How to mod an ATX PSU for 10 Pin Macintosh (for example IIsi, IIci, Quadra 700 and others)

[superjer2000]

OK, I want to study this a bit more but I believe this is the setup required.  Referencing the diagram on the right:

1. PFW would connect to pin 9 on the motherboard.  

2. +5V would connect to +5V VSB on the ATX PSU

3. PS ON would connect to Pin 14 (PS-ON) of the ATX PSU.

4. The 74LS04N still needs power (5vsb) + GND connected to appropriate pins.

5. I'm assuming small 1/4 watt resistors will work here but i don't know for sure.

When PFW is low (i.e. near 0V) that means output 2 of the 74LS04N inverter is high (~5V).  That prevents is fed to the ATX PSU PS ON pin keeping the unit from turning on.

When PFW goes high (i.e. near 5V) when soft power is pressed, that causes output 2 of the inverter to be pulled low so PS ON voltage is close enough to zero as to let the ATX PSU turn on.

 

[Von]

THx for this @superjer2000. There is a daughter card that can be seen on the left side of both of my last photos. I wonder if that board could be salvaged and used for what you describe.

 

[superjer2000]

THx for this @superjer2000. There is a daughter card that can be seen on the left side of both of my last photos. I wonder if that board could be salvaged and used for what you describe.

I'd be curious to know how guys like @IlikeTech did it.  I was thinking of putting this on a small breadboard cut down to the size of the components (should be quite small) and then wrapping them with electrical tape and mounting inside the PSU.

 

[superjer2000]

OK, I want to study this a bit more but I believe this is the setup required.  Referencing the diagram on the right:

1. PFW would connect to pin 9 on the motherboard.  

2. +5V would connect to +5V VSB on the ATX PSU

3. PS ON would connect to Pin 14 (PS-ON) of the ATX PSU.

4. The 74LS04N still needs power (5vsb) + GND connected to appropriate pins.

5. I'm assuming small 1/4 watt resistors will work here but i don't know for sure.

When PFW is low (i.e. near 0V) that means output 2 of the 74LS04N inverter is high (~5V).  That prevents is fed to the ATX PSU PS ON pin keeping the unit from turning on.

When PFW goes high (i.e. near 5V) when soft power is pressed, that causes output 2 of the inverter to be pulled low so PS ON voltage is close enough to zero as to let the ATX PSU turn on.

I went back and am confident in the above configuration.  I think the 1k resistors will work fine and small resistors will easily deal with the amount of current going through them.  I'm going to try to put a Seasonic into a IIci/IIcx power supply and will try to order a 74LS04 (or pick up a few at Frys) and give this a shot in the next couple of weeks.

 

[Von]

Good news...the SeaSonic fired up the fully loaded IIsi without issue.  IIsi PS chassis is gutted other than the wires in from the SeaSonic.  I left the green PS ON in its ATX location and jumpered it to ground (you can just see the "U" made with white wire):



I have the PS plugged into my PowerKey switch for my SE/30 and it is then plugged into a switchable strip.  When I power the strip, I can turn the IIsi on with the ADB KB Power button.  When I try and shut down, I need to hit the switch on the the strip.  I do not have the init installed for the PowerKey and I don't know whether it will work here.

I ran the IIsi for about 30 minutes and the picture looked better than it ever had. It used to have a slight flicker on the 15 inch LCD. Now it is rock solid.

The SeaSonic fan turned once when powered on however I did not see it spin while I used it tonight. I will keep my eye on it...

I'm going to try to put a Seasonic into a IIci/IIcx power supply and will try to order a 74LS04 (or pick up a few at Frys) and give this a shot in the next couple of weeks.

I am looking forward to seeing your progress on the circuit. I will likely follow your lead.

 

[Von]

I spent a bit more time with this.  I didn't have enough standoffs so to mock this up, I used a piece os ABS plastic and riveted it using the stock standoffs:



The 3 holes in the plastic are where the PS will be attached to the plastic.  The SeaSonic power connection slots into the stock chassis nicely.

