68kMLA Classic Interface
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| Headless trayloader iMac - audio issues - faulty board? | |
| I'm currently running a Rev. A Bondi Blue iMac setup externally with an ATX PSU. It works, but I've had some teething problems with this setup: - No sound output from the headphone jack - System slows to a crawl or hangs at random times; or doesn't boot.  Through trial and error I've found both issues are related to the sound circuitry. In particular, any time I'm having a slowdown or hang, making physical contact with the sound chip gets things unstuck. This is repeatable and verifiable behaviour. To be specific, I am brushing my finger up against the red highlighted pins, not putting any pressure on them at all – therefore introducing a bit of capacitance. I have a hunch it may be specifically pins 62 and 63 (SPKRR and SPKRL repectively) that are the ones that need tickling. I say this because 1/ I have no sound output on the headphone jack and 2/ I'm missing the proper harnesses and speakers that an iMac enclosure would normally have - and maybe the circuitry doesn't like that.  To anyone who's run an iMac headless like this, have you seen this issue? Tagging @LightBulbFun Posted by: croissantking on 2025-12-06 03:07:58 | |
making physical contact with the sound chip gets things unstuck. This is repeatable and verifiable behaviour. Using some kapton tape, I've isolated the pin to #58 RESET (connected to BURG RST5V L). So, it seems like the chip is not coming out of reset properly? Posted by: croissantking on 2025-12-06 06:12:44 | |
| I remember reading an article years ago about an iMac ATX conversion that was hacked into a Mac II enclosure. Do you have similar plans (putting the thing into a pretty and tidy box, basically) or do you intend to leave it bare for testing and experimentation? c Posted by: CC_333 on 2025-12-07 11:18:21 | |
I remember reading an article years ago about an iMac ATX conversion that was hacked into a Mac II enclosure. I’m not sure yet - probably not but it’s a cool idea. Wouldn’t an LC-style case be perfect? Posted by: croissantking on 2025-12-07 16:11:16 | |
I’m not sure yet - probably not but it’s a cool idea. Wouldn’t an LC-style case be perfect?It would be! When that article was written (not sure when, but probably early-mid 2000s), 3D printing wasn't available, but now it is, so a custom LC-style case could conceivably be created from scratch without sacrificing an existing machine, as the writer of the article did. I don't have the resources to do it, but I'm sure someone around here does. c Posted by: CC_333 on 2025-12-07 16:49:24 | |
I'm currently running a Rev. A Bondi Blue iMac setup externally with an ATX PSU.Whoops, missed the tag somehow, I admit I have not run my headless iMonster for very long (because theres no fan cooling the CPU) but I have put it through quite a few boot cycles n things like that, and its been shockingly reliable, never had much in the way of issues with it all my board and CPU card is a Rev D 333Mhz one but I have never actually tried the Audio output on it, so cant say if that works or not Posted by: LightBulbFun on 2025-12-11 13:44:15 | |
Whoops, missed the tag somehow, Mine is very reliable as well, except for the one issue I described... my board and CPU card is a Rev D 333Mhz one If you wouldn't mind, next time you boot it up, plug some headphones in and see if you can hear anything. Posted by: croissantking on 2025-12-12 06:19:34 |