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Repair lifted pads on classic 2

Skate323k137

Well-known member
Oooooooof. I guess....

There are a few right ways to remove smd caps and cold twisting is not one of them.

The most common problem is lifting while applying heat. If one pad melts 1st you're almost sure to lift the other a good chunk of the time.

Without hot air my preferred method is to add a small blob of solder to each pad, and gently push the cap -sideways- while alternating heat between the pads. The cap will gently slide to the side and you can clean up your pcb as normal.
 

chiptripper

Well-known member
Oooooooof. I guess....

There are a few right ways to remove smd caps and cold twisting is not one of them.

The most common problem is lifting while applying heat. If one pad melts 1st you're almost sure to lift the other a good chunk of the time.

Without hot air my preferred method is to add a small blob of solder to each pad, and gently push the cap -sideways- while alternating heat between the pads. The cap will gently slide to the side and you can clean up your pcb as normal.
I honestly hated the idea of twist off, I was so, so resistant to trying it.

I tried using the oh-so-careful soldering iron lift technique suggested by Bruce Rayne, but dwell time was causing issues, and still lost the occasional pad / weakened the pad glue. Cut off carefully with snips once… disaster, never tried that again. Hot air works pretty good, but was getting occasional melted plastic pieces in tight spots and exploding cap cans, and I hated fussing with kapton tape.

Wasn’t until I grudgingly tried the “press down while gently twisting the can portion” trick suggested by MrFahrenheit that I found my groove. Literally haven’t caused one bit of damage since over many recapped boards, no lifted pads, traces, nothing.

I can fully understand it’s not SOP and I wouldn’t necessarily try it on anything other than vintage Mac boards, but it works so well for me. :)
 

Torbar

Well-known member
Hey there, nice classic ii:) Hate to bombard your thread! I have a classic 2 i am working. I cant find a place on the negative side of c10 to check for continuity. Any ideas? I tried grounding it on scsi port.

It goes to that via
 

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zachmayer

Member
“Just put them on crooked” totally worked! I got the thing to boot!

It doesn’t boot every time though— sometimes the CRT doesn’t turn on (but I hear the fan and the drive turn on and I think it’s booting). The sound also doesn’t work, but that was true before it recapped it.

So: any advice for the CRT sometimes not powering on? It’s totally black: it doesn’t even turn grey or light up at all.
 

chiptripper

Well-known member
Your analog board will probably want a recap if not done already.

Some vias on your board look dark, should be shiny. Might want to clear old solder out and replace with fresh stuff. Solder + cap or battery goo can sort of crystallize and become resistive and inconsistent.
 

zachmayer

Member
Where can I get a capacitor diagram for the mac classic 2 analog board?

I bought a replacement capacitor kit here, but I'd like to have a reference to use after I pull out all the old ones, so I put the new ones in correctly!

 

Skate323k137

Well-known member
Where can I get a capacitor diagram for the mac classic 2 analog board?

I bought a replacement capacitor kit here, but I'd like to have a reference to use after I pull out all the old ones, so I put the new ones in correctly!

Usually their wiki has locations.

If I don't have a map, I mark every cap I'm going to replace with black marker before I start, and then I replace them one at a time. It's tedious, but I have a good track record with that method :p
 

zachmayer

Member
So it booted once after the recap (yay!). Now though, the screen is totally black. The CRT doesn’t even power up at all: no jailbars, no grey screen, nothing.

I (very carefully) plugged it in with the case open, and my AC voltage detector isn’t picking up any current at all going into the video board or into the CRT (see photos). I do detect power on parts of the analog board, but a lot of it seems dead.

Has anyone else encountered this (no power to CRT)? I assume it means I need to recap the analog board. Are there particular problem capacities on the mac classic 2 that I should try first?
 

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chiptripper

Well-known member
Analog recap is a good bet. Needs to be done anyway so may as well.

I usually recap everything but electrolytic caps that start with “CP” are the likely culprits, especially the cluster near the speaker and one near the flyback. The big high voltage snap-in cap(s) don’t often leak so people sometimes skip those.
 

bibilit

Well-known member
Not sure a 100% but you are looking for DC current here, not AC, but again can be wrong as the FBT is not bad usually, so i don’t test it.
start with capacitors as Claanu says, those are almost bad everytime.
Testing for good voltages is done at the Molex connector, 5 and 12 volts. 12 volt can be low, but the 5 volt should be 4,85/4,95 as a minimum.
 

zachmayer

Member
Quick update here! I took out the analog board and cleaned the whole thing with some rubbing alcohol and a toothbrush. When I reassembled the whole thing, it booted right up! It now consistently boots, which is awesome! I still have no sound, but I'll work on that. I'm really excited to have this machine running now— Thank all of you for the help and advice!

(And yes, I still plan to recap the analog board =D)
 
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