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Thread: Astec PSU on Mac IIci


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Permlink Replies: 4 - Pages: 1 - Last Post: Jan 20, 2014 5:50 PM Last Post By: tt
stiv2k

Posts: 2
Registered: 1/16/14
Astec PSU on Mac IIci
Posted: Jan 16, 2014 6:59 PM
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Hi all,

I recently came into possession of a Macintosh IIci from 1989. At first, I thought "who the heck still uses this ancient hardware?" and almost threw it away. Well, who would have known there is still a community of enthusiasts for 25 year old machines. Anyways, I kept the machine and decided to restore it. I noticed the machine would boot only intermittently, and lately it does not boot at all, it just goes click click click while the keyboard lights flash. I have replaced all the large capacitors in both the power supply and the motherboard (surface mount caps are on order and will be here in a couple of days). I have read about the 5V.TRKL issue that these Astec supplies have, and have also attempted the diode remedy to no avail. I assume that since the 5V.TRKL is always outputting a clean 5V signal that this is not an issue on my supply. Does anybody know if the supply will start with no load connected? It may just be shutting itself down because there is no load (if such protection circuitry exists on this ancient thing) or that it is shutting down due to a shorted output. Any other ideas? I would love to get it working without having to replace the entire supply. Any advice would be appreciated, thanks.
bbraun


Posts: 493
Registered: 7/25/12
Re: Astec PSU on Mac IIci
Posted: Jan 16, 2014 10:36 PM   in response to: stiv2k in response to: stiv2k
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Welcome! Replacing all the surface mount tin can electrolytics is pretty much the first step in classic mac ownership these days. I'd start there and then move on to the PSU if you continue to have issues. I'm not totally sure on the IIci's PSU, but I seem to recall having manually powered on my IIx PSU by connecting the battery to the power on line.
dougg3

Posts: 190
Registered: 8/13/12
Re: Astec PSU on Mac IIci
Posted: Jan 17, 2014 1:49 AM   in response to: stiv2k in response to: stiv2k
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Hi there! I've actually had quite a bit of experience with IIcis and their power supplies. With no load connected, the power supply will constantly reboot if you try to "jump start" it, so the output voltages will be all screwed up and the fan will turn slowly. Your power supply is probably fine.

I agree with bbraun about the surface mount electrolytic capacitors on the motherboard being a potential issue. Several of them are over in the area of the power on circuit on the motherboard. Both of mine experienced intermittent power problems until I removed the old capacitors, cleaned the gunk, and soldered new ones on. Now both machines work just like they are brand new.

Good luck and be sure to let us know how it goes :-)
stiv2k

Posts: 2
Registered: 1/16/14
Re: Astec PSU on Mac IIci
Posted: Jan 20, 2014 4:23 PM   in response to: dougg3 in response to: dougg3
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Hi,

Thanks for the input. Once I got the surface mount caps in and replaced them, it's been booting up very reliably. So in the end I recapped both the PSU and the logic board. The only issue I have now is the floppy drive is not working and the video output is flickery (I think it's the VGA adapter, its in pretty bad shape).
tt


Posts: 144
Registered: 8/25/12
Re: Astec PSU on Mac IIci
Posted: Jan 20, 2014 5:50 PM   in response to: stiv2k in response to: stiv2k
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Nice work! I need to refurbish a logic board (or two) as well.

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