Atari STE - Issues with power connector (J302)

[rubber_jonnie]

@HigashiJun Great, let us know what the outcome is.

[HigashiJun]

Ok, so I've managed to take the eyelet off and as expected there's no spark any more bouncing on the PCB.

(Thanks to your great help !)

However, the machine still doesn't boot.

Just to be sure, is the +5V pin working the same way as the +12v one (ie. +5v fed on one side) ? If so, I will then have to get rid of the eyelet in the through hole...

Cheers.

[rubber_jonnie]

No, the 5v is fed from the track you can see coming from the main power connector on the top of the board so leave that alone. It sounds like there's something else going on.

I've annotated your diagram to show the position of the feeds from the main PSU connector.

Red is 5v, the leftmost two pins. The PCB track is on top of the board. If you remove this via and there is a another connection on the bottom, you'll have problems. Even if there is no connection on the bottom, these are soldered from the bottom so removing the via means you won't be able to solder anything in.

Yellow is ground, 3 pins on the PSU connector, (GND) and it is a large plane, also on the top of the board. If you remove these vias and there is a another connection on the bottom, you'll have problems. Even if there is no connection on the bottom, these are soldered from the bottom so removing the via means you won't be able to solder anything in.

Blue is 12v, the single pin on the right hand side. It starts of on the top of the board and the PCB track goes to point A. It then goes down to the bottom of the board through a via, and then underneath to point B, where the via you removed was. Since the via at point B is gone, but the PCB track is still on the bottom, that's ok, you can still solder to the track.

Don't remove any of the other vias or you'll compromise the power connection.

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[HigashiJun]

Thank you for your confirmation rubber_jonnie, that's what I wanted to hear.

I will have to check further if time allows...

[rubber_jonnie]

Thank you for your confirmation rubber_jonnie, that's what I wanted to hear.

I will have to check further if time allows...

You may want to go bck to my last post, as I've updated it slightly.

[tzok]

STe should boot just fine without 12V. STe floppies used in STes don't use it, and even if you'd cut it completely off from the PSU, just the composite video/TV out would be non-functional.

[rubber_jonnie]

STe should boot just fine without 12V. STe floppies used in STes don't use it, and even if you'd cut it completely off from the PSU, just the composite video/TV out would be non-functional.

Quite right, there ins't much that needs 12v, and 12v is definitely not required to boot. When I was first getting my 520ST going and had no external PSU, I just hooked everything up to 5v and had no problems.

[exxos]

STe should boot just fine without 12V. STe floppies used in STes don't use it, and even if you'd cut it completely off from the PSU, just the composite video/TV out would be non-functional.

Part of the STe audio circuit uses 12V as well.

[HigashiJun]

Thank you all for this precious information !

I didn't know the +12v is used in the Atari STE. I thought it was just a remaining from old times for power hungry FDD drives.

I made some connection tests with my multimeter and everything seems alright, so there must be something else I missed somewhere.

Just my own opinion, but this power connector is quite "special". I have repaired many Orics, Amstrads and Amigas MB and I never had such weird issues...

[tzok]

Yet, computer should boot just fine, without it.