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DOA G4/DA/466 = ATX shenanigans . . .

Trash80toHP_Mini

Trash80toHP_Mini

NIGHT STALKER
68040
I'm gonna cry a lot . . . :( . . . if I can't get my baby up and running again. It has been my workhorse for over twelve years now and was the last half of my original username.

Symptom:

Press Power Button = NADA! xx(

Tried re-seating most of the innards after blowing all foreign objects out of the case with my compressor.

First one was the power button board interconnect.

Next planned step is to pull out all the extra cards and HDDs for installation in the Dual Gig QS'02.

Has anyone tried shorting pins on the Power/Reset Button Board's Cable to test "Power On?"

I'm heartbroken, so I'm probably overlooking some obvious stuff, it's like a doctor working on one of his children . . . a HUGE no, no! :(

Any suggestions?

 
Power supply is dead. The non-working DA 466 I got for free was the same way. No response whatsoever from it. I took apart the supply to find 3 resistors fried...nothing else looked bad. I replaced them and all 3 fried as soon as I plugged the power cord in the wall.

 
The obvious is the PRAM battery although I think you at least get a light when they are dead. I don't know how many of those I "fixed" for people by pulling the battery out.

The actual power button boards go bad too.

That said, in all actuality it probably is the PSU at this age.

 
Thanks for the suggestion, mcd.

No joy in mudville. I thought I'd replaced the PRAM bat with one of my lot of new blue ones, but it was purple w/ green on black racing stripes. Swapped it out and blue failed too.

Just out of curiosity, which holes in the Female/PSU side of the Power Board Interconnect Cable do I stick the pins into for wiring up a momentary switch temporarily to the PSU?

I've got a BrandNIBinCellophane 400W ATX PSU on hand, but I'll need to see if I can trade up/sideways. This one was meant for a Pentium System w/LOTS of HDDs/Opticals, etc.

+5V rail is 4A shy of the DA's 20A spec.

+3.3V rail is shy of the DA'd 24A spec.

+12V1 rail is 2x DA's 8.0A spec.

+12V2 rail is 2x DA's 8.0A spec.

-12V rail is .8A vs. .25A for the DA spec.

On the ATX: what the heck is the 2.5A +5Vsb rail, Processor or VidCard Power?

On the DA what the dickens is a 4.04A +28V VS Rail? :?:

Does anyone have a suggestion for a suitable ATX PSU?

 
It's probably time to start a Hacks Topic for this . . . maybe I'll just move & re-title it . . . or clone it, it's topical right here. My buddy eeun posted this over on 'fritter:

Power Mac G4 (MDD) ATX Power Supply conversion

When the Power Button test invariably fails, I'm going to start doing a "Newt" graphic along the lines of the CC Frog graphic.

I need to do ATX conversions for:

G4 466 DA

Macintosh IIsi = just about everything from that era

Performa 6360

Radius 81/110 = 6100 etc.

DuoDocks

I might as well get 'em all set up on one big .PDF export from Illustrator.

I'm leaning toward a PCB approach for soldering the lopped off Mac harness to one side with the female end of an ATX conversion cable on the other side. If I do it that way it's a cinch to swap out another ATX PSU if the first one dies. I could hook up curbed ATX PSUs after testing or to test out physical mods of odd form factored ATX PSU guts adapted to fit into Mac PSU boxen. The PCB would be universal, small and flat, fitting into just about any case. It will have holes for standoffs so it can be mounted inside or outside just about any Mac PSU's sheet metal.

Comments/suggestions? What do you think, ojfd? :?:

 
On the ATX: what the heck is the 2.5A +5Vsb rail, Processor or VidCard Power?
On the DA what the dickens is a 4.04A +28V VS Rail? :?:
Click to expand...
Those are standby rails. You can connect the 5v of ATX to the 28V of the Mac and be able to boot(but you are not going to be using Firewire or ADC displays) but I have noticed that if you keep it that way for a long time it eventually starts having trouble cold booting. For my DA at the moment I found a 24V 4A dell notebook power adapter and wired it into my ATX extension. It has been working well but I do not have any ADC displays or bus powered FireWire devices to test it with. All I know is that it is not developing an issue overloading on cold boot like the couple other PSUs I had been swapping in and out during it's life and during hardware changes.And it is not just about quality either. One was a 650W modular Antec unit, that 650 is mostly made up by the 12V rails and the standby was seemingly not good enough for my DA I guess. :/ (this PSU went on to power a PC with crazy overclock and other fun goodies without any issue.)

