How to: recapping the Mega STe power supply

[Pacman]

Red Wire from the Fan to GND
Black Wire from Fan to -12V

OK. I think I've finally got it now
See new illustration below:

Noctua fan connector corrected_final_correction.png (16.63 KiB) Viewed 7418 times

[exxos]

I've gone back in this thread and updated the images. Possible we could clean up this thread in the future ?

The image looks OK to me now. GND is in effect the positive, because its at a higher potential than negative (-12v).

[Steve]

I went inside my machine to swap the fan polarity, to see if it was exhausting the air in the right direction. Now I have no power, doesn't turn on at all. Not sure what to do Measured the voltages and they fluctuate between 0-1v.

[exxos]

If the fan was running and you swapped the power, then it would have likely killed the fan.. you can't make DC fans spin backwards, they just smoke and die.

[Steve]

You think the PSU won't turn on without a working fan?

[Steve]

Okay, I think you're right. I put a new fan in and it has come to life again. Thanks Chris!

[Pacman]

I've gone back in this thread and updated the images. Possible we could clean up this thread in the future ?

The image looks OK to me now. GND is in effect the positive, because its at a higher potential than negative (-12v).

Thanks for confirming.
So the fan "+" and "-" labelling on the PCB refers to the fan wiring (connect + from the fan to + on the "Fan +" pin on the PCB and likewise for -) regardless of the actual voltage.

[Pacman]

I went inside my machine to swap the fan polarity, to see if it was exhausting the air in the right direction. Now I have no power, doesn't turn on at all. Not sure what to do Measured the voltages and they fluctuate between 0-1v.

To try this you could have flipped the fan the other way round while keeping the electrical connections the same.

[mikro]

What a great guide!

There is an error with C14 - it doesn't have + on the left on and - on the right but - on the top and + on the bottom.

Just a note, this is still wrong in the picture.

Also, when upgrading the PSU, make sure you have insulated the nut in the middle (and not used the bolt again), as mentioned in the quoted text:

Die Partnummer muss mit -002
enden. Wenn es ein -001 Netzteil ist, muß die mittlere Platinen-
Schraube entfernt werden. Außerdem muss der Stehbolzen, in den die
Schraube gedreht war, gegen die Platine isoliert werden. Klingt
zwar alles merkwürdig, ist aber tatsächlich so.

The part number must be -002
end up. If it's a -001 power supply, the middle board-
Screw are removed. In addition, the stud into which the
Screw was turned to be insulated against the board. Sounds like
everything is strange, but it is actually so.

Pacman has taken the second part about the opto-isolator but forgot to mention that this is also an important issue, as can be seen here: https://atariage.com/forums/topic/29322 ... nt-4309058

For instance, my TT is has a -002 type but interestingly, my MegaSTE (which is supposed to be younger, right?) has a -001 with the center screw installed. But since my TT is the last revision, perhaps it is younger after all, who knows.

Oh and I also tested the air flow direction, the Noctua fan must be definitely installed as shown in the picture.

[exxos]

There is an error with C14 - it doesn't have + on the left on and - on the right but - on the top and + on the bottom.

Just a note, this is still wrong in the picture.

Thanks, pacman hasn't logged in for some months so I just edited the image and uploaded it.

I will have to clean up this thread at some point...