Here is the PS screwed into the ABS plastic, notice that it hangs over where the wires exit the chassis to join the mother board.



For now, I just have the fan secured with craft double stick tape.  When it comes time for final assembly, I will use some very sticky 3M automotive trim double stick tape.



 And here it is installed and running:



All unused wires have been removed from the PS and the green PS-ON is grounded in a now-unoccupied ground position. I plan to keep the 4=pin connector to power the hard drive and fan. These will feed through a hole in the chassis cover.  There is plenty of room to put the chassis cover on, however, I'll do that after the soft power circuit gets built. FWIW, with the PowerKey init installed, it does truly shut the machine down as it does with my SE/30 which does not have soft power.

After running the in the configuration shown (nothing in the PDS slot, stock video, and IDE SSD+Acard SCSI-to-IDE bridge) the fan kicked on and ran continuously.  It has been in the low 80's in the Seattle area so it was hot in the office. While I have no way to measure how hot the PS was, those 3 silver grids were quite hot to the touch.

Yes, going this route will lose the plug for the monitor however I never had an Apple monitor, just my Envision LCD...

 

[superjer2000]

@Von I don't know for sure but a few PSUs I've taken apart have indicated the heat sinks can be live so may not want to touch to check temps.

When you say you lose the plug for the monitor, what do you mean?

 

[Von]

Being that there were no instructions in the SeaSonic box, I was careful when approaching the heatsink.  I was pretty sure I'd be OK as the heatsinks all come in contact with the top of the SeaSonic chassis. 

As to what is missing...



Above is the back of the stock IIsi PS. When I put the SeaSonic in the IIsi chassis, the power plug from the wall goes in the male connector on the left. The fitting on the right is not used and that is where the fan blows out. I believe it is for the monitor so that it will turn on with the IIsi soft power. I never had that power cord for my IIsi.  I don't feel this is a big loss as that fan needs somewhere to vent the heat and that opening will work nicely.

This is what it looks like from the back of the IIsi case outside looking in...

 

[CC_333]

Nice work!

If I were doing this (and I might!), I'd probably take the connectors from the old PSU and wire them up to the new one because I'm very particular about aesthetics, and I like mods like this to look as close to stock as possible. It's extra work, but it looks much better in the long run.

Here's a little side story to illustrate my point: I recently did this to an HP Pavilion 5040 I've had for about 12 years. Well, I did it about 11 years ago when the stock power supply died, but I redid it recently so that I could make it safe and proper (it finally has an on/off switch again!). When I did it he first time, I simply unscrewed the monitor port and chipped away the mounting ears, so I could push it into the PSU enclosure far enough to let the thing fit properly. Obviously this isn't safe, but it worked. I could've modded the computer by cutting a hole for the extraneous port (it would be a useful feature, in this context), but I didn't want to damage it, plus there's a plastic trim piece that covers it up, and I'd have to cut a hole in that as well, and since this is not a replaceable part, I didn't want to risk ruining it.

Fast forward to this year, and I decided that I should finally fix this properly, so I ended up actually removing the plug altogether, now that my soldering skills are 1000% better than they were.

So, anyway, this is an example of the opposite situation, which is a case of modding the PSU to fit the computer, rather than modding the computer to fit the PSU. The end result, however, is the same: it looks 100% stock from the outside, thereby maintaining the aesthetics of the computer.

c

 

[Von]

...I'd probably take the connectors from the old PSU and wire them up to the new one because...

I thought about that too. While certainly doable,  I think there'd be a bit of work to get it functioning like the stock PS. I suspect that the power socket for the monitor is not hot until soft power is enabled.  I don't know how to wire that up. As to the fan...that probably could go at the other end of the PS chassis and blow on to the innards.  This is still a work in progress...

 

[CC_333]

Hmm. I'd probably wire it in series with the main power in socket, so it's always hot. It probably diminishes it's usefulness a bit, but it wouldn't be a load on the PSU itself, then. EDIT: You could wire a relay in, which will engage and supply power to the monitor socket when the PSU is powered on. Perhaps one of those relays that switch AC, but whose contacts are energized via a 12VDC current? Probably more work thatn it's worth, especially if you'll never use it (there does exist an adapter that basically takes that monitor socket and turns it into a regular mains plug (I actually have one, somewhere...), allowing one to plug anything into it without needing a special cable, so that might be worth considering?)

Works in progress are fun to tinker with! My Sandy Bridge PC is such a project. I'm always tweaking it (my latest bit of work on it involved dremelling out the fan grille on the back (it's designed as a late-model AT/early ATX case (it's beige )*.

The fan works much better now. Next step is to do the same for the front grille (behind the front panel) so air can come in as easily as it goes out.

c

*Why not get a more modern case with better cooling? Well, I could, but I really like the aesthetics of this case (it's mid-90s NOS, so it hasn't yellowed like so many used ones have (alas, it will yellow eventually now that I'm actively using it, but there are ways of preventing slowing down the yellowing process nowadays, so I'm not *too* concerned about it).

 

[superjer2000]

I started the process of retrofitting a Seasonic into a IIci/IIcx PSU and built and tested the soft power on circuit.  I ended up just using a transistor and two resistors to create the inverter switch (When input is +5v, the output is low and vice-versa.  As the Mac sends +5V when the keyboard power on button is pressed, the inverter makes the output low which triggers the ATX power supply.)

The circuit I used is from https://electronicsclub.info/transistorcircuits.htm (Search for inverter).  I used a PN2222 transistor that I had from an old Sparkfun kit I had laying around.  I used the resistor values from the electronicsclub in the circuit.

I first laid everything out on a breadboard to make sure it worked fine with the ATX supply.  The red wire was connected to the power supply +5V standby.  The black wire connected to ground.  The yellow wire connected to the ATX power supply green wire (PS_ON).   The blue wire is the trigger wire that turns on the ATX supply when connected to +5V.  When the blue wire was connected to the +5V standby the power supply turned on as expected.



I then re-laid the components out on a small cut-out PCB as follows.



The side with three wires connects to the Seasonic power supply output.  (Black = Ground (Black on Seasonic), Purple = +5V Standby (Purple on Seasonic), Orange = ATX PWR_ON (Green on Seasonic).

The side with the two wires connects to the 10 pin connector that plugs into the Mac motherboard.  (Purple to pin 10 of Iici Mother board connector, Yellow to Pin 9 of Motherboard connector).



I then used shrink-wrap tubing to cover up the circuit board and then added it to my connector (between the Seasonic and test 10-pin Iici plug)





I tested it on my IIcx and it powered up from the keyboard perfectly.  Next step is to mount the Seasonic inside the PSU case.  The only issue I just realized is that the Antec supply in my Iici provides 1.0A on -12V whereas the Seasonic is only 0.8A.  I don't expect I'll have any issues I've seen a number of posts indicating the IIvi supply is compatible and that only puts out 0.6A.

 

[Von]

@superjer2000 exceptional work and exceptional timing. I will follow your lead when time allows.

Here is the progress I made today on getting this running in my IIsi.  I had mocked up the fit with a piece of ABS plastic however I was concerned that the board was not grounded to the chassis.  This is the bottom of the SeaSonic:



3 of the 4 mounting points look like they were grounded to the chassis so I created a harness to do this so that I didn't need to drill any holes into the IIsi PS chassis.  

This is the grounding harness next to the ABS:



The harness goes under the ABS next to the bottom of the chassis:



Above is a pop rivet about to be set in one of the existing IIsi PS chassis standoff/risers.

