VOGONS


First post, by doaks80

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Has anyone used, and can recommend, a PicoATX PSU for a retro build? Specifically:

asus p5a (SS7)
k6-3+ 400 (1.6v)
s3 virge DX AGP
voodoo1 PCI
1-2 ISA sound cards
CF/IDE adapter (no HDD)
ide cd-rom
around 5 case *fans*

What kind of wattage did mid-90s PSUs come with? Would 150W be enough? Output clean enough for a mobo?

Thanks.

EDIT: case case was mean to be case fans.

Last edited by doaks80 on 2019-01-21, 05:45. Edited 1 time in total.

k6-3+ 400 / s3 virge DX+voodoo1 / awe32(32mb)
via c3 866 / s3 savage4+voodoo2 sli / audigy1+awe64(8mb)
athlon xp 3200+ / voodoo5 5500 / diamond mx300
pentium4 3400 / geforce fx5950U / audigy2 ZS
core2duo E8500 / radeon HD5850 / x-fi titanium

Reply 2 of 19, by SW-SSG

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You don't have an HDD and are using a laptop-class CPU, so I'd bet even the 80w one would be enough.

A bigger problem might be the cables being too short and/or too few for whatever "around 5 case case" is.

EDIT: yeah, you might need to plug in some Molex splitters for those five fans.

Last edited by SW-SSG on 2019-01-21, 20:46. Edited 1 time in total.

Reply 3 of 19, by Super_Relay

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the biggest problem is that back in the day 200Watt power supplies had 100watts on their +5v rail and a pico psu is mostly weighted towards its 12v rail for modern CPUs and the 160w one only has about 40watts on its +5v rail.

just be mindful and if you start to have resets or shutdowns then you know what to look at first.

perhaps try to get parts that split the wattage between the 3.3, 5 and 12v lines to take the load off the weaker smaller voltage regulators.

Reply 4 of 19, by doaks80

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I will try something and let you know the result.

k6-3+ 400 / s3 virge DX+voodoo1 / awe32(32mb)
via c3 866 / s3 savage4+voodoo2 sli / audigy1+awe64(8mb)
athlon xp 3200+ / voodoo5 5500 / diamond mx300
pentium4 3400 / geforce fx5950U / audigy2 ZS
core2duo E8500 / radeon HD5850 / x-fi titanium

Reply 5 of 19, by SirNickity

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I would use those as a last resort. They're cool, but minimally capable. Their main trick is that most PCs will use the 12V rail primarily, which the Pico does not regulate. It's passed through a MOSFET switch (to enable PS_ON control), but otherwise power quality is up to the upstream DC power brick. So is short circuit or over-current protection. I think it monitors voltage to prevent powering up when the +12V line is wildly out of spec, but otherwise it has no control over ripple, regulation, etc.

The +3.3V and +5V rails are regulated, but anemic. The -12V rail is barely there. The -5V rail is not there at all. It's really not a great fit for AT or early ATX boards, and should be used with caution on modern ATX systems as well. It does work, but with compromises.

Reply 6 of 19, by Super_Relay

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SirNickity wrote:

Their main trick is that most PCs will use the 12V rail primarily, which the Pico does not regulate.

I dont think i could bring myself to use one of the unregulated ones on anything i cared about but the better ones definitely do regulate the 12 volt line. you can pick them because they use 19 volt power bricks and have reasonable heatsinks.

like this one
https://www.hdplex.com/hdplex-160w-dc-atx-pow … tage-input.html
(i have nothing to do with hdplex, just its an example of a better one)

Reply 7 of 19, by Revolter

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I've been using this cheap 120W Chinese PicoPSU knockoff with the signature PC for about a year now, and so far the system has been stable as a rock, even at the maximum overclock. Not sure if it's regulated 12V or not.

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Would still want to go for the real thing someday for peace of mind though, but the shipping cost to Russia is out of control 😀

Celeron 800, 512MB, GeForce2 MX, ES1938S/DB S2, Windows ME/DOS 6.22

Reply 8 of 19, by doaks80

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Revolter wrote:

I've been using this cheap 120W Chinese PicoPSU knockoff with the signature PC for about a year now, and so far the system has been stable as a rock, even at the maximum overclock. Not sure if it's regulated 12V or not.

dPiVJ_WP8_A.jpg

Would still want to go for the real thing someday for peace of mind though, but the shipping cost to Russia is out of control 😀

I noticed a number of them on eBay give ripple and max/min rating for the 12V rail...which seems only possible if regulated.

Can I ask what AC/DC you use to feed the PSU? What is the output amps? Also, what system are you powering with what components?

k6-3+ 400 / s3 virge DX+voodoo1 / awe32(32mb)
via c3 866 / s3 savage4+voodoo2 sli / audigy1+awe64(8mb)
athlon xp 3200+ / voodoo5 5500 / diamond mx300
pentium4 3400 / geforce fx5950U / audigy2 ZS
core2duo E8500 / radeon HD5850 / x-fi titanium

Reply 9 of 19, by SirNickity

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Super_Relay wrote:

like this one
https://www.hdplex.com/hdplex-160w-dc-atx-pow … tage-input.html
(i have nothing to do with hdplex, just its an example of a better one)

Yeah, that doesn't look too bad. Not a whole lot of capacitance, but if they're using a high enough switching speed that may be fine. My only concern is, all the components and the heat sink make it large and top-heavy for an ATX plug. If it fits, I would definitely take that one over the Pico ones that Mini Box sells. 😀 Good find.

