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I have the same MDD PowerMac3,6 as yours. I've had it from new. Apart from the loud and hot PSU, which failed once and needed recapping, it's a fine machine. I multi-boot OS9, OSX Cheetah, Panther, Tiger and Leopard plus NetBSD-9 and Debian-8. I configure yaboot from Linux for the...

There must be some variability though I've not not seen any. If you're not satisfied, get in touch with them since I know they have good customer support and returns.

Strange. I very recently installed 4 x 16MB of the OWC SIMMs in my SE/30 without issue. And I also use these in cx, ci and q700. In what way don't they fit?

CPU usage is 100% for early macOS versions. Prior to pre-emptive scheduling, most things was polled for and so the processor was always busy. macOS 8 introduced pre-emption and multi-threading among some blocking system services, but applications still needed to co-operate! It's instructive to...

My dead cache card also caused the machine to hang with a gray screen after giving a good boot chime. This card had bad tag cache SRAM chips which I successfully replaced. This 3-tone chime may indicate something else wrong with the card -- like a bad data SARM chips or the main ASIC. Since the...

I suggest subscribing to the YouTube channels of at least JDW, Mac84 and Branchus Creations, and catching up on back-issues. There's a lot of nonsense amongst the good stuff .. but much of the nonsense is good stuff too!

I've used a Beige G3 as a bridge machine. It's a popular choice which runs OSX Tiger - but also boot into Classic macOS 9.2. I use ftp or Safari to download from the web and then use AFP over AppleTalk on ethernet to send files to older machines. You need to run AppleShare 3.8.3 on the target...

Hah. On re-checking my work, I found some unconnected pins on TAG SRAM chips. My SMD soldering is flaky and I'd been so fixated with checking for bridged pins that I'd not checked for missed pins. With this fixed, the card works fine and passes its diag in MacText Pro. Victory!

Three replacement (used) Cypress chips arrived from China. All tested good on the TL866, so I installed them and plugged in the card. And the machine booted! But the cache isn't functional and, in fact, slows the machine a little. :( Usual diagnostics (like Snooper) don't seem to recognize or...

Mine's a slightly newer SyncMaster T200HD -- which is basically a TV and is fine for my PPC machines with later VGA and DVI but seems to lack coverage for graphics modes of the early Macs.

This startup circuit is relatively straightforward but prone to so many failures. After recapping a badly electrolyte-scarred board, I had a situation where things worked but the machine was left connected to power but soft-shut-down for a day or so, it would refuse to soft-start. I replaced...

I too have a non-functional Iici cache card that I'm debugging. Same failure mode at boot. It's SRAM chips are: CY7C128A-20VC 2kx8 24-pin TAG SRAM MT5C6408DJ-15 8kx8 28-pin SRAM I also have a good cache card which uses: MT5C1608DJ-20 2kx8 24-pin TAG SRAM CY7C185A-25VC 8kx8 28-pin SRAM...

I’m glad your machine checks out. There may be a dependency on the tantalums used. For the record, my misbehaving cap was a Kemet from Digikey - here’s the part info:

Oh .. and here's a recent 68kMLA post about how a reverse-polarized C22 indeed results in modem and printer port failure: https://68kmla.org/bb/index.php?threads/lc-iii-modem-port.42380/

I got the original TDK PSU back in operation; blown fuse, switching FET, current sensing resistor and opto-coupler. Here's a link to a post that includes a mostly correct schematic for the 699-0153 model which was close enough to my 699-0003 unit...

Before I flipped this cap, I measured a load of just about 0.5A on the -5V rail before the PSU tripped. After flipping, I see only 10mA. So, >0.5A being sunk by an incorrectly polarized C22 is not a good idea and it certainly exceeds the spec of both the cap and the supply. The -5V rail on the...

So I picked up an LCIII for repair. The TDK PSU was toast - caps are good but the optocoupler is open-circuit and I'm awaiting a replacement. So I bodged into service a spare Astec Beige G3 PSU and the machine booted-up fine on its aged caps. I quickly recapped with tantalums (as you do) but...

There so many ways to hork a G3 doing this stuff! I've often had to resort to an OFW init-nvram command or to pull the battery to a while! There's so many variables... but in particular: what firmware is flashed on the SATA card? what version of OpenFirmware does your bootrom have? You should...

I'd inject a word of caution here. On my SE/30, I had issues with the Rominator and BlueSCSI - so I reverted to the original ROM plus MODE32. And SE/30s can be temperamental with RAM configurations - so your mileage may vary.

Neither Beige or B&W have -5V. Here's the pinout for both: