Mac Classic Analog Board repair help

[yomatiase]

I just bought and Apple Macintosh Classic
When I switched on for the firs time, the fan turn on and the monitor did a glitch and nothing more.
Next day only the fan turned on.

So I did the recap following this instructions. Only changing the 10 caps in the list.

https://recapamac.com.au/wp-content/uploads/2019/08/mac_classic_analog_recap.jpg

When I turned on after the recap, nothing happened, and about 30secs the 470uf 50v popped.
I changed it again, now nothing happens, not even the fan turns on. I just hear a high-pitched buzz for 1 sec and nothing else.

This is the first time I do soldering o electronics repair.
I attached some pictures

The MOSFET looks fine.

I will recheck again if I soldered the caps in wrong places, but lets asume I did it properly.

What could be my next steps?

Thanks everyone!

 

[Garrett]

I hate to break it to you, but it looks like the caps you installed were put in backwards. Check the silk screening on the board, and note the "+" sign. That must be opposite to the (-) you see on the capacitor. If I were you I would replace with new, and not try reusing the ones you have installed. Good luck!

 

[yomatiase]

Oh... jajajajajajajajaa
I didn't check on the polarity. Thanks!!! Hope I did no more harm.

 

[yomatiase]

Should I recap all the caps or only the one marked on the guide?

 

[Garrett]

Some may disagree, but I'd start with just the ones Bruce has marked in the guide. I'm confident you'll get it going again!

 

[yomatiase]

Thank You all! I had progress.
It switches on.
No chime
No image
Fan spins
HD spins too, although sounds dead.

What should I do to get chime and image?

 

[Elemenoh]

Thank You all! I had progress.
It switches on.
No chime
No image
Fan spins
HD spins too, although sounds dead.

What should I do to get chime and image?

Have you recapped the logic board? It's common on this model for the SMD caps near the EGRET (ADB controller) to leak around that chip and prevent soft power from working. If that happened you'll need to recap and clean the heck out of that area. Some times you need to completely remove the EGRET, clean underneath and then put it back in place.

Also, when you say switched on, you mean you flipped the power switch and then pressed the power key on the keyboard, right? This model doesn't turn on with the power switch alone.

 

[Yoda]

Also, when you say switched on, you mean you flipped the power switch and then pressed the power key on the keyboard, right? This model doesn't turn on with the power switch alone.

It doesn't? Both my Classic and Classic II power on/off only from the power switch - I didn't think these models had soft power?

 

[This Does Not Compute]

It doesn't? Both my Classic and Classic II power on/off only from the power switch - I didn't think these models had soft power?

That's correct -- the only compact Mac with soft power is the Color Classic series.

 

[Elemenoh]

Oops I misread the post as color classic. Im a dummy please ignore

 

[yomatiase]

Thanks you all!
I ordered the new tantalium caps, they will arrive in about 3 weeks. I will keep you posted.
Now I will retr0bright the case and keyboard.

 

[Chartreuse]

Looking at the photos I would consider also cleaning the analog board too, getting in there with a toothbrush and Q-tips to remove any remaining electrolyte residue. The stuff is corrosive and potentially conductive so you don't want it spreading further and causing weird issues down the line. I'm only saying this because there looks to still be some residues on the top, especially near the big group of caps. It's not likely to prevent it working now but may cause it to start flaking out in a few months or so.

While I thought I originally cleaned mine enough, I could still smell that fishy smell after powering on until I went back in and really scrubbed it down.

Something else to check that could also cause boot failure is checking the 5v and 12v voltages with a multi-meter when you power it on. After recapping the voltages may still be a little off. I know mine were down at 4.7 and 11.2v after I recapped the board. A tiny tweak to the PP1 pot was able to bright those up to basically dead on. Anything below 4.75v on the 5v rail is asking for weird logic faults as it's below the minimum operating voltage of 74 series logic, and that of the CPUs and such. I personally wouldn't want to see it below 4.85v, especially if there's any ripple on it.

EDIT: Also if you have the parts, the two 1n4148 diodes, DP3 and DP4, near the opto-isolater OP1 are also something that should be changed, especially if you're seeing ripple or a wobbly screen. The opto-isolator OP1 is also a good idea to change if your voltages are low/wobble, it's a CNY17G that is still made new, though I didn't need to replace that in mine. If you are going to replace these after bumping the voltage up with the PP1 pot, then you might want to back down that pot first in case the new components put out a much higher voltage, especially the opto.