Cheap PSU: Piece of junk or semi-decent?

[kc8adu]

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

didnt remember you mentioning a 100v part.
hell a 50v would give plenty of margin.

[TELVM]

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

i wouldnt do that.if anything use a higher rated part ...

I'm confused now ... :

... i doubt you need anywhere near 100v though.
i like twice the output voltage.
vf is lower on lower voltage parts so less heat ...

https://www.badcaps.net/forum/showthread.php?t=3759

[kc8adu]

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

i wouldnt do that.if anything use a higher rated part.lower vf however is good!less drop=less heat.

(Most amazingly)

Next I'm going to swap the +12V rectifier diode, let's see if lowering the Vrrm brings fireworks or not ...

.

[TELVM]

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

(Most amazingly) my switcher swap looks like a success.

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

No explosions and the PSU seems to work OK giving coherent voltages.


Next I'm going to swap the +12V rectifier diode, let's see if lowering the Vrrm brings fireworks or not ...

.

[TELVM]

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

Oh, roger , two Panny FC are underway.

[Th3_uN1Qu3]

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

"Electros" = short for "Electrolytics". So yes, those two is what he was talking about.

[TELVM]

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

While you're at it, replace those two small electros. They, along with some resistors and diodes, bias the two switchers ...

Beg your pardon: 'Electros' ? Do you mean those two small 10uF 50V caps?

[kaboom]

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

Thanks Momaka & c_hegge!

Harsh profanity was required but managed to unscrew the 13007s without desoldering the heatsink :

While you're at it, replace those two small electros. They, along with some resistors and diodes, bias the two switchers.

Miniature long- and needle-nose pliers are excellent for removing and replacing the screws and insulators for the power transistors.

Something like this, but with less bulky handles:
http://www.harborfreight.com/6-piece...set-94931.html

[Th3_uN1Qu3]

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

I always unsolder the whole heatsink, saves a lot of sweat.

[TELVM]

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

Thanks Momaka & c_hegge!

Harsh profanity was required but managed to unscrew the 13007s without desoldering the heatsink :

[c_hegge]

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

Would a couple Panasonic EE-TS 800uF 200V 105C 22x50mm Ripple=3.08 ESR=0.15 do the job OK?

Yes, those would be fine. The ESR isn't that critical for the primaries.

[momaka]

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

Most amazingly the 'TOOQ' hasn't exploded yet . But judging from the tropical heat that comes from PSU rear and the 311W from the wall that the Kill-a-Watt shows at full Preshott burner (311 x 0.8 = ~250W DC) it must be on the very edge of .

Yeah, it really is right on the edge - particularly the 12V rectifier. Efficiency of a cheap PSU is usually around 70%. With that in mind, 311 x 0.7 = 218 W. Most of that is from the 12V rail, so let's say 200 W. That means the 12V rectifier is providing almost 17 A.

So yeah, the 12V rectifier is probably the only thing you need to upgrade.

[TELVM]

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

Thanks a lot pals .

One last detail if you don't mind. To replace this crap :

Would a couple Panasonic EE-TS 800uF 200V 105C 22x50mm Ripple=3.08 ESR=0.15 do the job OK?

[Behemot]

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

I think that 60 V is usually suggested minimum for +12 V rail and STMiro part should not have any problem with that…

Just a notice, you should compare under same circuimstances. MBR has voltage drop specified as maximum at 10 A/25 °C. STPS has 0,405 V on the frontpage, but it is typical under different circuimstances. Under same conditions, it is 0,535 V. So be aware of that, quite often you can find parts are not that impressive as they seem on first view.

[goodpsusearch]

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

My guess is that it will be ok.

[TELVM]

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

Thanks c_hegge .

I'm also thinking on beefing up the +12V rectifier:


If '20150CTP' is something like the MBR20150CTP, it is a Schottky 20A, Vrrm=150, Vf=0.9 .

How about replacing it with a STPS40SM60CT? Double the amps and half the Vf. Would lowering the Vrrm from 150 to 60V make it go ?

[c_hegge]

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

Yup, it would do fine as well.

[TELVM]

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


As implausible as it sounds, both pieces of junk starring in this thread are still alive & kicking and stubbornly keep working like a charm .

The 'TOOQ' thing, complete with with its world famous ghetto-modded secondary PI coils , is now propelling a P4 Preshott overclocked to a non trivial 4.25GHz .

Most amazingly the 'TOOQ' hasn't exploded yet . But judging from the tropical heat that comes from PSU rear and the 311W from the wall that the Kill-a-Watt shows at full Preshott burner (311 x 0.8 = ~250W DC) it must be on the very edge of .

So I think the time has come to plunge into more serious PSU tinkering: The black art of switchers and rectifiers replacement .



The 'TOOQ' thing has this on the primary:

I think the 8A 13007s could perhaps be replaced with 12A 13009s.

The MJE13009G is out of catalog in Farnell. How about the Fairchild FJP13009H2TU, could it do the job?

.

[TELVM]

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

(Double post)

[Pentium4]

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

That thing looks GREAT! I can't help but not trust those Cheng caps though, and if they are really as much uF as they claim. Wouldn't want them limiting your awesome mods