Newbie asking for help. Thermaltake SL-B220SFX PSU dead.

[DSpawnZ]

Hi. Greetings from Argentina.
I'm having trouble with this PSU that was given to me. Previous owner discarded it without repair attempt.
I'm very new to PSU repair but have knowledge in electronics.
The PSU only has +5vsb and does not turn on when PS_ON is grounded.
I've checked every major capacitor with a capmeter, but I have no means to measure ESR. All caps measured good. Their brand is ANODIA.
PSU has 3 NPN Power Transistors that are good and 3 diodes at the output that are good.
All other diodes in the board measured good. All resistors measured good too.
I'm starting to think that maybe the PWM chip is dead, but as I have no experience with PSUs I'm in doubt.
PWM chip is "2012 GND202" and googling I've found this PSU is made by Solytech.
I'm lost!!. Any help would be greately appreciated.

Sorry for my english.

[kc8adu]

Re: Newbie asking for help. Thermaltake SL-B220SFX PSU dead.

no fan twitch?
start looking for shorted rectifiers.you say the 3 big ones are ok but sometimes a smaller one like -12 shorts.and it can be hidden.
at least we know its age.the chip of the year.
and this has input components.most cheap n nasty units have jumpers and empty spots.
anodia are crap.if you get it running replace them.

[everell]

Re: Newbie asking for help. Thermaltake SL-B220SFX PSU dead.

5vsb working is a good sign. Here is what I would do.

Fuse is OK or you would not have 5vsb. check the 115V/230V switch on the back of the power supply. If you are using 115VAC and the switch is in the 230V position, that could cause your problem. Measure the DC voltage across each of the two main input capacitors. Should be 160 volts across each one.

Next, if you have an oscilloscope, look at the output signals on the 2012 pwm chip. If they are present when you short PS_ON, the pwm chip is probably OK. At that point I would suspect the two 945 driver transistors. Attached is a schematic of the 2012 chip. This power supply is made by L&C/Solytech/Allied using the "chip of the year" series of pwm chips. I have seen several Allied power supplies using the Anodia brand capacitors.

[DSpawnZ]

Re: Newbie asking for help. Thermaltake SL-B220SFX PSU dead.

no fan twitch?
start looking for shorted rectifiers.you say the 3 big ones are ok but sometimes a smaller one like -12 shorts.and it can be hidden.
at least we know its age.the chip of the year.
and this has input components.most cheap n nasty units have jumpers and empty spots.
anodia are crap.if you get it running replace them.

No. No fan twitch. Not a single spike of output. Always flat.
I have measured every single diode onboard. All good.

5vsb working is a good sign. Here is what I would do.

Fuse is OK or you would not have 5vsb. check the 115V/230V switch on the back of the power supply. If you are using 115VAC and the switch is in the 230V position, that could cause your problem. Measure the DC voltage across each of the two main input capacitors. Should be 160 volts across each one.

Next, if you have an oscilloscope, look at the output signals on the 2012 pwm chip. If they are present when you short PS_ON, the pwm chip is probably OK. At that point I would suspect the two 945 driver transistors. Attached is a schematic of the 2012 chip. This power supply is made by L&C/Solytech/Allied using the "chip of the year" series of pwm chips. I have seen several Allied power supplies using the Anodia brand capacitors.

I have an oscilloscope. Will check with datasheet and report back.
What are the possibilities for the PWM chip to die?. Is it a common culript?
Other component I'd left unchecked is the optocoupler.

Cheers

[DSpawnZ]

Re: Newbie asking for help. Thermaltake SL-B220SFX PSU dead.

These are the measures from 2012 chip:

Pin 1: VCC : 1.551v (is this good?)
Pin 2: PS_ON 0.2v (shorted to gnd with a wire)
Pin 3: V3.3: 0.3v
Pin 4: V5 : 0.2v
Pin 5: PP: 0.18v
Pin 6: PG_IN: 0.1v
Pin 7: O1: 1.517v DC (checked with the scope)
Pin 8: O2: 1.516v DC (checked with the scope)
Pin 9: PG: 0.1v
Pin 10: FB: 0.6v
Pin 11: VREF: 0.2v
Pin 12: GND
Pin 13: COMP: 0.205v
Pin 14: NEG: 0.107v
Pin 15: SS: 0v
Pin 16: RI: 0.38v

Question: Pin 1 VCC shoudn't be 1.5v?

