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The Macintosh Classic II is a throw back to the original design language of the Macintosh 128. Apple was trying to regain the momentum as Apple was fighting a down turn as there just wasn't enough systems out in the wild yet.

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It won't power on and it looks like something it's shorting out.

Hello, now I have to say that the problem that I have it's with a Macintosh Classic II and not a 30 SE, but unfortunately there is not way of selecting it.

Anyway the problem is that the Mac will turn on and the fan spins but after 30 seconds the fan starts to make some shorting out noises like if something is shorting out but the fan is working, there is nothing plugged in except for the crt which it cannot be unplugged since is part of the power supply board.

Also another problem is the motherboard that won't give any signs of life, now this could be all faults from the bad capacitors that there are on both motherboard and analog board...if you need a link to the video to see what does happen don't hesitate to ask I will give to u a link to YT.

Oh almost forgot there is also something that looks like an amplifier for the speaker that it was covered in oil and some kind of battery acid (no the battery hasn't leaked).

Don’t ask me why there is glue everywhere…the previous owner probably fixed just fine for make it work 1 week so he could have sold it to me… :/

https://youtu.be/LxNNSadprsY

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Have you replaced all of the electrolytic capacitors in this computer?

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@andrewsawesome

Not all of them, because the ones on the motherboard didn’t leaked and they tested good, the ones on the analog board, I’ve been told yes but these nichicon seem stock to me though, also yes before it took a while to power on and it needed some “recharging” although idk because it’s like shorting out and powering, still do you think that shorting out is a common problem with old caps?

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Did you pop in a new PRAM battery? Also can you take a clearer picture of the area you circled (zoom in)

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Yep new PRAM battery but nothing works :/

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@imacpowpcintm - The circled component is a power transistor.

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@imacpowpcintm I know it's a bit late but just wanting to clarify a few things. The circled part is indeed NOT a power transistor. It is a MBR1045 Schottky Diode

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You definitely want to totally recap this board. First off, it is 30 years old and second, you had somebody that used a bunch of goop on it, for whatever reason. As for your caps, you can use the higher voltage ones. Never lower and always keep the proper capacitance. Remember that your power board is also the sweep board. It will have the video circuitry on it as well. Luckily, this was made before the time of blackened out reference designators and Black Helicopter behaviour by a fruity company. All you need, is the schematics that will identify the component and the circuitry. No BV necessary. This Macintosh Classic II Schematics worked for my rebuild. Hope you got it fixed.

Update (02/15/2023)

@imacpowpcintm The capacitors on the logic board are all SMD caps and no through-the-hole caps on that board. @andrewsawesome is right that the SMD caps could, in theory, be removed by snipping their ends off. However, on this board there are some tight spots where it is almost impossible to do so. I used my hot air rework station to remove those. Since there are no other SMD components around, no issues with accidentally desoldering those :-) To order these caps, it is best to also have the outside dimensions. Mouser.com had all the replacements.

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@oldturkey03 - All Classic Mac systems caps are potted like this. I think the reason was to dampen the whine these PSs often had. This is mild from what I encountered when I was fixing them.

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@oldturkey03

Hello, sorry for the late reply, well apparently the guy who previously owned glued the top of the capacitors for avoiding some explosions, also that diode has been cut and then soldered back in place and some hot glue was applied (oh god!). I hope to have some free time this weekend to remove the remaining caps and buying some new ones. Anyway thanks again for your help! And have a nice day. :)

Ps: unfortunately I don't own a hot air gun so I will have to carefully desolder the old caps from the logic board.

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@imacpowpcintm I Figured something like that. The 15 boards that I have just done were pretty much without any goop and so were all the previous ones. Of course, the caps can be removed with a soldering iron. Just use a wide tip and plenty of flux. The only other suggestion I have would be to remove the battery/holder. Replace that with a CR2032 since you won't have to worry about that leaking. Have fun rebuilding it and enjoy your Mac after.

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See if this offers some help The in's and out's of the Mac Classic II

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Actually I already have that pdf but it says “replace motherboard” so…not rly that helpful 😅…anyway I’ve uploaded a new photo and a link to a vid were I show the problem.

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Well its clear the power supply is working! You've go a running fan and the CRT tube cathode is glowing. So your issue is either the analog logic to create the image on the CRT or the logic board. As we don't hear a Bong my money is on the logic board.

Now the real fun begins! Apple never offered the schematics and board views for the logic board. There are some folks who reversed engineered the circuitry. You'll need to buy what they offer and then you'll need to carefully trace out the logic using your DVM. So lets say you locate the bad component many of these components are getting hard to find, the world moved on... In the end it might be just easier finding a logic board.

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@danj

Well from what I can see I’ll better take my hands on a new macintosh because I’ve just removed all the old capacitors from the analog board and…surprise! There it was a lot of green/yellow acid…soo they leaked but recently because it didn’t corroded too much yet.

So…new capacitors (for both boards) probably other 2 new components…so rly at this point I don’t think it’s worth it…I will try with some new caps anyway…

Also the power that came out from the supply wasn’t stable, you can notice it by the fan making weird noises and getting 11-14 volts and nothing is plugged in the board (only fan and crt)…

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@imacpowpcintm I would recommend keeping the board for spares if you want to get another Macintosh Classic II. You can get the surface mount electrolytic capacitors off by cutting them with a side cutter.

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@andrewsawesome Yes well I was thinking to get a color classic but for now I will give it a shot by replacing the capacitors since they are quite cheap and can be done quite easily, if nothing works and I can find another classic II in good condition I will sell it as spare parts and buy something else. Also I was thinking about twisting the caps to remove them but then I think that it's too aggressive so, I will be careful by cutting them of.

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....... さん、ありがとうございました!
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