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cleanycloth

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  1. So I had to leave the project alone for a few days as some family stuff came up. Since then I've spent some time recapping the analogue board with fresh caps from RS just in case any were bad and would fix the wobbly CRT. Unfortunately, we're now back to not starting up again. You can hear the high voltage for the CRT kick in (that little high pitch "fwip" noise) and that's all you get. I checked the voltages and they are now way out of spec to an alarming degree - 5v is now down to about 2.9v and the 12 and -12 are screaming high at 18v and -18v respectively, this is w
  2. tl;dr: Optoisolator was the issue, presuming wobbly screen sides is just bad caps? Hey all! The parts from RS arrived about an hour ago and I popped the machine back together with the new optoisolator. I was too impatient to recap the whole machine (and just in case the new part didn't work, I wanted to rule out one thing at a time) but I turned it on, and... SHE BOOTS! (excuse the camerawork - it was fine on my phone screen until I hit capture, honest!) Blinking question mark floppy icon and all! The only issue I have left is that the pictur
  3. Quick little update - I ordered the 4N35, thanks for the clarification. I managed to get the anode cap off too - I thought you could squeeze the cap and pop it off but you're right - I slipped a screwdriver in there and geeeeently pushed on one side and then lifted it out. I checked over the analogue board and corrosion is minimal. The legs of the power switch (and presumably the internals before I flushed it with contact cleaner) are pretty badly corroded. The ground plane and a few traces have been attacked but they all test absolutely fine, and to make sure I sanded down the con
  4. So after some sanding and measuring of my optoisolator again, it turns out the opto might be faulty. Between pin 6 and 4, my friend's working machine measures 4.5MOhm whereas mine reads about 600Kohm, so it's looking like that's shot (it read as low as 50Kohm at one point). I've been looking around to find a replacement part on here and I've come across two, either the 4N35 or the CNY75GB. The 4N35 is easier to get, is that a good choice? Think I'll pick up some new Y caps for the board as well while I'm at it. Ground seems to be much better now as well, so that's a start. I can't
  5. I didn't even think to check that, and you might be right. The LB is not grounding to the chassis very well due to some substantial metalwork corrosion (and the other side that's clean isn't making great contact either). The ground planes on the AB are corroded from the battery, it seems to be making /some/ contact but it might not be good enough so I've tried to scrape away the corrosion and get better contact. I'll also see if I can get the LB to have better contact too. The AB has been in the machine the whole time until I took it apart last night after the whole incident occurr
  6. I can't seem to edit my last post and I don't like double posting, but here we go: So I gathered up the confidence to take the analogue board mostly out (it's been off all day, I think I managed to discharge the CRT properly - no pops or anything but I definitely touched something under the cap). I've still got the anode cable attached as I'm not sure how to get that off yet. After the fizzing incident nothing on either boards look damaged - no obviously leaking caps, no holes in chips, no burn marks, nada. If I can get the cap off I'll try and take pictures of the boar
  7. Yeah, I thought that was about right since my friend's 512K clicks quickly like mine with the LB out. I'm just hoping I'm not damaging the CRT or anything with it fizzing like that. It's certainly possible that the Rifas are on their way out and it's causing it - one of them is cracked - and I'm using a smart socket (manually!) to turn the machine on and off without having to go anywhere near it with the cover off.
  8. Hi everyone! I decided to have another go at reading the voltages on the board. This time though I fired it up and I could hear a fizzing sound (like gently cooking bacon) that I've not heard from it before so I quickly shut it back down. I took it outside (yes, I'm a wuss haha) and turned it on again. The fizzing was still there and in fact was slightly worse. There are no funny smells coming from the machine. The sound seems to be coming from the analogue board but I'm far too scared to boot it up again in case I damage anything. This was with the logic board conne
  9. Ah yeah, should've said - it's an international version, hello from the UK! This machine is also a bit unusual - it has a 512K front but a 1MB rear shell, board, and it's had a 4MB upgrade in its time. The resistor was already cut. Spotted the opto, mine isn't in a socket and I don't have any spares but I'll keep that in mind. I turned my voltage pot clockwise to match the resistance value of my friend's board (diagnosing things over Twitter DMs is not easy haha) from over 300ohm to about 211. I'll try turning it down further and see what happens. (edit: turned it all the way down,
  10. Hi all! Before I start, I am quite the beginner and I thought this would be an easy fix, turns out it wasn't, so please bear with me I picked up a non-working Macintosh Plus 1MB after a friend send me a link to it - the seller described it as "not powering up" and that was about it. Thinking it would just be a cracked solder joint somewhere I bought it. It's been anything but that, and someone's been in it before me. There's a lot of metalwork corrosion (not caused by the battery it looks like) and some battery corrosion to the switch (which I fixed), power contac
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