mg.man
Well-known member
Didn't he correct himself and say he thought that first eBay board was actually and 8600 one.
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7500 Power Supply Woes
- Thread starter macuserman
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macuserman
Well-known member
Ah yep I totally missed that. It would make sense if there are boards from an 8600 floating around that are being sold as 7300 boards if they share the same 24pin connector.
macuserman
Well-known member
Made all the more confusing by that board on ebay having the same part number as ours though. That's the only thing that seems wonky to me.
Any chance of getting a close up on the ROM chips on teh back of the 7300. macuserman's excursion has me wondering now. I've never seen ROM chips with that set of part numbers.
mg.man
Well-known member
Sure... but not tonight... pretty jet-lagged from my trip back to the UK yesterday! I'll try tomorrow.
Actually, I think it is an 8600 because it has a 24 connector and the two large (160 pin, 208 pin?) ASICs near the center on the top (front) side of the board installed.
The 8500/8600 have all three of these ASIC positions populated, the third one being back near the battery holder.
The 7500/7600 lack the two chips in the center of the logic board, but include the one chip back near the battery holder.
The 7300 lacks the two chips in the center and also lacks the chip near the battery holder.
For whatever it's worth this is the actual listing I purchased that is claiming to be a 7600 board that has both the AV connector and a 22pin right angle connect that will be here Friday.
Apple Computer 820-0752-a Circuit Board 8200752A for sale online | eBay
Find many great new & used options and get the best deals for Apple Computer 820-0752-a Circuit Board 8200752A at the best online prices at eBay! Free shipping for many products!www.ebay.com
The board in that picture looks like a 7500 to me. But again, the two boards had exactly the same capabiliities and chipset.
It's possible I'm wrong and that the 7600 always has the 22 pin connector, but if that's the case, what difference is there between a 7500 and a 7600?
Thank you.
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macuserman
Well-known member
Very possible I got the part numbers from the wrong chips in question. So to that end here is every large chip close up on the back of my board.
I think that’s all of them.
I think that’s all of them.
Pretty sure they all have the same part number. There might be a difference when they switched from 22 pin power to 24 pin power, but the 7500 and 8500 used the same circuit board -- possible the 7600 if they are all 22 pin.
The 7300 and the original 8600 also used the same circuit board.
macuserman
Well-known member
If we can believe everymac.com 7500 and 7600 weren't sold at the same time, which means that the difference is likely just the faster processor and nothing else.
According to their site the 7500 was from August 7 1995 to April 1st 1996
And the 7600 was from April 22 1996 to November 10 1997.
mg.man
Well-known member
Thanks... I was going to ask -- I thought those were the ROMs. I'll get a pic of mine and post tomorrow.
macuserman
Well-known member
Well shoot sorry I posted the complete wrong info.
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No problem and that makes me feel better. Those are exactly the ROMs I expect to see on the 7300.
@mg.man No need for a picture of your 7300 ROMs, unless you want to take a look out of curiosity. I only care if they turn out to be something different than the 0280 - 0283 set.
And well wishes recovering from jet lag. Thank you again for carting those modules across the ocean.
Here's what I think...
Either:
1) I'm wrong and Apple didn't switch to the 24 pin connector until the 7300, or
2) Apple switched to the 24 pin connector on the 7600, but they still had stock of the 7500 board and power supply, so they shipped the old style board and PS in the 7600 case until they ran out. It wouldn't affect the customer, because there's no practical difference between the two.
Either:
1) I'm wrong and Apple didn't switch to the 24 pin connector until the 7300, or
2) Apple switched to the 24 pin connector on the 7600, but they still had stock of the 7500 board and power supply, so they shipped the old style board and PS in the 7600 case until they ran out. It wouldn't affect the customer, because there's no practical difference between the two.
macuserman
Well-known member
Sounds like we have gotten to the bottom of things, really enjoyed the discussion hope nobody minded this thread blowing up the forum.
