Additional Power Supply Question

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Last seen: 8 years 1 month ago
Joined: Jan 4 2005 - 20:47
Additional Power Supply Question

I'm sure you guys are sick of all my questions by now, but hey, just trying to get things done right. Heh! Okay, here I go:

I was able to round up a "Flex ATX Power Supply" through one of my instructors at the college. This little AC->DC power supply is considerably smaller than the standard ATX and will fit nicely in the upper cavity where the screen's located. I haven't tried it yet, but it might even fit in the hard drive bay or right behind the drive.

Before I go further I might add this, my original harness-concauction was basically the cables from the CC and 630 harness soldered together and wrapped with electrical tape - very inelegand, bulky, and caused some of the interference. After I had opened the harness to swap the IDE cable (previous post) I've discovered that crimping a new ribbon cable into the harness might now be that hard after all. Now, after a few days and many hurting fingertips later, I have created a new harness with nicely wired analogue board connector, new scsi cable etc. Looks professional, gave me more space in the Takky, and especially fixed some of the interference.

I've wired the 3.3V output into the harness and supplied the power for the hard drive with the new supply. I left everything else on the stock supply. The first nice thing I had noticed was that now won't have to "warm start" the Mac in order to get it to boot - Before I had to do the "control flower power" thing for it to actually load, now, when I hit the power key, it will come right on. Also, all the interference in sound and on the screen is gone now. I suppose that the stock power supply was simply overloaded. Now, the screen does not have *any* white lins and doesn't flicker whenever the disk is accessed (the flickering was extremely annoying).

Now, here are my questions:

1.) I've tried to i.e. replace the stock power input lines with the ones from the new supply. I had mixed results, and most of the time it actually didn't work at all. I.e. when replacing the 12V with the new supply, the system won't start up at all. With both 5V intputs replaced, it will continously reboot. It works with one 5V but the system is flakey and usually locks up during boot. I suppose there simply is no way to augment the logic board PSU to take some stress off it except for the hard drive and additional 3.3V line, unless I'm doing something wrong?

2.) Since it's an ATX PSU, the ground and green line (Power-On) need to be shorted out in order for it to become active. I've read that some of you guys have actually used an ATX supply in your Takky, therefore, I'd like to know how you have done it. Either, I permanently connect the green line and ground and hook the AC inputs to a relay like one would do with the quadra PSU, or add a DC circuit between the ground and power-on line and have it check for i.e. 5V from the analogue board so it'll open the connection between ground and green when the stock supply comes active.

Again folks, I would have never been able to take my project this far would it not have been for this forum and it's wonderful members. I really appreciate all the help and input I've gotten. Three cheers for Applefritter!


P.S.: I still haven't been ble to get the CS II NIC card to work - it worked one time and I was able to get an AppleTalk connection with my local server, but never TCP/IP. The card is detected in the system profiler and in the AppleTalk and TCP/IP control panel. The cable is fine, it worked with both the 575 and 630 boards, and my laptop. AppleTalk doesn't need any configuration, and TCP/IP is set properly to my local network. Odd eh?

Last seen: 8 years 1 month ago
Joined: Jan 4 2005 - 20:47
Update: Found a small Flex-AT

Update: Found a small Flex-ATX power supply at a reasonable price, did the mod as I suggested in the post above. I did not yet install it internally, but I was able to wire long enough cables into the CC and attached a 6-pin molex connector at both the PSU and the Takky harness so I'm able to connect it externally. Temporary fix for now but hey, the case is back on now and it works flawlessly. I have no interference on the screen whatsoever (since PSU is not overloaded anymore), no flaky 3.3V etc. Nice! The only voltage the CC still supplies to the logic board is 12V, as the system won't boot if it would be coming from the additional PSU. Everything else is supplied by the new power supply.

Regarding the 5V lines on the harness. I guess it must have been a wiring problem as I have both of the lines hooked to the new supply now and it works flawlessly now. It could actually have been the 12V line not having made proper contact with the board (I found a bent metal pin on the logic board which I fixed).

Regarding the Apple CS II Ethernet Card being a royal pain in the a**... I assumed that the PCI bus wasn't working properly because of i.e. the additional PSU, 3.3V etc. Well, I was able to find a Farallon 10/100TX CS II ethernet card (talking about hard to find!), killed all the apple extensions for ethernet installed the new drivers, plugged in the card, booted up, and it's been working flawlessly ever since. Either the Apple extensions caused compatibility issues with the old CS II card, or it's shot - it worked every now and then, but usually didn't at all - it was just a matter of luck.

Other than that, I nearly completed the project, and I'm really excited about that - thanks guys!

Last seen: 5 years 2 months ago
Joined: Dec 20 2003 - 10:38

Always good to hear of successes as well as problems! Stuart

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