Recent content by Fizzbinn

Hmm, from your sleuthing perhaps the reason why others left off R80 as needing to be removed is that is was vestigial? The Q1 component is missing from both the LC 520 and LC 550. Its possible inter-layer connections connect R80 in a meaningful way to other components but maybe not, it seems...

I think there was some confusion, my LC 550 board is a Rev. B (820-0595-A, 4.5V PRAM battery with velcro) and @kefkafloyd 's LC 550 board is a Rev. A (820-0368-A, 3.6V 1/2 AA PRAM battery) so we have confirmed both lack all 4 resistors, although more confirmation is never a bad idea...

Really cool article, thanks for sharing! I definitely can see documentation error leading folks to think the LC 550 and CC II logic boards were substantially different when they actually aren't. I do wonder what controls the different gestalt IDs though? Macintosh LC 520 = 56 Macintosh LC 550 =...

Here you go: High Res (as I can do) front and back of my LC 550 logic board. RC67, R75, R79 and R80 not populated: For similar resolution reference my LC 520 logic board: Another thought, there are at least two versions of the LC 550/CC II logic board, one with the 3.6 Volt 1/2 AA...

LOL, Instead of spelling it out, Two-S-I, say it like it’s a word, Twosi, sounds like Tu-see, which rhymes with…

I purchased a couple of the IIsi Power Supply Replacement (Mean Well) PCB kits from CayMac Vintage a while back and wanted to post my build experience. The kit included the resistors, transistor and LED, I purchased the 4 Mean Well power supplies and the relay from Mouser: Qty 1 - IRM-60-5...

I purchased a couple of these PCB only boards from CayMac Vintage a while back and wanted to post my build experience. I ordered the required Mean Well power supplies from Mouser: IRM-10-12 (12V 0.850A) https://mou.sr/4gNUPOV IRM-20-5 (5V 4A) https://mou.sr/4mXZss7 And planned to make use...

Thanks @JDW! Annoying minimum order but seems like not a bad idea to have some of these. I purchased a programer and ROM SIMM from CayMac last year to use with my Quadra 700 but didn't think about a socket to be able to use it with my Q605 (or other future Macs I might want to try a custom ROM...

I'm failing in my searches to find a link or other pointer (part number?) to obtain one of these ROM sockets to solder in. I feel like I've seen this somewhere but would appreciate a pointer If you have one!

So I bought a boxed 520c off eBay and found it had a surprise Newer Technologies NUpowr 117MHz 603e/4MB processor upgrade card. I was mainly after the box and docs, i.e. ephemera, and as I have a 540c with a NUpowr 117MHz 603e/8MB processor upgrade card I wasn't exactly looking for one. It did...

I recall reading somewhere about someone else doing this successfully, ...and something about only specific CPU part numbers working in Macs. Was it a 5V vs 3.3V thing? https://68kmla.org/bb/index.php?threads/mc68040fe33v-source-spotted.30947/...

I see the post on the 68K forum, I was asking (likely poorly worded) the same thing as @zigzagjoe. Just change one variable at a time for a comparison. Using the v092 ROM, with everything else the same, and the CPU at the default 25MHz, changing the RAM timings from 80ns to 60ns shows this...

Very Interesting! Am I interpreting correctly, the improvement shown in the graphs is both going from 25MHz to 40MHz and enabling 60ns RAM access? If so, it would be awesome to see the difference without the overclock and just with the overclock.

"System Enabler 403" for the 520 and 550 will work. I believe the Color Classic II logic board is basically the same as the one used in the 550. These sites seems to confirm that: https://powercc.org/mystic/ https://lowendmac.com/1993/mac-colour-classic-ii/ Half the fun is figuring this stuff...

A plain 7.1 install will work on Macs that came out before it was released but you need machine specific "Enablers" in your System Folder for later Macs. Some good info on this (and Enabler downloads) here...