You will need an adapter to wire the switch or an AT form factor switch that functions as an ATX switch.

Isn't there a bridge between GND and !PWRON on the ATX part?

retardware wrote:

Isn't there a bridge between GND and !PWRON on the ATX part?

That's what I think is the case, hence why I think it's always ON, but I can't see it on the photo, so I thought I would ask in case anyone has a similar adapter.

It also doesn't have the load resistor that the better adapters have in order to make sure that the voltage regulates properly. This may actually no be needed if you are using a newer power supply... but a newer power supply may also not have enough amperage on the 3.3 or 5v rail(s) depending on what kind of system you are using it for.

And you will also not get -5v with that adapter.

cyclone3d wrote:

It also doesn't have the load resistor that the better adapters have in order to make sure that the voltage regulates properly. This may actually no be needed if you are using a newer power supply... but a newer power supply may also not have enough amperage on the 3.3 or 5v rail(s) depending on what kind of system you are using it for.

And you will also not get -5v with that adapter.

I know all this, I will run them with early P4 ATX PSUs that have white -5V outs.

cyclone3d wrote:

It also doesn't have the load resistor that the better adapters have in order to make sure that the voltage regulates properly. This may actually no be needed if you are using a newer power supply... but a newer power supply may also not have enough amperage on the 3.3 or 5v rail(s) depending on what kind of system you are using it for.

What do you need a load resistor for? Powering up w/o a motherboard attached?

SirNickity wrote:

cyclone3d wrote:

It also doesn't have the load resistor that the better adapters have in order to make sure that the voltage regulates properly. This may actually no be needed if you are using a newer power supply... but a newer power supply may also not have enough amperage on the 3.3 or 5v rail(s) depending on what kind of system you are using it for.

What do you need a load resistor for? Powering up w/o a motherboard attached?

In order to make sure there is enough of a load on the 5v rail for the power supply to regulate voltage properly. And apparently some older ATX power supplies will not even power up if there isn't any draw on the 5v rail.

It really just depends on what hardware you are using. For me it is just much easier to have all my bases covered and get the adapters with the load resistor and the -5v added as well as the AT style power switch that is wired to the adapter.

Presumably you'd use such an adapter with a 286/386/486/Pentium motherboard, where pretty much everything on the board, including the CPU, is powered by the 5V rail. If anything, those retro boards should load the 5V rail more than any modern system. Unless I'm missing something?

Totally agree about the AT power switch, or at least leads that you can use to connect one. Though I guess if the price for these basic adapters was really low, might as well save the money and mod the switch to them yourself.

I do personally use that model, more expensive, but more convenient (it includes a power switch) and more secure (no risk to fry a 486 inserted in the wrong way).
https://x86.fr/atx2at-smart-converter/

CuPid wrote:

I do personally use that model, more expensive, but more convenient (it includes a power switch) and more secure (no risk to fry a 486 inserted in the wrong way).
https://x86.fr/atx2at-smart-converter/

What? Is this available now? I wanted one already a year ago! 😀 I once emailed the author, and he replied, but never heard back. Where can I buy it?

CuPid wrote:

I do personally use that model, more expensive, but more convenient (it includes a power switch) and more secure (no risk to fry a 486 inserted in the wrong way).
https://x86.fr/atx2at-smart-converter/

Very interesting. My PSUs are my main worry for my old PCs now that I replaced the drives with Compact Flash, SD card and SSDs. Problem is: most of these old PCs have uniquely shaped PSUs even if I used such a device, I would have to migrate my entire rig into an ATX case which would kill a lot of the retro appeal.

The PSU is not the only problem. Tantalum caps can fail short, and will fry traces and ICs. This device will prevent that by triggering its fuses.

root42 wrote:

The PSU is not the only problem. Tantalum caps can fail short, and will fry traces and ICs. This device will prevent that by triggering its fuses.

That's nice indeed - perhaps it would be cool if he made something similar that can be used with AT PSUs then - like be a safe guard between it and the motherboard. Most of my motherboards have no tantalum caps - just a few alu ones that show no signs of leaking or bulging and which don't really cause a lot of damage if you clean up the mess.

From what I see on pictures, it's usually off-brand motherboards that used those in spades - IBM and HP, the two brands I'm using for all my early PCs, have very few tantalums.

IBM used them a lot. Many ISA-era motherboards and cards did as well.

SirNickity wrote:

IBM used them a lot. Many ISA-era motherboards and cards did as well.

Well none of my three IBM PCs use them luckily - perhaps in other types of PCs or later models.

you can find them on ebay that also come with power switches

oeuvre wrote:

you can find them on ebay that also come with power switches

What? The smart one? Never seen it. Only the passive converters

red_avatar wrote:

CuPid wrote:

I do personally use that model, more expensive, but more convenient (it includes a power switch) and more secure (no risk to fry a 486 inserted in the wrong way).
https://x86.fr/atx2at-smart-converter/

Very interesting. My PSUs are my main worry for my old PCs now that I replaced the drives with Compact Flash, SD card and SSDs. Problem is: most of these old PCs have uniquely shaped PSUs even if I used such a device, I would have to migrate my entire rig into an ATX case which would kill a lot of the retro appeal.

@CuPid:
There is no chance of frying mobos if you memorize the simple rule: black [wires] beneath black [wires].
This way I never had such an accident in my 35 PC years.

@red_avatar:
in case overhauling the original PSUs (replacing fans and recapping if necessary) is not sufficient, you simply can replace the AT's psu board with an ATX one. Their size is usually identical. If you also replace the ATX cabling tree with the original AT one, it is even style-correct.