Here is the harness with crimp-ons bent to 90 degrees so everything will fit:



I hot glued some washers to the ABS to ensure crimp-on O would have good contact to the bottom of the SeaSonic:



In above photo, bottom right corner of the SeaSonic does not have ABS underneath it so it just has a screw screwed into a riser with its male thread post filed off.

This is where power enters and it is surrounded by the metal that is secured to the floor of the SeaSonic chassis. In the IIsi chassis, the plug is rotated 90 degrees and I riveted a male tab through the mounting hole and covered the bottom with hot glue for a bit of extra protection from it shorting something:



And here is the plug installed in the IIsi chassis with a female crimp-on as the last connection on the grounding harness:



THe fan is now installed with automotive trim double-stick tape and it is not going anywhere.

Here is the unit installed showing the 4-pin molex exiting the chassis cover and powering my IDE SSD:



I let it run for about 3 hour and I put a bit of a streamer on the back side of the case to see fan activity.  It came on after about 15 minutes and appeared to run the entire 3 hours.  I left several times and it was always blowing when I returned. When I touched the top of the case it was barely warm.

Next step is to build that circuit!

 

[trag]

Looks like fun stuff.   Surface mount inverters are $.36 at DigiKey.   So, if one were inclined to run off a few boards at Seed Studios, one could probably make little Macintosh PS converter boards for board cost + $.50...

 

[MrGasS27]

View attachment 24471





 





3

How do you attached the IDE drive to the SCSI controller? Is that board an IDE to SCSI?

 

[Trash80toHP_Mini]

That IIsi ATX conversion is a thing of beauty, Von.  Especially love the cooling fan setup. Haven't been following this thread, now I'll have to study it closely!

 

[superjer2000]

I finished retrofitting a Seasonic into a IIci/IIcx power supply (Antec) case.  Compared to the SE/30 retrofit, this was a lot more work as:

1) The wires from the power plug to the power supply board aren't nearly long enough for the IIci PSU case so I needed to splice in extensions.

2) The power plug hole in the PSU sheet metal case was about 1mm to small so I needed to Dremel it out a bit so I could push the plug into the case.

@Von Like I did for the SE/30, I used standoffs to mount the PSU in the IIci PSU case, but when I was doing my final tests, I realized that only 1 of the four mounting points on the Seasonic are tied into the PSU's ground.  You built a grounding harness that covers all four points, but something to keep in mind for future projects as I only used three standoffs to mount my PSU board so it could clear the 10 pin power connector that exits at the bottom and I needed to reorient my board so the one mounting point was making contact with the chassis.  (Three mounting points are ringed with metal oddly enough though).

I took this opportunity to replace the stock fan with a Noctua 80mm fan.  Although I haven't had much success with Noctua before, for this purpose it puts out way more than enough air and is really quiet.  I plugged the Noctua directly into the Seasonic power plug so it is always on.  It's quiet enough you wouldn't notice it.

The power on transistor circuit works perfect.  Overall, I'm still very pleased with this mod even though it was more work that I though it was going to be.  It's neat how much smaller this PSU is than the unit that was in the case before.  A few pics are attached.

 

[Von]

How do you attached the IDE drive to the SCSI controller? Is that board an IDE to SCSI?

Acard AEC 7720U card is what is shown.  Here is what is available on Ebay

At some point I'd like to do a bake-off between that card and my SCSI SSDs when time allows...

@Von Like I did for the SE/30, I used standoffs to mount the PSU in the IIci PSU case, but when I was doing my final tests, I realized that only 1 of the four mounting points on the Seasonic are tied into the PSU's ground.  You built a grounding harness that covers all four points, but something to keep in mind for future projects as I only used three standoffs to mount my PSU board so it could clear the 10 pin power connector that exits at the bottom and I needed to reorient my board so the one mounting point was making contact with the chassis.  (Three mounting points are ringed with metal oddly enough though).

