Philips 20PF4121/58 power inverter board problem

[JohnNovak]

Re: Philips 20PF4121/58 power inverter board problem

Main filter cap voltage = 321V
MOSFET drain voltage variable from 321V to 329V.
IC pin8 voltage at R122 variable from 309V to 314V.

[R_J]

Re: Philips 20PF4121/58 power inverter board problem

Yes you can disconnect the board, and work on it off the chassis. you may not get the 12 volts but you should get a good 3.3 volts
When checking voltages on the primary (or HOT) side, be carefull and always use the (-) of the main filter cap as ground.

Also check the voltage on the fet drain, it should be close to 350 volts

[JohnNovak]

Re: Philips 20PF4121/58 power inverter board problem

Is it safe to disconnect the board from chassis and connect to 230V?
I never do this.
I do not understand where to measure?
The voltage between hot gnd and pin8 i think.

[R_J]

Re: Philips 20PF4121/58 power inverter board problem

Is it posible to provide the voltages that you get on U101? maybe there is a clue somewhere.
As a caution and to prevent sorting pins, measure the voltage on a component connected to the pin IE: for pin 8 measure on R122

[JohnNovak]

Re: Philips 20PF4121/58 power inverter board problem

Check the diodes in the secondary and see if any are shorted. If you disconnect the plug to the main board does the 3.3 volts stay constant?
There is a small elec. cap. in the primary, you could try replacing it. (near u100 opto)

Sorry i overlook this advice.

I disconnect also main board (small signal board).
There is option to manual power up the board to connect pin ST.BY to +3.3V
and load outputs with 12 ohm resistors.
This info is from service manual.

There is no power up also.

I also check main board with external power +3.3V and 12V.
I got green led normally, looks the main board is working.

[JohnNovak]

Re: Philips 20PF4121/58 power inverter board problem

Capacitor smd C131 is not present on the board.
The voltage goes from D104 to CE108.
Voltage on CE108 is the same as voltage on PIN1 on IC TEA1532A,
is variable goes up and down, from 9.33V to 10.40V.

Original FET is not shorted, nothing is shorted here what i checked for now.

[R_J]

Re: Philips 20PF4121/58 power inverter board problem

Sorry, I uploaded the wrong file, I was looking at the first post for the number. For some reason that VCC voltage is not coming up above 10 volts to keep the circuit running, The small winding on the primary side should go to a resistor (R133 1Ω) then to a diode (d104?) It should charge C131 to about 20 volts to keep the circuit working.

Was the original FET shorted or does it still check ok?

[JohnNovak]

Re: Philips 20PF4121/58 power inverter board problem

I replace CE108, 47uF/50V the same situation.
Main IC is TEA1532A and is not TEA152x series.

[R_J]

Re: Philips 20PF4121/58 power inverter board problem

I would try replacing that small elecrolytic cap. in the primary, CE10?
Here is the pdf of the ic.

[JohnNovak]

Re: Philips 20PF4121/58 power inverter board problem

The voltage on PIN1 on IC TEA1532A is variable goes up and down, from 9.33V to 10.40V.

[JohnNovak]

Re: Philips 20PF4121/58 power inverter board problem

Main IC = EA1532A

Voltage on main filter capacitor is stable.

Will measure voltage on pin 1 on primary IC today.

[nomoresonys]

Re: Philips 20PF4121/58 power inverter board problem

"Voltage on main filter capacitor is 326V DC" Do you have this steady voltage while the other voltages are low and or flucuating?

[R_J]

Re: Philips 20PF4121/58 power inverter board problem

If the primary was not operating at all you should not get anything on the 12 volt line either. It is likely it is trying to start and shutting down, just pulsing enough to make a small voltage on the 12 volt line.
Is the main ic a TEA1523A
What is the vcc voltage on pin 1 of the primary ic? You need to have negative probe of meter on hot ground to measure it
The start voltage is min 9 volts, if the voltage is below 8 volts the ic will stop working

[JohnNovak]

Re: Philips 20PF4121/58 power inverter board problem

I check from +3.3V to transformer secondary output,

+3.3V>>L108>>CE101>>C127>>L101>>CE107>>D101

nothing found.

I suspect that primary side have a problem and is shuting down, wish to start but something is wrong here.

[R_J]

Re: Philips 20PF4121/58 power inverter board problem

If you are getting 2.8-3.4 on the 12v, you should be getting something on the 3.3 volts, check components between the 3.3v at the plug, back to the transformer

[JohnNovak]

Re: Philips 20PF4121/58 power inverter board problem

There is no 3.3V on connector, voltage is 0.88 to 0.94V only.
At +10V output is variable voltage 2.8V to 3.4V and yes it stay some time
the same when i disconnect the plug.
+12V output have 0.28V only.

I check diodes are OK there is no shorts at secondary side.

[R_J]

Re: Philips 20PF4121/58 power inverter board problem

Check the diodes in the secondary and see if any are shorted. If you disconnect the plug to the main board does the 3.3 volts stay constant?
There is a small elec. cap. in the primary, you could try replacing it. (near u100 opto)

[JohnNovak]

Re: Philips 20PF4121/58 power inverter board problem

Have no schematic how this parts are connected.
Very hard to see from board.

Voltage on main filter capacitor is 326V DC.
Main fuse was no damaged during electrical shock.

Output DC voltages are:

+10V output = not stable = 2.8V to 3.4V goes up and down
+3.3 output = 0.88V to 0.94V
+12V output = 0.28V

[R_J]

Re: Philips 20PF4121/58 power inverter board problem

Was the main a/c fuse bad (open) or was it still good? did you have any voltage on the secondary plug? ie standby voltage,likely the 3.3 volts
Also what is the voltage across the main filter cap (100µf/450v)

[bobbyskillz]

Re: Philips 20PF4121/58 power inverter board problem

I think the white SMD GAS102 and GAS103 are gas discharge tubes. Can you check continuity across them? Maybe they failed short?