PhilCs blog / the latest things hes broken(fixed)

[PhilC]

:lol:

I’ve ordered some caps and will try the other board in a few days.

[PhilC]

So I've managed to fix the flyback on the Mac Classic. The issue was that the screws needed tightening on the base of it, so now the main noise is the dodgy hard drive bearings.

Now I have a slightly different fault in that the 5V is cutting out every few seconds and causing the Mac to reboot. I'm going to have a check of some of the other caps that I'd not replaced as I'd mainly changed the 10 that's specified on another site and its quite possible something else is out of spec.

The voltages do check out okay, around 11.8V and 4.8V respectively.

[PhilC]

I found a couple of caps that were low compared to their rated capacity, so they were changed, ie 700uf compared to 1000uf and then found a burnt diode hiding at the bottom of the board.

So far it's not perfect but it is reseting far less than it was.It doesn't help that the supposed schematics for this analog board don't match the board when it comes to 5V stuff. I've got to find SCR Q8 apparently but that doesn't exist on this board.

[PhilC]

But then thinking some more. It's not impossible that the logic board is causing the resetting. As the logic board had to be repaired but the only test bed I have is the Max Classic that I've had to repair the analog board on

And these classic macs are a pain to work on.

[stephen_usher]

The analogue board is, certainly.

At least with the SE/30 you can use a cut-down ATX extension lead to extend the power/video cable so that you can work on the motherboard safely and conveniently.

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[PhilC]

Thanks @stephen_usher for the suggestion. I'll see if I can get one at some point

Going to park the Max for a bit and continue another project.

[rubber_jonnie]

But then thinking some more. It's not impossible that the logic board is causing the resetting. As the logic board had to be repaired but the only test bed I have is the Max Classic that I've had to repair the analog board on

And these classic macs are a pain to work on.

The resetting is almost certainly the PSU section of the Analog board not starting properly and the voltages being low, I had the same with my Classic, and even after I got it working it started doing it again.

From what I can tell it's not unusual after the PSU section caps have been replaced due to leakage, that the electrolyte that soaked into the board can become problematic later.

With mine I found the problem was that both 5v & 12v were low and the 5v just wasn't enough to get the machine to start properly, and if left long enough it would eventually get going.

By monitoring the 5v line I could see after each start the voltage would increase slowly up to the point where the machine would boot and continue to run. I replaced a lot of stuff in it, you may want to have a look at my old thread.

As for the squeaky hard drive, I'd simply just suggest dropping in a BlueSCSI, not only will it reduce the load on the PSU, it'll run silently. That's what I did and it runs just fine, plus you can have multiple images on there is you want.

[PhilC]

Thanks for the suggestion Jon, I hadn't thought about continuing to monitor the 5v and 12v after setting them. Will monitor and see

In the meantime I'll probably recap my Mac Plus and use that instead.

[rubber_jonnie]

Thanks for the suggestion Jon, I hadn't thought about continuing to monitor the 5v and 12v after setting them. Will monitor and see

In the meantime I'll probably recap my Mac Plus and use that instead.

TBH I found that it could take up to 10 minutes to start properly, and Adrian Black recently mentioned that in his experience the cap juice on the analog board can come and get you later, IIRC he suggested flushing thoroughly with IPA.

[PhilC]

Finally found a use for those unused Apple II floppy drives.

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