Cheers

[stj]

Re: Newbie asking for help. Thermaltake SL-B220SFX PSU dead.

no.
probably 5v
check small electrolytic capacitors.

[DSpawnZ]

Re: Newbie asking for help. Thermaltake SL-B220SFX PSU dead.

no.
probably 5v
check small electrolytic capacitors.

Well. After checking Pin 1 traces, I've discovered it takes supply from 5vsb thru a 10 ohm resistor and a 10pf cap in parallel.
This cap was shot. After removing and replacing the bad guy, VCC raised to 4.8 volts and now the PSU is alive and kicking!.
Now I will consider replacing all capacitors, just in case.
Thank you guys for providing me guidance and the datasheet.
Will try to help others in the laptop section, as reparing them is my daily work.

Regards.

[Behemot]

Re: Newbie asking for help. Thermaltake SL-B220SFX PSU dead.

It is 220watt right? What caps are there? Look pretty small, I guess about 1000 uF.

[everell]

Re: Newbie asking for help. Thermaltake SL-B220SFX PSU dead.

Congrats on a great repair. Pin 1 Vcc goes thru a steering diode to 5vsb. It also goes thru a steering diode to the 12 volt rail. When power supply is plugged into wall, the 5vsb provides power to start the power supply working. Once it is working, the other steering diode brings the voltage up to 12 volts. This pin then acts as the overvoltage/undervoltage supervisor.

[DSpawnZ]

Re: Newbie asking for help. Thermaltake SL-B220SFX PSU dead.

It is 220watt right? What caps are there? Look pretty small, I guess about 1000 uF.

Yes it's 220W, but I doubt it will reach that power. Right now it's powering a new AM1 motherboard with an Athlon 5350 (25WTDP), and a single hard disk, and it gets pretty warm. The fan starts quietly but after a few minutes it starts to be noticeable.
Caps are: 2 x 330uF x 200V

Congrats on a great repair. Pin 1 Vcc goes thru a steering diode to 5vsb. It also goes thru a steering diode to the 12 volt rail. When power supply is plugged into wall, the 5vsb provides power to start the power supply working. Once it is working, the other steering diode brings the voltage up to 12 volts. This pin then acts as the overvoltage/undervoltage supervisor.

Good to learn how it works. A single tiny capacitor has taken away 4 hours of my life (on a weekend!). Ha ha.

Thanks again for your great support.

[TELVM]

Re: Newbie asking for help. Thermaltake SL-B220SFX PSU dead.

... Right now it's powering a new AM1 motherboard with an Athlon 5350 (25WTDP), and a single hard disk ...

A 220W PSU is plenty overkill for that thrifty combination, to reach even 50W AC draw from the wall you'll have to OC and overvolt the 5350.

[DSpawnZ]

Re: Newbie asking for help. Thermaltake SL-B220SFX PSU dead.

A 220W PSU is plenty overkill for that thrifty combination, to reach even 50W AC draw from the wall you'll have to OC and overvolt the 5350.

Yes that was what I thought. I've measured the wall power and it's 53watts.
But the psu gets warm. Maybe the fan is spinning too slow. It's connected to a speed controller that senses the secondary heatsink temperature.
I will try to connect the fan directly to 12 volts.

Regards

[Behemot]

Re: Newbie asking for help. Thermaltake SL-B220SFX PSU dead.

Is it spinning freely? Maybe the bearing is seizing.

[DSpawnZ]

Re: Newbie asking for help. Thermaltake SL-B220SFX PSU dead.

Is it spinning freely? Maybe the bearing is seizing.

Yes. It spins freely. Now I have connected it to 12v bypassing the speed controller. I will check if temperatures have decreased.

[Behemot]

Re: Newbie asking for help. Thermaltake SL-B220SFX PSU dead.

I'd guess it is very noisy now…

[DSpawnZ]

Re: Newbie asking for help. Thermaltake SL-B220SFX PSU dead.

I'd guess it is very noisy now…

I can hear it now, but it's not that noisy. It's a dual bearing fan.