Macintosh IIsi FlexATX Conversion Madness.

[Trash80toHP_Mini]

@blusnowkitty has posted a thread documenting his collaborative efforts with @Compgeke in developing the first version of a universal ATX to Ten-Pin-Mac conversion board. Very, very cool, props guys! :approve:



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Bodge wire fixes qualify it as a very proper prototype! :approve:

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In the IP @blusnowkitty mentioned the IIsi as the target machine of the moment and he's testing the adapter in it as pictured. So of course I jumped in with some suggestions, but I think that IIsi conversion tangent needs to be spun off. IIsi PSU modification is a special case, so to speak. Physical constraints make it the most difficult of 10-Pin Mac conversions. I've had the bits for FlexATX upgrade of my fishy IIsi PSU for I'm hot sure quite how many years sitting in the IIsi project drawer. Had some crazy plans for my particular application back when, but have rethought the project in terms of fitment to a stock IIsi with modifications made only to the PSU can. So here goes:

The PSU I have on hand should work nicely. The only mod done so far is the notch filed out of a blank area of the PCB at the front to nudge it as far forward as needed to retain the stock Power Plug/Monitor Passthru/backside of the stock can.



Here's a closeup, notice the vertically oriented stock fan, more on that later.



The PCB of the FlexATX PSU is angled down from back to front as much as possible for clearances at both ends.



Power connector has been been removed from the donor PSU, connection will be desoldered and hardwired from the front of the can for connection to the stock IIsi assembly at the rear.



Raised rear of angled PCB provides cubic for the Universal Converter and possibly more "stuff."



Here's how it looks from the rear, lots and lots of cubic available, all things considered.



Long ago I sketched the IIsi specific adapter I was planning to make using the cable connector harvested from that smelly PSU board.

Mockup of first version was made to be printed, folded and installed inside the IIsi can for visualization. PCB is mounted upside down to the lid which clears stock connector, wiring and my planned conversion board nicely. Never figured out clearance for the guide post at the that I recall? Dunno, but it's definitely a design requirement that's nicely sidestepped by the new, angled PCB approach in the pictures. Inversion of the PCB flips what would be stock FlexATX fan's intake over to the opposite side of the IIsi enclosure which keeps the retaining connector slot intact. Each side represents what is would look like if the opposite side of the box were clear.

Anyway, that's where I started, the pics are of what I'm now planning.

For the front section, I'll be fabricating some ductwork from the very thin, very inexpensive, Big Box available aluminum step flashing that anyone could make by the scoring and bending method. Using a thin profile, 10x50x50mm fan or a pair of smaller thinner fans I have on hand, all heat from the FlexATX PSU will be ducted from where it would enter the donor PSU can's fan intake and blown out what are the air intake vents of the standard IIsi PSU matching up with those on the case lid. Such will make a nice overall improvement for the heating/cooling budget of a IIsi tricked out with several PDS upgrades.

In stock form, cooling air for the IIsi PSU enters from the top vents, migrating out the can's many side panel perforations due to negative air pressure from the exhaust fan and then exits there along with all other heat produced by the system.

Dunno, off until Leftover Day, maybe I can get something accomplished. :blink:

 

[Trash80toHP_Mini]

Spent way too much time playing with the sheet metal tools today, couldn't resist. :mellow: Took a few HowTo pics of process, but not important ATM. The FlexATX PSU case is missing a lot of sheet metal now. It was the same width as the IIsi PSU can, so the sides were removed from the lid and box bottom while front and rear panels were trimmed to fit inside IIsi PSU can as well.



Overview: The only thing different from yesterday's pics would be what little remains of the FlexATX box's backside abutting the front end of the IIsi can, the trimmed bottom of the FlexATX PSU box and its trimmed front/wire harness end near the rear of the IIsi can.



Components are low enough that the stock fan could be retained, but its thickness would restrict airflow.



Bottom of the can is trimmed back to the  PCB mount, which is conveniently set back about a half of an inch from the end of the PCB.



Here you see the 10-Pin harness wiring adn the A/C wiring routed to the back end of the IIsi PSU can.



Standoffsare about 12.5mm which brings the top edge of the can't lid into contact with the underside of the lid of the IIsi PSU.



A/C lines run to back where they're to be hardwired to the harness of the stock rear end assembly.



Overview: just as there's cubic available under the backside of the angled Flex-ATX case bottom for the adapter board, there's cubic available over the lid at the front end. 



In the background you can see the air intake slots in the IIsi PSU cover. The vents in the lid of the case are shrouded by a box that likely touched the lid of the Power Supply. Plenty of room for PSU heated air to go out the top where cooling air was designed to come in.



Fugly, trial and error sheet metal work. Shoulda planned it out instead of jumping right in and winging it  .  .  . but didn't feel like it. :



Detail of top edge of FlexATX lid touching bottom of IIsi lid. The adapter PCB will probably be on a printed sled (handcrafted in my case) for access. Slack in wiring routed under the case from the front and from the IIsi plug assembly at rear provides easy access all around. Enough for now, so how about them PCBs? []

 

[Trash80toHP_Mini]

Forgot about the fan replacement. Stock fan of FlexATX PSU' are about 20mm thick, which won't work due to the height of a component underneath. 10mm and 7mm Fans will be fine installed to the Flex lid to blow straight up and out the cooling IIsi vents.





With maybe a little bit of filing I can get a 10mm thick 45mm fan to work out nicely.



Best Power Pro and a git mo just gotta go! [}]

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[Trash80toHP_Mini]

I think I may have found a winner in the fan sweepstakes! If I gang up four 30x30x7mm fans, they clear heatsink and caps by at least 3mm.

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I can mount them directly to the lid of the IIsi can under the vents above, which grid happily measures about 60x60mm. The gang of four will blow heat generated by the PSU and whatever other air is gathered from inside the case by negative pressure inside the assembly straight up and out the case's intake vents.

Mounting them 1.5mm below the metal grating and sealing the assembly will probably provide better airflow and still clear the components of my PSU by 1.5mm.

Dunno, gotta look at the CFM numbers and current draw as compared to the stock blower, we'll see!

 

[Trash80toHP_Mini]

I've begun to noodle out the same kind of conversion for the IIcx form factor PSU, not adding it here, but the pics and details are posted in the adapter development thread: