Cheap PSU: Piece of junk or semi-decent?

[TELVM]

Re: Cheap PSU: Piece of junk or semi-decent?

Hmmm ... I've been beeping my way and the two PSUs are very dissimilar :


In the TOOQ four of the six 'secondary' legs of the main trafo seem to be put to ground, two go to +12V and apparently none goes to +5V.

Too baroque to tangle with, I think I'll live with the fake 35 for the time being .

[Behemot]

Re: Cheap PSU: Piece of junk or semi-decent?

Those are often not independent windings rather than single winding with several outputs. It is also usually thick wire, you won't be able to measure that unless you have precise meter (like ESR metr, inductance meter is better). Ordinary resistance meter is not precise enough and has higher transitional resistance on probes than the measured winding.

[momaka]

Re: Cheap PSU: Piece of junk or semi-decent?

Hmmm ... I've been beeping my way and the two PSUs are very dissimilar :

That won't do. Windings are all connected together so you can't use a multimeter.

What you need is to have both PSU boards in front of you and physically (i.e. with your eyes) trace the 3.3V, 5V, and 12V rails to their corresponding transformer pins. Start from the rectifiers for each rail and work your way backwards to the transformer.

For the transformer that doesn't have the separate ground tap, you should have 2 pins for 5V, 2 pins for 12V, and 2 pins for ground . On the one that does, it's possible that 3 of the pins are for 12V and 3 are for 5V... or 4 are for 5V and 2 for 12V. Or just 2 for 12V and 2 for 5V, and 2 unconnected.

[TELVM]

Re: Cheap PSU: Piece of junk or semi-decent?

By visual tracing it may be that the two center pins of the 'fake' go to +5V. Most definitely two pins go to +12V, and two to ground.

The two dubious pins in the 'true' seem to go to a resistor and a small lenticular ceramic cap, then seem to go to +5V. I can't tell for sure, the donor PCB is now almost empty of components and heavily mauled.

I don't know, sounds too baroque and risky a trasplant with my very limited tools and knowledge . Better I'll wait till I can scrounge some true 35 with a clearer pinout and no hanging wire.

Thanks a lot for your interest and your help , this is a fantastic forum for learning!

[Th3_uN1Qu3]

Re: Cheap PSU: Piece of junk or semi-decent?

Good luck with that, most halfbridge PSUs have that grounding wire on the transformer.

[TELVM]

Re: Cheap PSU: Piece of junk or semi-decent?

Well the TOOQ thing works fine after all the tinkering. Voltages are well inside ATX specs at any load. With the extra 80mm fan the air exiting from the PSU at full steam is now cooler, barely warm @ 21C ambient.



I've noticed that, even with the added fan drawing one or two extra watts, the Kill-a-Watt now shows ~15W less power draw from the wall at full steam (296 vs 311W previously), a ~5% efficiency improvement.

I suspect this comes from the new 40A +12V rectifier, beefier and with lower Vf.

[momaka]

Re: Cheap PSU: Piece of junk or semi-decent?

I suspect this comes from the new 40A +12V rectifier, beefier and with lower Vf.

Yeah, the lower Vf helped save a few watts.

[TELVM]

Re: Cheap PSU: Piece of junk or semi-decent?

The stranded 20A Schottky rectifier from the TOOQ has found a new home in the Allied PSU, which came with this anorexic 10A superfast on the +12V rail :

This time the insulating pad was not forgotten and it works, oh Deer!

[goodpsusearch]

Re: Cheap PSU: Piece of junk or semi-decent?

That's foresight .


If I read the colour codes correctly R1 is 330K (orange/orange/yellow/gold), R2 is 470K (yellow/violet/yellow/gold).

Maybe Deer ran out of 330K resistors half way through assembling it?

It is intentional after all...

I have an Allied 2006 psu with the same asymmetry in bleeding resistors!

R3: 462kohm and R4: 330kohm

And the best part is that it might have impact on the caps. The caps are Koshin 200V 470uF and their capacity is:
481uF (in parallel with 462kohm R3)
465uF (in parallel with 330kohm R4)

I am going to open a new thread for that psu soon.

[momaka]

Re: Cheap PSU: Piece of junk or semi-decent?

It is intentional after all...

I have an Allied 2006 psu with the same asymmetry in bleeding resistors!

Must be a design error then! Because I really don't see any reason for the dis-balance in the voltage over the caps. I bet the voltage across the two caps is slightly different too. Oh DEER!

[amede]

Re: Cheap PSU: Piece of junk or semi-decent?

I changed MOV and connected the green and black wire but still no answer in my PSU

[amede]

Re: Cheap PSU: Piece of junk or semi-decent?

Someone changed the psu from 230 to 110 mode while in our country is 240 and i sawone MOV blown I changed it but PSU doesn't work.Help me!

[stj]

Re: Cheap PSU: Piece of junk or semi-decent?

foto's

[Behemot]

Re: Cheap PSU: Piece of junk or semi-decent?

Fuse probably burned too. You can remove that voltage switcher completely while on 230 V.

[TELVM]

Re: Cheap PSU: Piece of junk or semi-decent?

My legendary 'TOOQ' frankenPSU concoction suddenly refuses to start. This PSU has not seen much use since it was frankensteined, just some hours a month powering a P4 retrocomp.

+5VSB is alive and well, but when I switch the PSU on the fans don't even blink, and the bulb trick just flashes once briefly.

On visual inspection everything looks OK, but after some meter testing it seems the +12V rectifier is blown:

Legs 1 Leg 2 (center): .001 continuous beep, Ω 1.7
Legs 3 Leg 2 (center): .001 continuous beep, Ω 1.7

This +12V rectifier is a STPS40M60CTN which replaced the original MBR20150CTP (max Vrrm = 60 vs 150):

Swapped the MBR20150CTP +12V rectifier for a STPS40M60CTN.

>Expand . . . >Expand . . . >Expand

With 40A it was way overkill for the application. I wonder if the repetitive reverse voltage has killed it.

[goodpsusearch]

Re: Cheap PSU: Piece of junk or semi-decent?

Interesting.

Maybe the Repetitive reverse voltage was too low for that platform.

The secondary heatsink is directly connected to the rectifier's output pin? I don't see any insulation.

[stj]

Re: Cheap PSU: Piece of junk or semi-decent?

schotky rectifiers usually have a snubber resistor&cap, was it there or added?

[TELVM]

Re: Cheap PSU: Piece of junk or semi-decent?

The STPS40M60CTN +12V rectifier is definitely blown, once unsoldered from the PSU one of its legs is shorted.

Maybe the Repetitive reverse voltage was too low for that platform.

That's my best guess.

The secondary heatsink is directly connected to the rectifier's output pin? I don't see any insulation.

Ahem , thas was an old mishap since solved, see here.

schotky rectifiers usually have a snubber resistor&cap, was it there or added?

The OEM MBR20150CTP was a Schottky, so I'd guess yes, but I can't really tell.

[goodpsusearch]

Re: Cheap PSU: Piece of junk or semi-decent?

Ahem , thas was an old mishap since solved, see here.

Ok.

Either the Repetitive reverse voltage was too low for that platform,

or else, something went wrong with the rectifier's insulation.

[TELVM]

Re: Cheap PSU: Piece of junk or semi-decent?

Heh heh I'm thinking about performing a little experiment ... what if I just cut off the shorted leg and put it back as a single-diode 20A rectifier ? Would it start?