PicoRC
PicoPSU Adaptor for Macintosh SE & SE/30
| Purchase Link | Official Discord | Table of Contents |
This adaptor lets you use Pico ATX PSU in Macintosh SE and SE/30.
It replaces the original bulky and unreliable PSU, and uses very common 12V power brick instead.
Highlights
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Non-destructive and reversible
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PC fan header for more cooling
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Universal voltage with fused rails
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Low cost, efficient and reliable.
Get One / Other Stuff
Also available for Mac 128K / Plus, Apple II, and more! Check out the main page for details.
For more general-purpose diagnostics and retrofitting, check out the full-fat ATX4VC!
Table of Contents
Getting a Pico PSU
PicoPSU are tiny ATX power supplies for small PCs, but are perfect for retro computers as well.
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Official website and distributors. Even the cheapest 80W one should be plenty.
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Avoid generic clones. They over-rate and are of low quality.
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A power brick with 12V DC and center positive 5.5x2.5mm barrel jack is needed.
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They are very popular and you might already have one. Make sure it has enough wattage.
Remember that this solution is only as good as your PicoPSU and 12V Brick, so don’t skimp on them!
Kit Assembly
DON’T START YET!!! Keep reading :)
Observe the parts:
Soldering Notes
Nothing too tricky in this kit, all basic through-hole stuff.
If this is your first time, a few tips:
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Make sure your soldering iron has proper temperature control. Try your local makerspace or university lab.
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Use leaded solder and plenty of flux, temperature around 320C / 600F.
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This video covers the basics pretty well.
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Start from shortest to tallest. Solder a single pin first, and make sure the part is straight.
Assembly
Solder the main PCB as shown, follow the notes and reference photos.
The black 5x2 power connector is installed on the bottom side, make sure the notch faces the edge!
Everything else is on top side:
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Double check capacitor polarity!
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Black electrolytic cap: White stripe is NEGATIVE.
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Blue Tantalum cap: White stripe is POSITIVE.
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Yellow ceramic cap: No polarity.
Push the power switch into the plate until it clicks in place.
Make sure the hole is on top and legs faces down.
Insert into power switch PCB, make sure it sits flat and level.
Then solder it and the right-angle pin header in place.
Cleaning
This is optional, but I like to clean off the flux with 90%+ isopropyl alcohol. Submerge and scrub with a toothbrush.
Make sure it is completely dry before proceeding.
Inspection
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Compare with the reference photo and notes above. Make sure everything is in correct orientation.
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Solder joints should be shiny and smooth. If you see spikes, put on more flux and melt it again.
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There must be no solder bridges. If any, put on flux and melt it to remove.
Board Features
Install two fuses as shown below:
Fuse
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Use common car fuse RATED 5A OR LESS
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Regular, Mini, and low-profile Mini all will work. Simply push into the holder.
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DO NOT BYPASS FUSES
Power Switch
The pin header is connected to the ATX PS_ON pin.
Shorting them together turns on the PSU.
PC Fan Header
- Any standard PC fan should work
Pre-flight Checks
Use a multimeter to check for dead shorts between each power pin and GND:
If all good, plug in Pico ATX PSU, short the two pins on the switch header, and plug in 12V power.
The PSU should turn on, measure the voltage on each rail and confirm they are within spec.
Installation
We’re going to take a rather large portion of the Macintosh apart, so make sure to take plenty of photos along the way!
Snap a photo before removing a screw or unplugging a connector! It never hurts to have reference.
Remove Back Cover
⚠️Dangerous CRT voltage inside! Make sure the computer is unplugged for a few hours! Or discharge the CRT yourself.
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You’ll need a LONG Torx T15 screwdriver.
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Lay the Mac face down on a soft towel
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Loosen all the screws. Two near the ports, two in the handles.
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Take photos of which goes in where, the lower two has a thinner thread.
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Remove all the screws apart from a single one inside the handle.
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Put the screwdriver on that single loosened screw, grab the handle and try gently lifting up. The back cover should pop loose.
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Slowly lift straight up to remove the back cover.
Remove Old PSU
Further disassembly is needed to remove the old PSU.
- First, remove the screw for the green earth wire
- Remove the expansion bracket if present
- Unplug the neck board by gently lifting straight up
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Unplug the floppy and power cable from motherboard.
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DO NOT YANK STRAIGHT OUT, or you might break the CRT neck!
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Wiggle gently until loose, and carefully unplug.
