it, it is an PNP transistor.
For that transistor to turn on, the bottom end of the resistor R5536 will have to go low to let 5VSTBY current to flow out of the Collector pin. When that transistor is turn on, it will send the signal indicating that there is power supply failure, it should be normally OFF.
D5521 and D5522 are setup as an OR gate, if the Cathode side goes low due to missing power to make the Diode forward bias, then Q5522 will conduct which indicate one of the 4 power supplies had failed. Since you do not have F15, that means the top Diode of D5521 will be forward bias, so it turns on Q5522, so you will get error light.
That is why we need to get the F15V to work.