Periodically problems in PSU type: Antec SP350 P

[Hurup]

Hello I have some periodically problems in my old PSU type: Antec SP350 P

I have made following measuring on the PSU when it's operating the computer.

All the results of voltage measuring are placed in the centre of the specification except the – 12 volt.

The -12volt are measured to -11,45volt some times little higher -11,55volt.

In the Specification for SP350 P following detail is shown: -12volt +-5% (-11,40 – 12,60)

I have observed that the Power good signal pin 8 some time changes to 0 and the CPU stop running. The -12 voltage is then measured to -11,40volt, so safety circuit in the PSU is well working.

My question is:

How do I adjust the voltage, it‘s fixed, so I think it is one or two defective capacitors, but witch one?

Can someone give a solution?


Mvh

Hurup

[mockingbird]

Re: Periodically problems in PSU type: Antec SP350 P

This PSU will need a full capacitor replacement.

In order to do so, you'll need to remove the PSU cover and then unscrew the PSB from the chassis. Then you can desolder the live and neutral wires going from the socket to the PCB as well as the two thin switch wires. Once you have the PCB free from the chassis, you can start to desolder -all- the capacitors and document their properties in the following format:

Voltage, Capacity, Width * Height (In mm), Brand, Series

So, for example:
16V 3300uF, 10x30, Fuhjyyu "TN"

[Hurup]

Re: Periodically problems in PSU type: Antec SP350 P

Thank you for response.

I don’t understand why you will change all the electrolytic capacitors!

As I wrote, the supply voltage: -5v, +5v, +3,3v, +12v, st.by 5v are measured to be very fine. The values are in the centre of the specifications, you have +-5% safety. All measuring on running computer!

It’s only the -12v that gives the periodically problem and shut down the PSU (pin 8 goes low) when the -12v degrease to -11,40v equal to (-12v -5% = -11,40v).
Specification: -12v +- 5%, 0,3a

When the computer is operating I can measure -12v voltage switching around -11,50v.

Now I have removed the electrolytic capacitor mounted in the output for -12v.
The type is: manufacture is Teapo 330 micro 16v.

I have suspect to this electrolytic capacitor; maybe the problem is the ESR that is too high?

As I can conclude all the switching and safety system running well! I can’t see any physically change of the electrolytic capacitor as you normally can in Samsung, LG television and screens.

Specifically about PSU for computer I am beginner, but have 40 years experience in electronics.

Regards

Hurup

[cheapie]

Re: Periodically problems in PSU type: Antec SP350 P

Thank you for response.

I don’t understand why you will change all the electrolytic capacitors!

Because this particular power supply is known to kill all of them eventually. If you just replace the one, you'll be back in there eventually to replace more.

Besides, just because the voltage is in spec doesn't mean that the ripple/noise is.

[goodpsusearch]

Re: Periodically problems in PSU type: Antec SP350 P

Those Antec power supplies combine a terrible capacitor selection and a fan controller circuit that keeps the psu insanely hot.

I always do a full recap AND a fan mod to keep the new caps cooler.

[c_hegge]

Re: Periodically problems in PSU type: Antec SP350 P

Yup. Replace every single cap, including all of the small <100uF caps. My usual way to deal with the fan controller is to add a 2.4K or 2.5K resistor in parallel with the fan control thermistor. I usually replace the front fan on them too, since I often find them with stuck front fans.

[mockingbird]

Re: Periodically problems in PSU type: Antec SP350 P

No need to replace the fans when they can be refurbished... Just peel off the sticker, remove the rubber cover, take out the spring clip and lift it from the sleeve. Then clean the shaft and sleeve with some acetone and a q-tip... Mix some PTFE bearing grease with your favorite thinning oil (This step can be omitted, but the PTFE grease alone will slow down the fan slightly) and apply liberally with a toothpick.

Regarding your fan MOD, I didn't end up doing it because my system is only getting some 200W of power draw if even that... And the fan does kick in by itself eventually without the mod. I'm afraid that with the mod, the fan will stay on even after the system turns off. Is this the case?

[c_hegge]

Re: Periodically problems in PSU type: Antec SP350 P

No need to replace the fans when they can be refurbished... Just peel off the sticker, remove the rubber cover, take out the spring clip and lift it from the sleeve. Then clean the shaft and sleeve with some acetone and a q-tip... Mix some PTFE bearing grease with your favorite thinning oil (This step can be omitted, but the PTFE grease alone will slow down the fan slightly) and apply liberally with a toothpick.

You can do that with the rear one, but the 10mm front fan has no rubber plug, so any lubricant you put in just leaks out and the fan quits again.

Regarding your fan MOD, I didn't end up doing it because my system is only getting some 200W of power draw if even that... And the fan does kick in by itself eventually without the mod. I'm afraid that with the mod, the fan will stay on even after the system turns off. Is this the case?

For the fan to stay running after the PC is off, it has to have special circuitry to power the fan from the 5vsb, which the SP series lack altogether. Adding the resistor in parallel with the thermistor just means that both fans stay running whenever the PSU is on, and that they ramp up sooner. 200W power draw will get an SP-350 quite toasty.

[mockingbird]

Re: Periodically problems in PSU type: Antec SP350 P

Ok thanks. No, I've got the SP-450... Then PTFE bearing grease is good for those fans without the rubber plug. The stuff is pretty viscous and will not leak out. All you need to do is seal the hole with good electrical tape so that no dust gets into the sleeve.

[Hurup]

Re: Periodically problems in PSU type: Antec SP350 P

Thank you to all for the feedbacks.

I am very surprised at the quick and useful response.

With regard to change all the capacitors, I acknowledge that it may be necessary.

For ripple voltage level, I have had an oscilloscope in order to control and it showed very small and acceptable levels of ripple.

I have changed the 330mikro capacitor, but still have the problem on the -12v supply.
Subsequently, I found that the -12v supply is not used in the computer as there is no com port installed.

My periodic problem might be bugs, cold soldering on the safety circuit for good voltage pin 8.
The voltage at pin 8 switches suddenly short from 4.3 V to 0 and back then the computer resets and reboots.
This error can be triggered by mechanically affect the box with the power supply but I don’t checked it yet.

I will modify the fan control as described, thank you!

Regards

Hurup

[momaka]

Re: Periodically problems in PSU type: Antec SP350 P

You can do that with the rear one, but the 10mm front fan has no rubber plug, so any lubricant you put in just leaks out and the fan quits again.

I have serviced plenty of truly "non-serviceable" fans like that before (and by that, I mean not just fans that didn't have a rubber plug, but also fans where I had to actually drill a hole through their back to get to the c-clip that holds the rotor shaft). Never had problems with them, though - at least with the good ones. The key is to clean the sleeve bearing very well. If you use a small screw driver or something that is slightly abrasive and small enough to fit in the bearing, you then make scratches and "channels" parallel to the shaft direction. Then clean with paper towel and lubricate. Those scratches will make the bearing retain the oil a lot longer. If the fan was very "stuck" when you found it, the bearing might be quite worn. In such cases, I also rotate the fan 90 degrees when I install it back in the PSU. If the PSU is to go back in the same orientation that it was before (which, for most cases where the PSU is on to is, PCB in PSU is upside down).

200W power draw will get an SP-350 quite toasty.

Yes. Any PSU with "average" efficiency will get toasty. Think about it. If the PSU is 80% efficient, that means you'll be dissipating 20W for every 100W of power draw from the wall. So for 200W from the wall, you have about 40W (mostly) dissipated by the heatsinks. With a very slow fan, they could reach some hot temperatures.