Great progress on conversion and thx again for the how-to on the circuit.

I am trying to follow along with your comment about grounding.  The stock SeaSonic has ground enter the chassis from the power plug which has the ground wire grounded to the chassis with that metal bracket that surrounds the power plug on 3 sides and is screwed to the chassis with one of the 5 screws in the bottom. The other 4 points where the SeaSonic board mounts to the chassis are the remaining 4 screws that go into the stock standoffs.  Of those 4 mounting points, 3 appear like they should be ground as there is metal, that would be top left and both on the bottom of this photo:

This is the bottom of the SeaSonic:

View attachment 24520

What my harness did was ground those 3 points along with the power plug.  Are you saying that only one of the 3 with metal is actually needed to ground the board?  I did not test this, I just mimicked the stock setup which may have been overkill.

 

[superjer2000]

@Von Your last comment is correct - as far as I can tell, only one of those 3 metal ringed mounting holes seemed to tie into the PSU ground.  After I had my PSU mounted in my case, I was checking for continuity between the ATX connector ground pins and the metal power supply chassis and I didn't have any.  I pulled the PSU out and tested the ground pins against those three metal ringed mounting holes, and only one had continuity.  I think it was the one in the top left of your picture.  The bottom right hole seems to also have something connected to it (the two through hole pins), it looks like it might be the two little blue caps.  I then turned my PSU mounting 180-degrees and I then had continuity between the ATX connector ground pins and the metal chassis.

Looking at my pics again, it looks like that fourth hole I didn't mount to the chassis is that hole that is on the bottom right of your picture, so I might need to go back and hook up a ground wire from there to the power supply chassis.

 

[Von]

I started the process of retrofitting a Seasonic into a IIci/IIcx PSU and built and tested the soft power on circuit.  I ended up just using a transistor and two resistors to create the inverter switch (When input is +5v, the output is low and vice-versa.  As the Mac sends +5V when the keyboard power on button is pressed, the inverter makes the output low which triggers the ATX power supply.)

The circuit I used is from https://electronicsclub.info/transistorcircuits.htm (Search for inverter).  I used a PN2222 transistor that I had from an old Sparkfun kit I had laying around.  I used the resistor values from the electronicsclub in the circuit.



I first laid everything out on a breadboard to make sure it worked fine with the ATX supply.  The red wire was connected to the power supply +5V standby.  The black wire connected to ground.  The yellow wire connected to the ATX power supply green wire (PS_ON).   The blue wire is the trigger wire that turns on the ATX supply when connected to +5V.  When the blue wire was connected to the +5V standby the power supply turned on as expected.

View attachment 24512

I then re-laid the components out on a small cut-out PCB as follows.

View attachment 24513

The side with three wires connects to the Seasonic power supply output.  (Black = Ground (Black on Seasonic), Purple = +5V Standby (Purple on Seasonic), Orange = ATX PWR_ON (Green on Seasonic).

The side with the two wires connects to the 10 pin connector that plugs into the Mac motherboard.  (Purple to pin 10 of Iici Mother board connector, Yellow to Pin 9 of Motherboard connector).

View attachment 24514

I then used shrink-wrap tubing to cover up the circuit board and then added it to my connector (between the Seasonic and test 10-pin Iici plug)

View attachment 24515

View attachment 24516

I tested it on my IIcx and it powered up from the keyboard perfectly.  Next step is to mount the Seasonic inside the PSU case.  The only issue I just realized is that the Antec supply in my Iici provides 1.0A on -12V whereas the Seasonic is only 0.8A.  I don't expect I'll have any issues I've seen a number of posts indicating the IIvi supply is compatible and that only puts out 0.6A.

Hey @superjer2000 I am about to go shopping and make a couple of these and I tried to stitch everything together and I have a question for you on your final assembly.



Could you take a look at what this and LMK if I interpreted your connections correctly and LMK what that center connection is?

THx!