CayMac IIsi Mean Well PSU Replacement

Fizzbinn

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Nov 29, 2021
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I purchased a couple of the IIsi Power Supply Replacement (Mean Well) PCB kits from CayMac Vintage a while back and wanted to post my build experience.

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The kit included the resistors, transistor and LED, I purchased the 4 Mean Well power supplies and the relay from Mouser:

Qty 1 - IRM-60-5 (5V 10A)

Qty 2 - IRM-10-12 (12V 0.850A)

Qty 1 - IRM-02-5 (5V 0.400A)

Qty 1 - SPDT 12A 5VDC Power PCB Relay

I used these fuse holders:

Qty 2 - Littelfuse Fuse Clips ACS PC 5MM CLIP BRASS/TIN-PLTD
https://mou.sr/48qaT8l

Here it is with logic board power cable harness and internal mains power connector (transferred from a dead original IIsi Sony PS, APS-06, 699-0567) plus the kit resistors, transistor, and LED as well as the fuse holders soldered in:

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And with the Mean Well power supplies and relay installed:

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And mostly buttoned up in the case from the dead original PS:

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On first test it seems to work just fine! ADB keyboard power-on, software shutdown, relay control of pass through power to monitor. This was in a fairly stock IIsi, 17MB RAM, slightly newer 80MB IBM SCSI HD and with the 25MHz clock crystal swap. I do want to test further with various PDS cards I have. Will report further in this thread when I get to that.

Another fun project! Perhaps a tiny bit tougher to build than the CayMac LC version of this but way easier than recapping a IIsi Sony PS. I've recapped 4 of those and it's a lot of work, the little daughter card is particularly fun. The IIsi Sony PS that I cannibalized for this was actually one I had recapped but didn't work :(, unlike the other 3 that did work and were recapped identically... Not totally sure about all the relative merits but something about pretty much all new components in the original form factor has me really liking this approach.

p.s. I also love the hidden Lucy bones that get burried under the largest Mean Well power supply. I have to admit it took me a minute to get it, IIsi, Lucy. Lucy, IIsi. POWER UP LUCY indeed!
 
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JDW

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p.s. I also love the hidden Lucy bones that get burried under the largest Mean Well power supply. I have to admit it took me a minute to get it, IIsi, Lucy. Lucy, IIsi. POWER UP LUCY indeed!
I still don't get it, but I am now strangely compelled to watch I Love Lucy episodes on YouTube.

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