I definitely learned a few things. Looks like the extra board I ended up ordering from ebay is indeed a 7500 or 7600 who knows which for sure, but either way it should drop right into this 7200 so I can get busy testing some accelerators I have lying around which is what started this whole thing in the first place.
macuserman
Well-known member
One last follow up on this thread, I received my ebay board today and when I went to install it the little plastic inserts that go through the holes in the board well the one nearest the power supply had to be removed, on the 7300 board there is a notch and on this board there is not. So it appears that indeed my case was for a 7300 but probably had the top cover switched on it at some point by my father. In any case other than that the board dropped right in and now my hybrid machine is up and running!
Stinkerton18
New member
While I apologize for "dead-threading", I feel it's relevant. I came across this post in trying to find a more sustainable/reliable solution for my Power Mac 7500. Your post/this thread was immensely helpful in finding the final solution but, the pin-out diagram (here: https://68kmla.org/bb/index.php?threads/7500-power-supply-woes.38781/post-419218) has a mistake.
On the 10-pin connector, the power pins are +3.3v, not 12v (confirmed with the silk screen on the original PSU's circuit board, the pinout listing here: https://pinoutguide.com/Power/Power_22_pin_MOLEX_connec_pinout.shtml, and with the silk screening on the PM's mainboard showing the socket as the "3.3v connector").
Thanks to your post as a starting point, and another blog post about someone's effors to put a Quadra into a wooden case, I made a color-coded diagram/pin mapping document here: https://docs.google.com/spreadsheets/d/1bKPddE9kDlInQ7N9fnO5qmQgvXjlHdIV0GcKRVskbZs/edit?usp=sharing. It also includes notes on a PSU On "inverter" circuit to retain the Mac's soft power function even though ATX power supplies pull the PSU ON line low instead of high/to 5v (taken from here: http://bylenga.ddns.net/index.php?page=Centris_ATX.php)
Using an EVGA 500w (Bronze rating, ick), I transplanted the ATX PSU's guts into the original PM 7500 PSU case and wired everything up. It works like a charm and I still have soft power on via the front button or keyboard power on key. Here's an internal shot (wired up fully and case rust treated), and the machine in use.
On the 10-pin connector, the power pins are +3.3v, not 12v (confirmed with the silk screen on the original PSU's circuit board, the pinout listing here: https://pinoutguide.com/Power/Power_22_pin_MOLEX_connec_pinout.shtml, and with the silk screening on the PM's mainboard showing the socket as the "3.3v connector").
Thanks to your post as a starting point, and another blog post about someone's effors to put a Quadra into a wooden case, I made a color-coded diagram/pin mapping document here: https://docs.google.com/spreadsheets/d/1bKPddE9kDlInQ7N9fnO5qmQgvXjlHdIV0GcKRVskbZs/edit?usp=sharing. It also includes notes on a PSU On "inverter" circuit to retain the Mac's soft power function even though ATX power supplies pull the PSU ON line low instead of high/to 5v (taken from here: http://bylenga.ddns.net/index.php?page=Centris_ATX.php)
Using an EVGA 500w (Bronze rating, ick), I transplanted the ATX PSU's guts into the original PM 7500 PSU case and wired everything up. It works like a charm and I still have soft power on via the front button or keyboard power on key. Here's an internal shot (wired up fully and case rust treated), and the machine in use.
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macuserman
Well-known member
Not at all this is great stuff, thank you for sharing, I was looking over your document and I had a couple of questions about it.
You list pins 4,6,21,22 on as being sources for 5V+ on the ATX PSU for the mac connector but on your ATX Pinout 22 is showing as +3.3V?
Also on some of the other pins you list 3,5,7 etc as possible sources but that doesn't seem to include all the options from the atx supply pinout you are showing that might have those, did you choose those over the other pins such as 13,15,16,17 for ground for any reason in particular or those are just the ones you picked.
On the mac side you made a note that pins 5 and 10 sense-/+ are not connected to anything but your mac side pinout shows pin 5 as ground.
Appreciate the work you put into this! Sorry for all the questions, but I just wanted to clarify a few things.
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