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| Macintosh Quadra 700 Battery Leakage | |
| Posted by: Bolle on 2019-04-25 13:34:43 U92 is the RTC/PRAM. Without it you will get exactly what you are seeing now... booting from floppy works but SCSI doesn’t + periodic blinking on connected devices. Had that before on a SE/30 with broken PRAM chip. One of the VIAs is communicating with the PRAM on bootup. If that communication fails the machine won’t boot correctly. | |
| Posted by: olePigeon on 2019-04-25 13:36:45 Sweet, thanks Bolle. Looks like you have your answer. 🙂 | |
| Posted by: AlexTheCat123 on 2019-04-25 13:45:03 Darn. I guess I won't be able to get the Quadra working after all because replacement RTC/PRAM chips seem to be pretty much impossible to find.. Thanks for all of the help! | |
| Posted by: Bolle on 2019-04-25 13:45:42 Someone really should look into how the communication between VIA and the PRAM part of the RTC/PRAM chip works. It looks a lot like I2C or something similar... Do we have the schematics for the Q700? You could wire in any RTC/PRAM from the SE through SE/30 and all other Mac II machines - they all work the same way. You also need a crystal at Y6 or Y7 if you want the time to actually advance. | |
| Posted by: AlexTheCat123 on 2019-04-25 13:48:16 Really? If that is that case, then it would be really cool if someone could program a microcontroller to emulate the PRAM chip. | |
| Posted by: olePigeon on 2019-04-25 13:48:34 @AlexTheCat123 Is there enough metal left on the chip that you can solder wires and just run some jumpers? | |
| Posted by: AlexTheCat123 on 2019-04-25 13:50:30 Unfortunately, there is not. Five or six of the pins are broken off entirely and several of the pads on the motherboard have been completely eaten away by the corrosion. | |
Posted by: Trash80toHP_Mini on 2019-04-25 13:52:33Someone really should look into how the communication between VIA and the PRAM part of the RTC/PRAM chip works.From what I recall back in the day it is indeed I2C. | |
Posted by: firebottle on 2019-05-13 07:16:11I recently bought a Macintosh Quadra 700 off of eBay (https://www.ebay.com/itm/Vintage-Apple-Macintosh-Quadra-700-M5920-Desktop-Computer-w-Harddrive-Mac-iMac/273781054522?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649) ...Strangely, this doesn't show up when you search for sold/completed auctions. Pretty sure eBay goes back at least 90 days... I searched for it today ...May 13, yours ended April 3. I've always wondered if eBay edits out auctions that don't go for big $$$ in sold/completed search results... | |
| Posted by: AlexTheCat123 on 2019-05-13 09:41:54 That is very strange. The link still works fine for me. | |
Posted by: dramirez on 2024-02-21 20:04:08Someone really should look into how the communication between VIA and the PRAM part of the RTC/PRAM chip works.Hi @Bolle, by any chance do you have the Quadra 700 schematics? Does a bad RTC will make the clock not to advance and MacTest to fail with: "One second Intrrupt Test failed"? Thank you! | |
| Posted by: theletter0xff on 2025-11-25 07:40:21 oh a second resurrection .. I also have a battery bombed Q700, the crystal oscillator at Y6 lost a leg to rust; I do not know if I will be successful grinding away the housing to solder on a jumper. It took a while to find its specs so: Y6 & Y5 Crystal Oscillator, clock xtal, 32.768Khz, smd part labeled 197S0001, 4x10x3.2 mm. I cant identify the manufacturer from the logo, but it's a similar package to the Meritek MXT7. Apple Quadra 700 Schematic; page 26, "Sound Input Circuitry & Real Time Clock"; 
Macintosh Quadra 700 & 660AV Schematics : Apple Computer Inc. : Free Download, Borrow, and Streaming : Internet ArchiveOEM Schematics for the Apple Macintosh Quadra 700 and 660AV Computers.
archive.org
@AlexTheCat123 did you get your Quadra 700 working again? | |
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