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Just did a continuity test across the pins and Pin 1 is shorting to Pin 5 and, oh, look at that, Pin 5 is to ground! Thank you so much @techknight, you helped a lot. I've got a replacement CRT on the way (hopefully it doesn't get damaged in transit). Would there be a way to rescue this CRT when...

Yes you read correctly. :) Do you know what pins on the tube neck I could test to double check that it is the tube itself?

I'm not the best at electronics: H-K would be where on the board? I could pull the Classic out of storage and give it a quick test. Hopefully the monitor isn't shorted, and I'm 50% sure that it may not be the problem since on first power up it did actually come to life (would draw one quarter...

Made a new thread as I now have a new error! Yikes, this computer is proving to be a real pain!

Some more info: I've traced the brown cable from the CRT to ground. It looks like it's part of the +12v rail that also supplies pin 1 (yellow) of the motherboard. I've found a grand total of one schematic for the Classic Analogue board (both rev A and B ). Looking at the circuit diagram...

I'm now faced with a new problem trying to repair my Macintosh Classic. In a previous thread I thought I had worked out that DP7 had failed since there was a short over the diode. I removed the diode and tested it completely out of circuit. It's fine and works perfectly. There was still...

Completely stumped. I removed the analogue board from the machine, disconnecting the yoke and anode cap (it wasn't connected to the motherboard with the previous test). The cathode end of where DP7 used to be no longer has continuity to ground. I haven't done anything except... remove the board...

I've just removed DP7 from my Analogue board and tested it completely out of circuit. It works fine! Then I found continuity between the two holes where DP7 used to be. I have a dead short to ground somewhere! The Diode was a complete red herring. :( I took a photo and marked off (in orange)...

Ive already got the caps on mine (Rev B, 240v). You should also clearly mark what voltage your BOM is for, too, since there's technically four: A 120, A 240, B 120 and B 240.

Tested CNY17G-3 and that appears to be working perfectly: for those that don't know, diode test mode across pins one and two, with one being the anode. Then 20kO resistance test across four and five. With TDA4605, all pins (except pin 2, which I believe is by design) have resistance to ground...

48 hours later I've removed the IIci case from it's little UV box and I'm shocked that it's actually working. It's painfully slow, but it's working! The front bezel, which is the section being blasted with UV-A, is much closer in colour to the underside of the case. When compared to the right...

That's fantastic! I'll get that ordered ASAP. Mouser and Digikey want £12,00 postage fees if my order is below £33, so I'll be going on eBay instead. Haha :lol:

My meter has a proper diode test mode according to the Engrish manual. Diode 7 has died. Shows a read out of 040 and the continuity beep sounds. In contrast, Diode 7 on my spare Rev A board reads 335. So I guess I'm buying a new diode! May as well buy a new optoisolator, too, regardless if the...

Brilliant! I'll get on that tomorrow. :)

Anything else I could potentially look at before trying PP1? EDIT: I found a Reddit post with similar super low voltage issues. For him it turns out it was a diode located at DP6. Others suggested he check resistors as well before he found the bad diode. I dug out the Engrish manual to my cheap...

Thank you! I'll head to my parent's place tomorrow and steal my dad's electricians screwdrivers to do the adjustment. All of mine are metal AND magnetic so that's a bit too unsafe for my liking. :D

Have a link?

Found some wire and measured from the floppy port. Stable voltage (from what I can tell as it was hard to get good purchase on the wires) The 5v was only outputting about 4v. The 12v was slightly under 10v. Massively under-voltage. I hope the freak-out when I first plugged it in was just a...

P.S. the Retro Recipes video on the topic wasn't just him doing his own thing. He had help of two lads much smarter then pretty much anyone here. Haha!

I'm certainly seeing some kind of result, but it's been under for 24 hours by this point and it did take an initial dip in some very weak peroxide to start with. If I don't see a noticeable improvement by tomorrow afternoon, bringing it up to 48hr, then I'm buying some more peroxide to finish...