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Same with power connector, unlock the latch and gently wiggle it free. Careful with the CRT neck!
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If there’s not enough space on SE/30, wait until motherboard is detached, then unplug.
- Finally, the speaker wire, same thing.
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Now you can remove the motherboard
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[Mac SE] Lift straight up along the rails.
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[SE/30] Lift up slightly, match the notch on the PCB to the notch on the right-hand-side rail, and it should release from the side.
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With motherboard out of the way, remove the 4 screws to release the drive cage
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Careful with CRT neck while lifting it out!
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Unplug the Molex connector and 14-pin power connector
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Now we have enough room to remove the build-in PSU!
- Remove the PSU screws, support it with your hand so it doesn’t fall over.
- Try rotate the PSU free, unplug, and remove. Careful not to bump into CRT glass.
That’s it! The main culprit is out!
While You’re Here…
With everything apart, it might be a good idea to perform some maintenance.
Ideas include:
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Check motherboard for corrosion and leakage
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Re-cap the motherboard if not already done
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Check analog board for cracked solder joints
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General cleaning / blow out dust
Install PicoPSU
With maintenance done, time to install the new PSU!
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Insert two screws into the mounting holes near the edge, then install the standoffs from the other side
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Use 5mm socket bit to tighten.
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Plug PicoPSU into ATX connector
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Use jumper wire to connect the header between two PCBs
- Undo the locking ring on the barrel jack, insert through the hole, reinstall the ring to fix it in place.
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Plug the adaptor into the analog board as shown
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Make sure connector is lined up (NOT OFF-BY-ONE), and push firmly so it’s all the way in.
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Install the power switch PCB on the standoffs, and install two more standoffs to hold in place.
- That’s it! You’re done!
Putting it Back Together
Time to put everything back! Pretty much the opposite of disassembly!
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Careful with CRT neck AT ALL TIMES!
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Plug Molex and motherboard power connector back into analog board
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Reinstall drive cage
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Reinstall motherboard
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Plug in speaker wire, power connector, SCSI and floppy cable.
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Reinstall CRT neck board
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(If present) Reinstall expansion bracket
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Double check for short circuit if you want
If everything checks out, take a breath, plug it in and turn it on.
If your Mac was working before, hopefully it still does!
If the Mac is of unknown condition, now you’ll find out!
And if it doesn’t work, check out the troubleshooting guide.
Adding a Fan
There’s already a fan inside Mac SE, but you can add another one or replace it.
Any regular PC fan should work.
Make sure the fan is secured, nothing touches the blade, and air flow direction is correct.
Don’t mount the fan too close to the CRT, or the picture might wobble from the motor’s magnetic field.
Blanking Plate
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Pull apart the nylon rivets
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Insert the “hollow tube” into a blanking plate
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Cover the hole from outside, then the other plate from inside, make sure the tube goes through both.
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Insert the “plunger” to fasten it together.
Congratulations!
Put the rear shell back on (don’t forget the paper insulation over the motherboard!), and you’re done!
With the new PSU, a fresh maintenance, and upgraded cooling, your Mac should continue to provide entertainment for years to come!
What’s with the wireless keyboard and mouse? Check out USB4VC!
Troubleshooting
This adaptor eliminates the PSU from the equation, but that’s only part of the puzzle!
If something else is wrong, you still need to fix it.
Nothing Happens / Garbled Screen
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Look for corrosion from battery / capacitor leakage on the motherboard.
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Mac SE/30 WILL have leaking caps, and you’ll need to recap before it will work.
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Check for blown fuse, or shorts on power rails.
CRT Geometry Messed Up
I had this happen with a knock-off generic PicoPSU, changing to another one fixed it.
Screen Wobbles
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If it happens when floppy drive is active, try using a beefier power brick, or add more decoupling capacitors.
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If happens while idle, make sure the fan is not too close to the CRT.
Other Failures
Other common issues include:
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Cracked solder joints
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Dirty contacts / Bad RAMs
I highly recommend watching Adrian’s Digital Basement Macintosh Repair-a-thon, where he covers a lot of those in detail.
The power connector and CRT deflection capacitors are notorious for cracking, here are some examples on mine:
It might be very difficult to see with naked eye, so use magnification!
Flux + new solder should fix it right up, if you find one crack might as well do the whole row.
Questions or Comments?
Feel free to ask in official Discord Chatroom, raise a Github issue, or email dekunukem gmail.com!