Faulty Philips PSU (715g5246-p01-000-002s )

[tom66]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

I've uploaded it under OEM.
I think I'll put future generic schematics in this directory.

http://www.tgohome.com/ServiceManual...&Search=Submit

I have a feeling that the manufacturer of these parts is BriView, from a little research, a relatively unknown company in China. Maybe I can get more of the 715G schematics from that server.

[budm]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

If you solder another 3K3 resistor in parallel with R9335, you should see the output voltage rise up if the opto is controlling.

[tom66]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

If the opto was leaky, the AZ432 should compensate, by pulling more current through, so I don't think changing the resistor will help -- AZ432 has been verified already. For the opto to fail, it would have to be really, really leaky.

[Mr_K]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

The SCH shows Q9301, R9339, R9341, R9340 as NC (NOT CONNECTED/NOT USED).
Check ZD9303, OPTO IC9303, REF DIODE IC9304 as Tom suggested.
The more PIN4 (FB) switng toward ground (less voltage), the less output voltage you will get. Check voltage between pin2 and 3 of ref diode IC9304.
When the output voltage tries to go up, the Opto will turn on more to keep the FB pin low.

ZD9303 is fine
Opto needs to be tested tomorrow (need a second multi)

V between Pin 2 and 3 of IC9304 is 1.76V

Will try the second resistor now

[Mr_K]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

If you solder another 3K3 resistor in parallel with R9335, you should see the output voltage rise up if the opto is controlling.

Still 2.94V on standby......

[tom66]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

Correction, second multimeter to measure current on current range (through opto transistor.)
Basically any generic optocoupler will work so it may be quicker to find one on an old power supply board and swap it.

[Mr_K]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

EDIT....my bad.....

[tom66]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

?

[budm]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

The harder the LED is turn on (the photo transistor will turn on more cause the FB pin to go lower), it will cause output to drop, it is negative feedback from what I see in the SCH, so if you reduce the current flowing through the LED, the the transistor will turn on less due to lower current transfer function. We are basically try to change the voltage level at the FB pin of the SMPS IC.

[Mr_K]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

New opto..... Same Problem

[tom66]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

This could prove very difficult to trace down then.

[budm]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

What do you read at the FB pin and the ground pin?

[budm]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

See explanation on page 9 on FB pin, the FB pin is sunk by the Opto, if the FB is < 0.95V it will stop the Oscillator.

[Mr_K]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

0.8V with new opto still installed.

[budm]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

That is not right at all, something is sinking that pin down, there is a zener diode connected to that pin per SCH. Lift one leg and take the resistance reading of the Zener and also resistance between FB pin and the ground pin.

[tom66]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

Perhaps the FB pin is leaky, or C9334, or ZD9303 are.

[budm]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

Never mind, I looked back at the long thread, it is 5.2V.
Disregard:
I am still not sure if the board STBY is 5v or 3.3V. He did not have the STBY until I have him changed the STBY IC.

[Mr_K]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

ZD9303 is too high to
FB to gnd is ~16meg

[budm]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

OK, this is what you can do, hookup the meter to monitor the 5.2V output and also have a small 6V lamp connected to the 5.2V Output, keep the meter hookup at all time. Apply the power to the board, then short/un-short pin 1 and pin 2 of the Opto IC 9303, you should see the voltage rise up everytime you short out the pin, if it does, then the IC is working, if not, I would replace the Opto, the IC 9304 1.25V ref diode..

[Mr_K]

Re: Faulty Philips PSU (715g5246-p01-000-002s )

Ok, when i short Pin 1 and 2 of opto IC9303, the voltage rises up to 5.7V and immediatly falls to 1.4V. and rises again. This repeats as long as the pins are shorted.

Edit: Sorry! Forgot to put the zener bach in place. Will try again....

Edit2: Ok, with the Zener back in place and the extra 3K3 removed, voltage comes up to 4.5v and drops to 1.5->4.5->1.5-> etc