Power Supply for Macintosh IIsi system

Before assuming that the power supply is bad, you should consider replacing the internal 3.6-volt, ½AA lithium battery found on the motherboard. A very weak or dead one can cause startup problems, so you want to rule it out first. The battery can be purchased from a number of online vendors or from a battery specialty retail store in your area. If that doesn't solve the problem, you can always check eBay or a local Mac User Group (if any) for a used replacement P/S. If a used power supply is just a temporary measure to bridge the gap until buying a newer computer, maybe you should consider another approach. What program was used to write the sermons - (MacWrite, ClarisWorks/AppleWorks, Microsoft Word, etc.) and what OS version was the IIci running? You could always remove the internal SCSI hard drive and install it in a slightly newer (but used) Mac computer that's capable of running the program (or its PowerPC version) and opening the files. Some more info would be helpful, to provide the best advice.

brg2630,

Another option is to find an old SCSI CD-ROM drive, pull out the optical drive. Pull the SCSI drive out of the IIsi, change the SCSI id jumper to something other than zero, and put it in the external case. Then connect the case to any newer Mac with a SCSI card.

Jim

My IIci power supply has started to fail, too - I have to hold in the power button on the back for a while before it'll start up. I'll likely need to replace it sometime soon, so I'll be watching eBay for that.

If you don't have luck with that and don't have access to older hardware to swap around with, services like RetroFloppy ( http://retrofloppy.com) could be of use too.

Check this site for battery part numbers and sources. Mac PRAM, NVRAM, CUDA/PMU & Battery Tutorial

Suggest you join LEM-Swap for buying & selling Mac stuff. http://groups.google.com/group/lemswap
After you join, post a WTB (want to buy).

 Cheers, Tom 😉

I check the power supply output with a volt meter and it is dead.

I do not understand how you can say that.

Unless you have asserted the power-On signal, the supply remains mostly off until it gets a signal (from the keyboard logic) to turn on. It will appear to be dead except perhaps for Trickle Power. This feature is called "Soft Power".

The switch on the supply, if any, is merely a service switch. It does NOT turn the power supply on to full function.

Macintosh IIsi: Technical Specifications

Grant,

That was my thought, too. For all the computers and all the power supplies over the years, I have never memorized the power leads for mac soft power. Do you happen to have a quick link to the pin out for various mac power supplies?
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brg 2630,

Here is a little more detail on what Grant is saying. If you take a power supply out of a PC and notice that it does not have an on/off switch, you have to ask yourself how the power supply turns on in the first place. The green wire gets a low voltage signal from the keyboard. That signal closes a relay that starts the power supply in full. If you want to use that power supply for a science project, you can take a paper clip, bend it into a 'U' shape and poke it into the green wire pin contact and the black wire contact beside it. That is how you hot-wire a PC power supply that does not have an on/off switch - in fact, even if the supply has an on switch, you may still have to trigger the supply using the green lead. Some energy save capable supplies may even need to see a load to stay on. More on that at in the wikihow site video.

In twenty five years and hundreds of mac computers later, I do not recall ever mapping the Mac power supplies. I just swap out with another supply. So, I can not say that it is the green lead that signals a mac supply. Something new to do.

Here is a wikihow page that discusses the idea in greater detail. Notice under "tips" that they give the option for skipping a switch by connecting the green and black leads.

http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply

So, for your computer, you first need to confirm that the power supply is dead. Meanwhile, the hard drive will hopefully migrate to a more capable machine.

Jim

PS Somewhere in the last ten years is a discussion post on converting an ATX style PC power supply to work in a Mac G4 or earlier machine. That will have the pin assignments listed. Unfortunately, the machine with that book mark is a hundred miles away right now.

pps,

atx pinout:

http://pinouts.ru/Power/atxpower_pinout.shtml

http://pinouts.ru/Power/macclassicpower_pinout.shtml
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This post says that it is the white wire for a G4

http://forums.macrumors.com/showthread.php?t=261623