68kMLA Classic Interface
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| Classic II constantly reboots/chimes | |
| Posted by: solidpro on 2023-09-26 11:42:44 I took a video - here - can anyone diagnose why? I've recapped both the analogue board or logic board. Anyone know what would cause it to do this? cheers | |
Posted by: Nixontheknight on 2023-09-26 14:44:18I took a video - here - can anyone diagnose why?every time it reboots, it sounds like the power supply is rebooting due to overcurrent, did you replace all the capacitors on the analog board or just some of them? | |
| Posted by: 3lectr1cPPC on 2023-09-26 16:50:00 There's an octocoupler and a couple of resistors I believe that fail on the Classic series analog boards. I forget exactly which ones, someone else can point that out. That may be a good place to start though. | |
| Posted by: joshc on 2023-09-26 21:23:45 A heap of components can fail on the analog board - sometimes just a recap isn't enough. Also PP1 (?) can be adjusted to adjust the voltage output by the analog board. Best to check voltages first and see if they're stable or not, my guess is not based on the behaviour of the machine. | |
| Posted by: bibilit on 2023-09-26 22:22:57 Probably the 5 volt line too low. Replace both diodes Dp3 and DP4… always a weak point. | |
| Posted by: kupouzar on 2023-09-27 04:07:24 Take a look at this thread. Looks like a low voltage issue. I believe the analog board in the Classic II is similar (if not the exact same) as in the original Classic. Edit: of course I meant the analog board, sorry | |
Posted by: Phipli on 2023-09-27 04:17:35Take a look at this thread. Looks like a low voltage issue. I believe the logic board in the Classic II is similar (if not the exact same) as in the original Classic.Hum, they should be pretty different. The Classic is a cost reduced SE. The Classic II is based on the LC family. | |
Posted by: joshc on 2023-09-27 04:44:11Hum, they should be pretty different. The Classic is a cost reduced SE. The Classic II is based on the LC family.I think they must've meant analog board. | |
Posted by: kupouzar on 2023-09-27 04:45:05Hum, they should be pretty different. The Classic is a cost reduced SE. The Classic II is based on the LC family.I meant the analog board. Sorry, my fault. | |
Posted by: Phipli on 2023-09-27 05:15:33I meant the analog board. Sorry, my fault.Ah, that makes more sense 🙂 I've never worked on a Classic II, but I assume the Analog board is the same 🙂 | |
| Posted by: 3lectr1cPPC on 2023-09-27 05:20:35 I believe there were two revisions of the Classic AB, and the II could come with either revision. I think. | |
Posted by: joshc on 2023-09-27 05:27:35I believe there were two revisions of the Classic AB, and the II could come with either revision. I think.Yes, very minor differences though. | |
| Posted by: VeryVon on 2023-09-27 08:12:37 Looking at the construction of the Classic II vs say, an SE you can clearly see the cost-cutting measures. Not a fan of this. The Classic II (a.k.a. "Performa 200") was produced from approx 91-93. Steve Jobs was absent from apple from 85-97. Things that make you go "hmmm" ... p.s. I've slaved over a Classic II, replacing and repairing many things, and it's still a bit flakey. I think the SE and Classic are a bit more robust. I really want to try my hand at booting an original Classic (not Classic II) from ROM some time, but haven't come across one for the right price. | |
| Posted by: solidpro on 2023-09-28 04:27:59 Sorry for slow reply. I had written a post-it note on the front saying I needed to start checking Diodes. Basically I went to sell this on as faulty and then decided I needed to wait until I had the time to do one more pass before giving up. Does anyone know a source of other common failures on the board? I am pretty savvy at doing all the capacitors on both boards but I don't have the knowledge to know exactly what diodes etc to buy to replace them. I do know enough how to measure the voltages simply using one of the connectors on the back - maybe the FDD port you can do it? It's all about summoning up the enthusiasm as well as accepting the fact you can spend a whole day on these things and get exactly nowhere, or you might even fix it and when you take it back off the shelf it's gone bad again.... | |
Posted by: joshc on 2023-09-28 04:34:58 | |
| Posted by: VeryVon on 2023-09-28 05:30:00 Mentions of failing parts / issues here. YMMV. Macintosh classic analog board fluctuating voltageshey, this is my first post to the forum. A couple of days ago I bought a lot of old computers in which came 4 Macintosh classics, not a single one turned on. I chose to start working in one of the 220v models as it is the voltage that my country has. After researching a bit on reddit, this...
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| Posted by: jsilcox on 2023-10-03 12:41:51 Had this same problem. I replace all the capacitors, the two diodes and a couple power transistors on the analog board, but the optocoupler was the biggest culprit. Once I replace the optocoupler it booted, but still reboots randomly after anywhere from 1 to 5 minutes. I am going to check all the resistors, since those are reported as drifting over time. | |
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