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| 128k just died :( |
Posted by: mloret on 2022-02-15 12:05:25
I was testing a drive on my Mac 128k and it randomly cut out. Now It won't turn on and it's making a strange clicking noise. Can someone tell me what has gone wrong here? I'm pretty sure it's a power issue on the analog board (has been recapped).
M |
Posted by: nickpunt on 2022-02-15 13:04:54
Flyback transformer? |
Posted by: Unknown_K on 2022-02-15 13:16:02
I would say you have a short somewhere. Remove the drive you were testing and see if that was it, look for a dropper screw, broken solder joints, shorted diodes etc. |
Posted by: volvo242gt on 2022-02-15 16:17:49
What @Unknown_K says. Was the drive a manual inject 1.4MB drive, perchance? Tried subsituting the manual inject floppy that's currently in my Centris 650 into my Plus, so I could see if I could get the computer to boot a floppy. Drive draws too much power. No chime, flupping sound from the analog board. Flipped the switch off, unplugged the drive, turned the switch back on. Chime and video. Connected the original drive with its stripped eject gear. Turned it on. Chime, video, then a very angry eject motor. |
Posted by: mloret on 2022-02-15 16:17:58
You don’t think it’s the fly back? |
Posted by: mloret on 2022-02-15 16:19:38
What @Unknown_K says. Was the drive a manual inject 1.4MB drive, perchance? Tried subsituting the manual inject floppy that's currently in my Centris 650 into my Plus, so I could see if I could get the computer to boot a floppy. Drive draws too much power. No chime, flupping sound from the analog board. Flipped the switch off, unplugged the drive, turned the switch back on. Chime and video. Connected the original drive with its stripped eject gear. Turned it on. Chime, video, then a very angry eject motor. I unplugged the drive I was testing and the same. I’ll unplug everything and test. |
Posted by: mloret on 2022-02-15 16:20:25
I would say you have a short somewhere. Remove the drive you were testing and see if that was it, look for a dropper screw, broken solder joints, shorted diodes etc. You don’t think it’s the fly back? |
Posted by: volvo242gt on 2022-02-15 16:23:15
I unplugged the drive I was testing and the same. I’ll unplug everything and test. Hmmm, ok. It's possible that you might've overloaded some circuitry on the analog board and something failed. Usually, if the flyback transformer dies, the computer will still boot, it just won't show anything on the monitor. |
Posted by: mloret on 2022-02-15 16:52:50
Hmmm, ok. It's possible that you might've overloaded some circuitry on the analog board and something failed. Usually, if the flyback transformer dies, the computer will still boot, it just won't show anything on the monitor. Okay would that something be a cap? |
Posted by: Unknown_K on 2022-02-15 17:19:08
Tants fail shorted, aluminum analytics fail open-ish (way out of spec).
A flyback can short out so check it to ground.
Sounds like something is tripping the PS which tries to start up again hence the clicking. Old supplies could have many faults but I figure you overloaded something and it shorted or cracked something while messing inside (happens). |
Posted by: mloret on 2022-02-15 17:26:38
I think the clicking type noise is coming from the display.
EDIT: I take it back. I can't tell where the damn clicking is coming from but the different components don't appear to be getting power. I tried different outlets and power cords. Listen...does this ring a bell to anyone?View attachment IMG_3432.mov |
Posted by: Johnnya101 on 2022-02-15 17:42:53
Did it cut out instantly after turning it on or was it working okay for a little while then started having issues? |
Posted by: mloret on 2022-02-15 17:44:57
Did it cut out instantly after turning it on or was it working okay for a little while then started having issues? It was okay and then cut out and never came back. |
Posted by: techknight on 2022-02-16 04:13:49
It was okay and then cut out and never came back.
Because something went hard short. its going to be one of two things. Either the horizontal output transistor shorted due to the flyback, or, one of the secondary rectifier diodes on the output of the power supply went hard short. |
Posted by: bibilit on 2022-02-16 07:39:38
Optoisolator U3 ? |
Posted by: mloret on 2022-02-16 14:19:50
Because something went hard short. its going to be one of two things. Either the horizontal output transistor shorted due to the flyback, or, one of the secondary rectifier diodes on the output of the power supply went hard short. Im learning how to work on these the hard way.
Because something went hard short. its going to be one of two things. Either the horizontal output transistor shorted due to the flyback, or, one of the secondary rectifier diodes on the output of the power supply went hard short. Do you happen to know the location if these? This is all pretty new to me and I learning the hard way. :/ |
Posted by: mloret on 2022-02-16 14:25:21
Im learning how to work on these the hard way.
Do you happen to know the location if these? This is all pretty new to me and I learning the hard way. :/ And what’s a hard short? |
Posted by: techknight on 2022-02-16 16:12:22
And what’s a hard short?
Might be time to travel down the youtube rabbit hole and watch some videos of others working on/teaching how to troubleshoot electronics, and these things.
But a hard short is basically anything on a power supply rail circuit that has a near 0 resistance to ground when its not supposed to, aka, shorted. short circuit. |
Posted by: mloret on 2022-02-16 18:30:08
Might be time to travel down the youtube rabbit hole and watch some videos of others working on/teaching how to troubleshoot electronics, and these things.
But a hard short is basically anything on a power supply rail circuit that has a near 0 resistance to ground when its not supposed to, aka, shorted. short circuit. Roger that. Most of what I know, albeit limited, I learned in the rabbit hole.🤔 |
Posted by: mloret on 2022-02-18 07:42:50
I just took everything apart to isolate the problem. It's definitely on the analog board. I checked the joints and everything seemed okay. I reflowed a couple that looked shady but still the same thing. With everything disconnected, I plug the analog board in and it still makes that ticking sound. It's difficult to tell where it's coming from, but I think it's transformer labeled T3 (Astec 157-0025-A). If this is where the ticking is coming from, does that mean the transformer needs replacing (caps already done) OR is that a symptom of the short somewhere else on the board? |
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