Philips Power Supply - No output voltages!

[Perce2]

Having an issue trying to get my home-theater to power up, pretty sure it's a power supply related problem.

Here's where I'm at, stuck with what to check next...

Philips HTB5580/98 Home Theater, 18months old.
Problem - Not power up!
Symptoms - Problem started with unit not powering up sometimes, or only staying on for around 2mins. Then turned off with no standby LED.
Got worse, now not power up and no standby LED.
Remove power, replace and standby LED only stays on for around 1 - 2 seconds.

Local AC voltage should be 220v - we only ever get around 200v !
Voltage at main filter capacitors - 280v DC

TNY179PN - replaced with TNY279PN
TOP261EN - replaced
Optocouplers - replaced
Main Filter Capacitors - removed, tested with ESR meter + capacitance meter - tested OK
Secondary Capcitors replaced:
CE516
CE505
CE506
CE507
ZD503 - replaced

Removed both transformers and tested with DMM + Analog, both primary and secondary give very low resistance values.
Don't have an insulation resistance tester.

Visual inspection and tested all components best I can using Digital MM, Analog MM, ESR meter, Capacitance meter.
Don't see any more than 0.6v at any of the output voltages (voltage varies slightly between pins). Should be 34v, 12v, 5v.
Tested voltages with power supply connected to mainboard + amplifier + DVD and standalone and by removing connectors from the other boards one at a time.

Have checked resistance between voltage out pins and ground using analog meter on 1x, get very low readings but can't find aything shorted on each rail.
Any suggestion on what to check next ?



Circuit Diagram

[Quaddro]

Re: Philips Power Supply - No output voltages!

The main priority actually is the small capacitor..like ce508 and ce511.
Because it leak, dry or damage faster and without any deformation than the bigger caps.
Try to change all small capacitor too.

and, what about secondary rectifier, diodes and zener..?
Have you checked that too..?

zener is not uncommon fail under load, but if we measure with multimeter, it's seem good.

[budm]

Re: Philips Power Supply - No output voltages!

Yep, check or replace those two start up/running caps for that TNY IC.
Also check and provide the DC Voltage of all the pins of that TNY IC.
You can test the board by itself since that TNY IC is for the always on Standby power supply.

[Perce2]

Re: Philips Power Supply - No output voltages!

The main priority actually is the small capacitor..like ce508 and ce511.
Because it leak, dry or damage faster and without any deformation than the bigger caps.
Try to change all small capacitor too.

and, what about secondary rectifier, diodes and zener..?
Have you checked that too..?

zener is not uncommon fail under load, but if we measure with multimeter, it's seem good.

Have removed the cap's, tested with both ESR + Capacitance meter, tested fine. As I don't have any spare parts, I only originally ordered and replaced the parts that were out of acceptable tolerances except for the 2 IC's which I just replaced even though they tested ok.

I have now ordered in those small cap's to swap out.
Large diodes have also tested ok. The zener's I have already but didn't think it necessary to change as they also tested ok. As you suggest I'll also swap them out too. Any one in particular to try first ?

Thanks for your suggestions.

[Perce2]

Re: Philips Power Supply - No output voltages!

Yep, check or replace those two start up/running caps for that TNY IC.
Also check and provide the DC Voltage of all the pins of that TNY IC.
You can test the board by itself since that TNY IC is for the always on Standby power supply.

Hi budm, have already replied to your suggestions in my other post over in the Audio. Thanks again for your time.

[Perce2]

Re: Philips Power Supply - No output voltages!

and, what about secondary rectifier, diodes and zener..?
Have you checked that too..?

zener is not uncommon fail under load, but if we measure with multimeter, it's seem good.

Swapped out D509, D510 + ZD505 and now we have power !
All power rails are back up at the correct voltages.

The only problem I now see is the small 12v extraction fan fed from the amplifier board is not working. Checked voltage at the fan feed plug only showing something like 0.0035v.

Could this be fed from some thermo device that only runs at a certain temperature or should it run all the time the amp is on ?

Many thanks for the advice so far guy's...

[budm]

Re: Philips Power Supply - No output voltages!

Swapped out D509, D510 + ZD505 and now we have power !
All power rails are back up at the correct voltages.

The only problem I now see is the small 12v extraction fan fed from the amplifier board is not working. Checked voltage at the fan feed plug only showing something like 0.0035v.

Could this be fed from some thermo device that only runs at a certain temperature or should it run all the time the amp is on ?

Many thanks for the advice so far guy's...

Glad to gear the power supply comes alive again, the DIODE network that you replaced is part of the BP/M (pin 2 of the TNY), that is why I request the DC Voltage reading of all the pins of the TNY.

[Perce2]

Re: Philips Power Supply - No output voltages!

Many thanks budm...
Any idea regarding the 12v fan ?
Can confirm the fan actually works fine, hooked it up to a 12v supply to confirm.

There is no 12+v at the small connector plug on the board (only 3.5mV).
Rest of the amp is working fine.

Have a circuit diagram if it helps -

Thanks for any comments.

Image showing the amp with fan

[R_J]

Re: Philips Power Supply - No output voltages!

The fan is controlled by the MCU_CON_FAN line, check the voltage on that line, I suspect the fan only comes on when the amp is hot (run the amp for a while and see if the fan cuts in)

[Quaddro]

Re: Philips Power Supply - No output voltages!

now we have power !

Congratulations

[Perce2]

Re: Philips Power Supply - No output voltages!

The fan is controlled by the MCU_CON_FAN line, check the voltage on that line, I suspect the fan only comes on when the amp is hot (run the amp for a while and see if the fan cuts in)

Checked the voltage as suggested, only getting around 3.5mV.
If the MCU is controlling the fan would there be a voltage there all the time ?
Surely a voltage would only be present when the fan should be on, if controlled by temp or something ?

Left it switched on for quite some time, fan didn't start up.
Is there a way to check the MCU ?

Attached diagram showing what I get:



Amp PCB:

[budm]

Re: Philips Power Supply - No output voltages!

It does look like the MCU will turn the fan on when needed I.E. temperature too high.