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HELP - 512K won't power up
Posted by: 68kPlus on 2022-11-19 18:14:49 Hi, I was just removing C37 (RIFA) from the 512K I recently bought. It was blown, so I de-soldered it and also cleaned up some battery corrosion on the battery contacts. After putting everything back together, I powered it up and nothing. What do I do? Is C37 vital for the Mac to work? Any help is much appreciated.
Posted by: Phipli on 2022-11-19 18:24:16 Take it apart again, and carefully put it back together again as a first step. While you're there inspect your handiwork for solder bridges and trace/pad damage. Its best to remove a part from a working machine when you have a replacement - there wasn't really a need to remove it. Lastly, don't worry and don't do anything in a panic. It will be fine 🙂 it will just take some time to find whats wrong.
Posted by: 68kPlus on 2022-11-19 18:31:37 Take it apart again, and carefully put it back together again as a first step. While you're there inspect your handiwork for solder bridges and trace/pad damage. Its best to remove a part from a working machine when you have a replacement - there wasn't really a need to remove it. Lastly, don't worry and don't do anything in a panic. It will be fine 🙂 it will just take some time to find whats wrong. Thank you for the info. I decided to remove the capacitor as it was blown and I thought it might be safer to remove it and then keep using it. I have taken it apart and put it back together again and nothing. I got shocked too which is weird. I was pulling the plug out and touched something and it shocked me (It hurt). not sure what is going on there. Does the vinyl cover for the AB need to be on for it to work? Thank you for the help.
Posted by: Phipli on 2022-11-19 18:49:11 Thank you for the info. I decided to remove the capacitor as it was blown and I thought it might be safer to remove it and then keep using it. I have taken it apart and put it back together again and nothing. I got shocked too which is weird. I was pulling the plug out and touched something and it shocked me (It hurt). not sure what is going on there. Does the vinyl cover for the AB need to be on for it to work? Thank you for the help. Analogue boards are dangerous and capacitors don't discharge instantly. The cover is there to stop you getting a shock or even killing yourself. Take a step back and think about what you are going to do. What have you touched / unplugged? Have any components got bent over and shorted? Did you put the wrong screw in a hole and it is touching something. What did removing the cap do? I'd recommend comming back to it after a break. Don't touch the uncovered board while its plugged in and give it a chance to discharge before going near it. Analogue boards bite, neckboards bite. Enough to kill. Take your time.
Posted by: Phipli on 2022-11-19 18:50:19 Also, its probably an idea to share some high res photos of the board.
Posted by: 68kPlus on 2022-11-19 18:51:44 Also, its probably an idea to share some high res photos of the board. Ok, I'll do that. Maybe after some time of leaving it there, as I am going to do something else for a while. Are there any measures I can take regarding safety when working on a compact Mac? I don't really know any as I believe a grounding wrist-strap is actually a terrible idea for these older CRT Macs.
Posted by: 68kPlus on 2022-11-19 18:56:06 Question: What if I put the RIFA back in?
Posted by: Phipli on 2022-11-19 18:58:06 Ok, I'll do that. Maybe after some time of leaving it there, as I am going to do something else for a while. Are there any measures I can take regarding safety when working on a compact Mac? I don't really know any as I believe a grounding wrist-strap is actually a terrible idea for these older CRT Macs. I tend to leave things for a day before working on the high voltage and still treat it as charged. I would check large caps are discharged by shorting them carefully, and if possible work with someone in the room that knows you're working on high voltage electronics (safely).
Posted by: 68kPlus on 2022-11-19 18:59:30 I tend to leave things for a day before working on the high voltage and still treat it as charged. I would check large caps are discharged by shorting them carefully, and if possible work with someone in the room that knows you're working on high voltage electronics (safely). That is a good idea. I will continue working on this Mac later. Will you be online in the next several hours? I might need more help. Again thank you very much for the information, it really helps!
Posted by: Phipli on 2022-11-19 19:04:23 Question: What if I put the RIFA back in? The missing cap isn't the issue and I believe it should work without. I'd guess something shorted but that itself may have caused other issues. @cheesestraws, @joshc and others are better qualified for these boards. I've not worked on my Plus' analogue board.
Posted by: Phipli on 2022-11-19 19:05:16 That is a good idea. I will continue working on this Mac later. Will you be online in the next several hours? I might need more help. Again thank you very much for the information, it really helps! Its 3am 🙂 I should be asleep, but will be awake at a more reasonable time later 😉
Posted by: 68kPlus on 2022-11-19 19:05:42 Its 3am 🙂 I should be asleep, but will be awake at a more reasonable time later 😉 Okay. Thank you very much!
Posted by: Phipli on 2022-11-19 19:12:06 What I did put here - was looking at the diagram backwards.
Posted by: 68kPlus on 2022-11-19 19:12:45 Oh wait - it isn't on the mains - its on the rectified side. You need that cap. Its part of what smooths the lumpy full wave rectified supply into DC. You have weird bumpy power atm. OH - so if I put it back (despite it being broken) it should work? I'll buy a new one too.
Posted by: Phipli on 2022-11-19 19:17:08 OH - so if I put it back (despite it being broken) it should work? I'll buy a new one too. No sorry, I was just not paying attention - I assumed the mains was on the right. It isn't. Its also the 120V circuit. But should still inform.
Posted by: 68kPlus on 2022-11-19 19:18:22 No sorry, I was just not paying attention - I assumed the mains was on the right. It isn't. Its also the 120V circuit. But should still inform. So replacing C37 will fix the problem or not? I'm confused 😆
Posted by: Phipli on 2022-11-19 19:19:35 So replacing C37 will fix the problem or not? I'm confused 😆 I don't think replacing C37 will fix it.
Posted by: 68kPlus on 2022-11-19 19:20:12 I don't think replacing C37 will fix it. Oh. Do you have any idea what is going on then? I didn't change anything else, so I don't know what is going on.
Posted by: Phipli on 2022-11-19 19:23:04 I didn't change anything else This isn't likely to be true, you mean "I don't know of anything else I changed". Wait for people used to working on these boards to come online. I just didn't want you to rush in and hurt yourself or worry too much.
Posted by: 68kPlus on 2022-11-19 19:25:19 This isn't likely to be true, you mean "I don't know of anything else I changed". Wait for people used to working on these boards to come online. I just didn't want you to rush in and hurt yourself or worry too much. That's true. I actually called up my parents after being shocked (they weren't happy as they aren't home), and they said I have to find what other safety measures I can take before working on it again. I can understand why they want this as they wouldn't want to find me dead in my bedroom working on an old Mac. I'll wait for others to show up, and see how it goes then. I'm going to start to sound like a broken record, but thank you so much for helping me! I wasn't expecting such a response.
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