Reply 10 of 19, by Revolter

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doaks80 wrote:

I noticed a number of them on eBay give ripple and max/min rating for the 12V rail...which seems only possible if regulated.

Can I ask what AC/DC you use to feed the PSU? What is the output amps? Also, what system are you powering with what components?

Thanks, good to know!

It's just a generic 12V x 10A power brick from the same seller. Nothing to say about it, really - other than that it emits a faint coil whine when the machine is not turned on (ATX pilot current). I heard you can make a pretty nice 200W AC/DC out of an XBOX' original PSU.

How much power does it draw from the wall is a mystery to me, as I don't have a meter. I bet it's something around 60 or 70 Watt.

The system is a Celeron 800 (sometimes @1066 Mhz), GF2MX 32MB, 1 stick of 512MB PC133 RAM, 1 PCI sound card, 1 USB Wi-Fi dongle, an SDCard-to-IDE adapter, 1 80mm fan at 7V and occasionally a USB DVD drive. I've also had it running with a PCI NIC + 2 256MB RAM sticks + IDE DVD drive - no problems there either.

Celeron 800, 512MB, GeForce2 MX, ES1938S/DB S2, Windows ME/DOS 6.22

Reply 11 of 19, by doaks80

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When I get the parts I will post pics of the project I am using it in.

k6-3+ 400 / s3 virge DX+voodoo1 / awe32(32mb)
via c3 866 / s3 savage4+voodoo2 sli / audigy1+awe64(8mb)
athlon xp 3200+ / voodoo5 5500 / diamond mx300
pentium4 3400 / geforce fx5950U / audigy2 ZS
core2duo E8500 / radeon HD5850 / x-fi titanium

Reply 12 of 19, by SirNickity

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Revolter wrote:

1 80mm fan at 7V

Aw man... the +5 and +12V trick? This thread is killing the engineer in me. 😅 That's another one of those things that's.... probably... going to be fine, but you really shouldn't. It's so much safer to get a low RPM fan with sophisticated bearing technology (maglev, hydro bearings, etc.), and/or use a 4-pin connector with a PWM controller, or (if the fan doesn't mind reduced voltage) use a regulator or even just some beefy power resistors to drop the voltage.

The problem with the 7V trick is that you're bridging two rails in a way that they aren't meant to be bridged. +5V is not meant to be a current sink. Usually it won't be, because the fan will return less current than the rest of your system is drawing, but you just can't guarantee that will always be the case.

Reply 13 of 19, by Revolter

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SirNickity, turns out I was wrong - it's 5V, from a standard issue Molex-to-3Pin fan header adapter that comes with many case fans. Don't know why I thought it was 7V, but thanks for the heads up - I won't be doing it like this if it's not safe 😀

Celeron 800, 512MB, GeForce2 MX, ES1938S/DB S2, Windows ME/DOS 6.22

Reply 15 of 19, by ajacocks

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I was using a PicoPSU 160XT, with a generic brick, to power my mini-386sx machine, for a few months. One day, however, it blew up with an impressive crack, and a visible arc. I suspect that this had to do with unregulated 12VDC power going _very_ high, from the iffy quality brick that I could find to supply 12VDC @ 10a.

As a better quality replacement, I have switched to a 200 watt TFX power supply. It's small enough to fit into older chassis, with a custom bracket, and seems to produce quality power. At $20 USD, it's a gimme.

- Alex

Reply 16 of 19, by Jonas-fr

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For testing purposes I use an ATX2AT (x86.fr) but I'm on the lookout for a simpler solution (less bell and whistles) for mobo I've tested and I want be put to use, so a PSU dedicated for AT machine (-5V, bigger 5V power rail, etc...) will be awesome.!It seems some guys from Poland have something cooking : https://translate.google.com/translate?sl=aut … %3D1597452596/4

I can't wait for a PicoPSU-AT !

Reply 17 of 19, by adalbert

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Hi, I posted that design in this topic: AT PSU design (question about output overvoltage protection)
here is a prototype for T3200SXC DIY AT DC-DC power supply (replacement for Toshiba T3200SXC and others)

unfortunately I didn't go beyond a prototype and I think this design should be modernised, for example throw out the relay and SCR and replace them with MOSFETs, etc (I'm not particulary good in designing more complex electronics) 😉 right now my solution for more powerful, but still reasonably small AT PSU is SFX form factor power supply with ATX - AT adapter...

And if you just want Pico PSU with -5V, you can piggyback a LM2662 module, this is what I did recently:

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it should be also possible to remove the ATX plug and solder AT connector wires directly. Pico AT is done 😉

Repair videos: https://youtu.be/T6mXM1tA7pA

Reply 19 of 19, by adalbert

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That's the reason for installing LM2662, it is a charge pump which converts positive +5V into -5V 😀 you solder +5V to +VIN on the module, and -VOUT goes to the -5V mainboard connector. -12V remains untouched in this scenario. LM2662 should provide up to 200mA, maybe less in real world conditions, but that should be enough.

Repair videos: https://youtu.be/T6mXM1tA7pA