The DA currently has a 350W Seasonic + the dell notebook adapter and is doing well. :)

Does anyone have a suggestion for a suitable ATX PSU?
Click to expand...
Seasonic & Corsair are loved brands. As is Antec.
 
Excellent tips, thanks, MacJunky!

I think maybe I'll put a spot on the PCB for that 4A battery/power adappter of yours, how much do they cost?

Perhaps we can coax ojfd or tomlee59 to come up with a simple circuit for the adapter PCB that'll squeeze 24V out of the two +12V rails on the ATX PSUs? That'd be a better approach . . . two batteries in series work . . . maybe with a trio of fuses, some diodes, resistors, caps and other black magic it'll work . . .

. . . or not! ::)

This is definitely turning into yet another Hacks & Development project. :approve:

 
Wow, that was fast! I got the answer I sort of expected from tomlee59.

Due to the two 12V rails sharing a common ground and coming in parallel off the same PSU, you cannot wire them in series . . . NUTS . . . }:)

Wall wart is looking the easiest to implement, but our EE tomlee59 said:

If you're up for some fun, you could buy a chip to produce a higher output from 5 or 12V. Maxim and Linear Technology both sell suitable parts (do a search for "voltage doubler" and "boost converter"; check specs to make sure they'll survive at, say, 30V or so for margin). You'll need a small handful of cheap parts to get the job done, but both companies have very good app notes to guide you
Click to expand...
I'll have to look into that one, but electron pushing isn't my strong point . . . it's a very weak point, at that. :I

Any help on that end of things would be much appreciated! :approve:

Anybody got the IIsi/IIci/Q700 etc. cable/connector pinout handy?

IIsi/IIci/Q700 Pinouts

Oh shoot, I am sorry, it is 20v.. Still good though.
Click to expand...
My Pile-o-DuoDongles are 24V! [:D] ]'>

 
You'll find my experience of the DA-ATX mod here.

Of note:

power up has been achieved, AGP video is working./

I used the +5VSB standby power (purple) lead for the +28V feed.
Click to expand...
NB: of course, this will not run an ADC monitor, or any bus-powered FW peripherals, but it will boot.

Use an ATX power extension cable for the mod.

 
Yeah, I realized my converter cable was B@$$@CKWARD$ for the task.

Since I'm doing a PCB Adapter (I LOATHE wire splicing) to simplify the hookups, I'll be looking into tomlee59's suggestion for adding a "boost converter" to the board. That way I'll get a true 28V line and I'll just leave the components for that section unpopulated for the IIsi/Q700 conversions.

 
Not to be buzz-kill-y or anything, but as cool as some sort of universal ATX-to-Apple-whatever PCB board might sound might it not be worth the trouble to just crimp together a temporary adapter and make *sure* that the problem with the G4 is the power supply? Or did that already happen and I missed it in the back-and-forth?

You don't have to actually mod the ATX supply. They sell extension cables cheaply enough. (That's what I hacked up when I did an ATX->iMac conversion.)

With regards to using a boost converter to supply your 28v, I'm somewhat skeptical that's a good idea if you intend to actually power an ADC monitor, particularly a CRT one. I don't know how many watts an ADC monitor typically pulls but I suspect it's enough that a few little components stuck on your adapter cable might be hard-pressed to handle it without some serious thought given to heat dissipation. (Judging from the commercial units for car applications/etc it's easy to find pictures of a 5 amp output 12-24v unit typically comes encased in a 3 inch square heat sink...)

 
Like I said, I've got several permutations to fab. My ADC monitors are a miniscule 17" CRT & LCD pair and I won't be running them off the DA, but the FireWire implications are important for my USB 1 ONLY OS of choice! A Duo AC Adapter Lug would make a good addition to the circuit if tomlee59's suggested parts don't pan out for FireWire.

I will be needing the 18V(?) DuoDock rail though, but that's a fairly low draw motor geared WaaayTFHeck down. }:)

 
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