Panasonic TC-42PX14 Zener Diode

[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

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.

[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.

[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

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

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

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.

[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.

[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.

[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.

[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.

[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

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

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.

[mr.sky]

Re: Panasonic TC-42PX14 Zener Diode

Will take those voltage readings tomorrow, seems my Amprobe 38
meter, needs another battery. Readings flucuate.
budm, so standby should always be there, without powering up
unit, correct? The only voltage i get on P6 connector is the
5vstandby. That is with just the power cord plugged in.

[mr.sky]

Re: Panasonic TC-42PX14 Zener Diode

IC502 is the standby power supply (15V) which should be always running. The other power supply circuits is right below it is also always on, do you get any voltage there? There should be voltage at Q505, that section is for the standby 5V power supply.
Basically, transformer T200 is for standby 5V and standby 15V power supply, so you MUST have these voltages.

I will check it out, I also tried another new power supply board
that I received last week. And the same results.
Who knows could be bad too, good thing I got it for 30bucks.
I am looking at page 32, and on top of board, there is a 3
leg diode, looks like a regular size voltage regulator, but it is
a diode, D502. Going to have lunch and test voltages like you
mentioned above.

[budm]

Re: Panasonic TC-42PX14 Zener Diode

IC502 is the standby power supply (15V) which should be always running. The other power supply circuits is right below it is also always on, do you get any voltage there? There should be voltage at Q505, that section is for the standby 5V power supply.
Basically, transformer T200 is for standby 5V and standby 15V power supply, so you MUST have these voltages.

[mr.sky]

Re: Panasonic TC-42PX14 Zener Diode

OK, I figure out where the F15V is generated from, see PDF/JPG attached.
This F15V is called F15V_STBY which is the always on standby power supply.
So you need to check the voltage at the IC502 which generated the regulated F15V voltages for a lot of circuits as I redlined.

budm, Thanks for the diagrams. let me update you and others who
are following this thread.
On first diagram where IC502, I am not getting 15v at all.
Before I press the power button, reading is at 3.0v. Once
I power up unit it goes to 5.4v, same reading I get at the
A Board at IC 5401 and IC5608.
Also, Pins 7,8,9 same voltages at connector P6.
The unit is only come on for a few seconds, enough to take
a reading then shuts down within 5 seconds.
Note, I took the reading from pin 4 of IC502

[budm]

Re: Panasonic TC-42PX14 Zener Diode

OK, I figure out where the F15V is generated from, see PDF/JPG attached.
This F15V is called F15V_STBY which is the always on standby power supply.
So you need to check the voltage at the IC502 which generated the regulated F15V voltages for a lot of circuits as I redlined.

[mr.sky]

Re: Panasonic TC-42PX14 Zener Diode

Ok, the IC5401 is a 9V voltage regulator, so the Zener Diode may be 12V Zener.
So next thing for me is to find out what generates the F15V source.

budm, read Slide #28 the last paragraph. I think this is why
I am not getting F-15v from outpins from power supply board.
There is a 3.3v 6pin voltage regulator on the component side of
the A board, maybe this is the one that triggers the command to
to acitivate the The PANEL MAIN ON command turns on the power supply circuit that outputs the Vsus, Vda, 15V, and 5V.
Let me note my A-board does not have IC 9004