-
Updated 2023-07-12: Hello, Guest! Welcome back, and be sure to check out this follow-up post about our outage a week or so ago.
Mac Classic Analog Board - Clicking sound with oscillating 12v and less than 1v on the 5v rail
- Thread starter oliviaiacovou
- Start date
My AB was only getting to 9.8v on the 12v rail. After reading a lot, I understood that that was not enough voltage to get everything running. I recapped the board without paying attention to the ESR rating, and got the same results. Then I saw a reference to Amiga of Rochester's list of capacitors that called out low ESR caps, and ordered Panasonic low ESRs (from their FS family). Those solved the issue on the 12v rail and my classic II started right up.
Along the way I also replaced all the components that get listed as "the usual suspects" but that didn't fix anything for me.
oliviaiacovou
Member
Any time I heard clicking from an AB board, it was because of a short somewhere. The power supply was trying to start, failing, and starting again over and over again.
I would never have thought of the electrolytic goop causing the issue. Thanks, I learned somethin'.
oliviaiacovou
Member
Success! I finally figured out what was wrong with my Mac, and I've now recapped it again with smaller caps, now everything works!
Except the hard drive
it seems to have died while I was working on this project, but oh well, I have a PiSCSI board on the way so it won't be an issue for long
So, the issue? Turns out one of the mosfets near the low voltage caps had come loose, which caused the clicking. While I was waiting for my new low ESR caps to arrive I had the Mac running on the old ones and it worked great after it had time to charge up. After I installed the new caps I got clicking again, turns out I had installed a cap the wrong way. No problem I thought, I'll just turn it round and check the others, turns out I missed one, and the next time I powered up the board... a cap started smoking!! Wasn't fun, but it was all okay since I thankfully had loads of spares since I had to buy 10. After I'd replaced that cap, I powered it up and just like that! I hear the bong and get a picture
Thank you to everyone who helped me along the way, glad to finally have a working mac to play around with! Next step is a ram upgrade...
Except the hard drive
it seems to have died while I was working on this project, but oh well, I have a PiSCSI board on the way so it won't be an issue for long So, the issue? Turns out one of the mosfets near the low voltage caps had come loose, which caused the clicking. While I was waiting for my new low ESR caps to arrive I had the Mac running on the old ones and it worked great after it had time to charge up. After I installed the new caps I got clicking again, turns out I had installed a cap the wrong way. No problem I thought, I'll just turn it round and check the others, turns out I missed one, and the next time I powered up the board... a cap started smoking!! Wasn't fun, but it was all okay since I thankfully had loads of spares since I had to buy 10. After I'd replaced that cap, I powered it up and just like that! I hear the bong and get a picture
Thank you to everyone who helped me along the way, glad to finally have a working mac to play around with! Next step is a ram upgrade...
svenvendetta
Member
I suspect the ESR caps may have been a factor ins solving oliviaiacovou's issue in addition to replacing the "usual suspects" list. Reason I think so is I had my AB board recapped by Amiga or Rochester personally and I assume he used the low ESR ones. I've had a few successful starts but still get the clicking noise 98% of the time. I'm going to start going down the list and see what if I have any luck. Thanks for sharing the outcomes here, great knowledge sharing that should be helpful to others.
Success! I finally figured out what was wrong with my Mac, and I've now recapped it again with smaller caps, now everything works!
Except the hard drive
So, the issue? Turns out one of the mosfets near the low voltage caps had come loose, which caused the clicking. While I was waiting for my new low ESR caps to arrive I had the Mac running on the old
Awesome news! Congratulations on getting it restored and, when they arrive you'll have new caps to restore another one (or am I the only sadist who looks to use up all the parts sitting around?).
oliviaiacovou
Member
cheesestraws
Well-known member
The trick is to keep an eye on sales that are local pickup only - even if one doesn't drive (I don't), a lot of people with those auctions are willing to meet one at a railway station - and those auctions go much cheaper.
oliviaiacovou
Member
very true. i also don't drive, although i do get around a lot on my e-bike! unfortunately train tickets to get to london (the place where most listings are) are just too much to justify it. if i lived in the south it would be great, as i can see many macs in and around london which are listed for pretty decent prices
mg.man
Well-known member
Maybe you'd be interested in ...
Thread 'UK Meetup' https://68kmla.org/bb/index.php?threads/uk-meetup.45032/
Could be someone has a "project" compact they'd be willing to let go for a reasonable sum and bring along?
