68kMLA Classic Interface
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| Macintosh SE/30 logicboard recreation (thread revival) | |
| Posted by: robin-fo on 2022-04-08 10:47:08 Well spotted, @Garrett B ! Well I totally forgot about this chip… It lost two legs during removal (no recovery feasible) and I sometimes wired up a Classic‘s RTC for testing. I also tried to program an ATtiny, but this was not yet successful as I couldn‘t measure the 1Hz pulse. Maybe you only need the chip for booting the OS? I hope to report some more progress in a few days… | |
| Posted by: daanvdl on 2022-04-09 06:40:45 Anyone know a replacement for RP9? (Bourne 4816P-002-201) It doesn’t seems to be available anywhere:-( This is a resistor network (200ohm bussed). Most likely used for pull-up, but not sure if I can replace it for a (f.e) 220ohm bussed network.. | |
| Posted by: mg.man on 2022-04-09 07:24:41 You might want to check this out... 
Bourns Again - Bourns 601 Series RC Network T-Filters ReplacementGithub Project Link: Bourns-601-Series-RC-Network-T-Filters This is a recreation the discontinued Bourns 4120R-601-250/201 DIP used on the Macintosh SE and Macintosh SE/30. The filter chip also goes by the model numbers M/C 8908L 115-0002, CRL 8743L 115-0002 or P9120M115-0006. Pictures of...
tinkerdifferent.com
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Posted by: daanvdl on 2022-04-09 11:33:06You might want to check this out...Unfortunately is this for the 601 series, RP9 is a 4800P Series SOC16 :-( | |
| Posted by: mg.man on 2022-04-09 12:37:41 Ah, sorry. The original seems to be available - if you order 2000!! A 220 Ohm alternative may work - the key will be the internal layout and mapping to the pins. Found this - https://www.digikey.co.uk/en/products/detail/bourns-inc/4816P-T02-221LF/1089338 | |
| Posted by: Bolle on 2022-04-09 13:33:22 Anything will work there. I’ve got a 1k network on there on one board and it’s just fine. | |
Posted by: daanvdl on 2022-04-09 13:54:11Anything will work there. I’ve got a 1k network on there on one board and it’s just fine.Thanks Bolle 🙏 What is the purpose of this network? | |
Posted by: robin-fo on 2022-04-12 14:03:02Anyone know a replacement for RP9? (Bourne 4816P-002-201)I'm using this one: https://www.mouser.ch/ProductDetail/652-4816P-2LF-220 | |
Posted by: robin-fo on 2022-04-12 14:06:28Nice work! I'm sure that was a great feeling to see it boot after troubleshooting.It turned out that the RTC chip is indeed required. Without it, you just get a blinking question mark even if there is a working hard drive connected. Using the RTC chip of a Mac Classic, I was able to successfully boot into System 7.1! 😍 | |
Posted by: daanvdl on 2022-04-15 06:13:08It turned out that the RTC chip is indeed required. Without it, you just get a blinking question mark even if there is a working hard drive connected. Using the RTC chip of a Mac Classic, I was able to successfully boot into System 7.1! 😍Hi Robin, How did you connect the PLCC20 RTC chip from the Classic to the DIP8 on the SE30 board? Regards, Daan | |
Posted by: robin-fo on 2022-04-16 11:34:53Hi Robin,Hi Daan I soldered some jumper wires to the relevant pins on the Classic‘s RTC chip and plugged them into the corresponding places on the DIP socket on the logic board. This is, of course, no permanent solution, but currently the only way to boot the machine. | |
| Posted by: PacificState on 2022-04-18 21:58:54 Thanks again to Bolle for putting all the work in here. I have a bit of a problem, though - I moved components from a damaged board over to a new board I ordered from JLCPCB with the bottom side preassembled (minus the inductors, which I shifted over), and all I'm finally greeted with are horizontal black and white bars. I've rechecked the board multiple times, assuming that this is a bad solder joint, but I can't seem to identify the problem. I've also verified all the chips and caps (which are all new), and in particular eyeballed all the SIMM soldering - but can't see anything wrong. I've attached a couple of pictures - did I miss anything? Otherwise, is there a good way to track this down? | |
| Posted by: robin-fo on 2022-04-18 23:01:56 Had the same problem. It turned out that the RAM itself was the issue. | |
| Posted by: PacificState on 2022-04-18 23:22:06 Thanks! In this case, it's not RAM per se - I've swapped it out (to just 4 x 1MB with SIMMS that worked the last time I tried them) along with the ROM SIMM. I'm a bit stumped - is there any way to check the boot process? I have a scope and a logic analyzer... Edit: there's also no boot chime, although I hear what sounds like a normal slight 'pop' as the system turns on - so I assume the 68030 isn't getting to run code. | |
| Posted by: PacificState on 2022-04-19 13:37:58 Hmmm - can someone talk me through the reset circuit? I notice that: - UB11 has 12V at pins 11 and 12, but pin 13 drops from 12V without the chip inserted, to ~1.6V with it present. 5V is there, too. - Pin 5 (reset) seems stuck at 5V The IC pins do seem rather corroded - could the chip(s - I've swapped them) be at fault, or could something else be pulling down the rail / otherwise affecting reset? | |
| Posted by: PacificState on 2022-04-19 19:09:37 Hmm - I'm actually stumped: - I think the reset pin is active low, and so *meant* to be at 5V steady state; I see it toggle on the scope after a reset - Clocks and reset are going into both the 68030 and the Glue chip What I don't see (with the scope) after hitting the reset button each time is any activity on either the 68030 address/data lines or the ROM pin of the Glue chip. Can anyone suggest next steps? | |
| Posted by: PacificState on 2022-04-23 13:15:05 Got past that issue - there was a *tiny* blob of solder between the vias. With that clear, I get to a boot chime - but then (with a Rominator installed) the sad rising boot chimes and Simasimac. The RAM boots in another board, the muxes (and caps!) are all new parts, I can't see any other obvious shorts, and I've been tracing out the lines and buses for the last few nights without success. I'm pretty sure this is a RAM init error - any other suggestions other than to keep tracing? | |
| Posted by: robin-fo on 2022-04-24 06:00:26 During the absence of a working RTC chip, I had a similar scenario with the Rominator installed: Boot chime and shortly after that a sad mac screen with death chime. With the original ROM installed however, it booted straight to the blinking question mark (but not further due to the absence of the RTC). I don‘t know if this was a similar issue as yours, but I suggest trying with a stock ROM. | |
| Posted by: PacificState on 2022-04-24 11:19:22 Thanks! I’ve resorted to A/B this board with a known good one;; so far the SIMM signals seem broadly similar. Otherwise, I’m starting to wonder if a bad IC could cause the chime, so I might consider disassembling the ROM… | |
| Posted by: PacificState on 2022-04-27 08:33:41 And… it’s alive! I ended up socketing the chips, and swapping in the VIAs got it going. Thanks again to Bolle for doing this - and also for revising the board so that the latest rev has the right footprints. | |
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