exxos's Atari, Amiga & retro forum

Hi to all,

I purchase an Atari 1040STE, when i power on the device, there is no sign of life... no led, nothing.
After unboxing the cover, i check the different voltage output, all voltages seem good except 5V.

I only have a 5V on both, can you confirm that I should have both +5V at the output of the power connection?
Is there anyone who can tell me which component(s) need to be repaired?

I have seen different new power supplies, which one would be the best if I had to replace it?

Is it possible to have a power supply with the right power supply connection?

Thank you for your help.

Best Regards.

The blue cable should be 5v and the red should be 12v. Usually it will be a blown MOSFET. But if you're unfamiliar with PSUs I would advise you just buy a new PSU as it can be dangerous. Exxos sells new PSUs in his store.

@Steve sorry to disagree but on a standard STFM power supply, 5v is red and 12v is blue. So two 5v wires, 2 grounds and one 12v.

Its a good idea to recap all psus these days due to old age and the potential damage they can cause to other components.

Oops 🤐

Yes ignore me lol. Except cautionary part.

Are you testing it under load ...

I powered up the power supply circuit using the power-on button, then I measured the different voltages directly on the connector (which connects the motherboard)

TheDark91 wrote: 06 Dec 2020 13:12 I powered up the power supply circuit using the power-on button, then I measured the different voltages directly on the connector (which connects the motherboard)

But is it plugged into the motherboard when you test ?

Got to agree with @exxos, the PSU needs to be under load in order to correctly measure the voltages, either plugged into the mainboard or a suitable load.

As @PhilC said, Red is 5v, Blue is 12v, however only 5v is required to power on the ST itself, and if you're getting 5v off load, that will drop on load and probably won't be good enough.

It sounds like the 12v side has gone bad, but because you don't know what is wrong with the PSU, whilst you could recap and replace the mosfets, if there is some other problem, you might find that even after all that, the PSU is never quite right and might fail again.

Personally I would try to repair, but in your situation, if you're not able to do that, then a replacement from exxos is good, plus there are alternatives like the Meanwell RD-50A which are cheap and easily available, but just need a bit of wiring up.

exxos wrote: 06 Dec 2020 13:53

TheDark91 wrote: 06 Dec 2020 13:12 I powered up the power supply circuit using the power-on button, then I measured the different voltages directly on the connector (which connects the motherboard)

But is it plugged into the motherboard when you test ?

No, does it was important?

TheDark91 wrote: 06 Dec 2020 16:22

exxos wrote: 06 Dec 2020 13:53

But is it plugged into the motherboard when you test ?

No, does it was important?

Yes it must be plugged in to the mainboard or on an artificial load, please read my previous post about that.