Breaking a Classic II One Step at a Time (Help!)

[Hurry]

Good afternoon! I purchased a Classic II a few weeks ago. I really enjoy the activity of restoring and future proofing old electronics. I've successfully restored and/or recapped an Amiga 600, a number of Atari and Commodore 8-bit micros, and a slew of video game consoles and handhelds including not one but two Vectrex. I'm not a total newb, but I'm not anything like an expert. I have an IT background but not electrical engineering - my knowledge is spotty. For example, I don't know how read a schematic and the best I can manage with my multimeter (with any confidence) is continuity testing.

With the fear of working around CRTs diminished from working on the Vectrex's, I thought I'd be ready for the challenge of the compact Mac.

When I received the system it powered on and worked immediately (it's the 4/80 model). On second restart, however, I got the messy checkerboard. Cracking the case, I saw that the caps on the logic board had leaked pretty badly sometime in the past. I did a thorough soft brush / IPA bath manually and the system powered up and worked great for days.

I ordered the recap kit for both the analog and logic boards from Console5 and an internal BlueSCIS drive. I also had a 60mm x 25mm Noctua fan from a previous project. All ready to future proof the machine, I started with the fan, which went fine. Next step: analog board recap.

I thought I did a nice clean job - but on first startup - POP - I blew C8. Some genius (I don't know who) managed to reverse the polarity on the thing. Ordered replacement cap and replaced the bad actor an hour ago.

Fingers crossed, I power the Classic II back on and... no pop, but the screen is all moving vertical bars and there's a nasty clicking noise. I powered it off immediately. Waited a few moments, powered back on - this time no display, but the clicking sound persists.

Aside from taking a perfectly good working Classic II into progressing levels of broken... I'm not sure what to do next. I checked all of the rest of the caps for reverses and found none. I've read that clicking is probably something power supply related, but that's pretty broad. I'm skeptical that this is just a dry solder joint, given all the change I introduced.

Any ideas?

 

[Kai Robinson]

Can you take a photo of the screen when you try? Clicking is usually PSU shorting and failing - might be a short to ground somewhere else.

 

[Hurry]

The screen is stone cold blank since that first power up after fixing the reversed cap. I just disassembled and reassembled thoroughly. Same result. I'm trying to "listen around" to see if I can identify a general location where I'm hearing the clicking, but I'm not having much success. I feel nervous about leaving the unit powered on while it clicks, so I'm not sure how long I can leave it on to attempt to identify the location.

 

[Hurry]

You know what I can tell though? The hard drive isn't getting power. The fan does. The clicking isn't perfectly in rhythm, though it is rapid.

Update: Things are progressively worse every time I try and power this on. Now the fan just jitters but doesn't rotate. I'm going to stop turning it on.

 

[Kai Robinson]

Yep, you have a short to ground. With the logic board disconnected, will the chassis power on?

 

[Hurry]

I am having a VERY derpy Christmas over here. I scanned that board THREE times, in different directions, to check that I hadn't reversed any other caps. After all that powering on and off made another start to bulge - CP2. Sure enough, it was reversed as well. In fairness to me (though not much), the silkscreening isn't very clear on that one.

Man, I never post in forums. I draft a lot of drafts, but never hit Submit. Figures the first time in a long time I pull the trigger, I find my own problem.

Thanks again for your help Kai - I still don't know if I would have tracked this down as quickly without trying the steps you suggested.

Of course, the recap didn't restore sound (I didn't mention that before sorry) - but whatever, it's not DEAD anymore!

 

[Kai Robinson]

You're welcome - glad what i said helped!

 

[Hurry]

I hate searching for problems and finding old threads without clear resolution. This issue is solved.

RECAP (no pun intended)

Prior to doing any work on my Mac Classic II, sound did not function.

1. After recapping the analog board I encountered degrading electrical functions. Symptoms included a rapidly flickering checkerboard pattern on the screen that disappeared for good, followed by lack of power to the hard drive and fan. A rapid clicking sound was coming from the analog board.
2. Careful inspection revealed that I had two capacitors (CP2 and CP8) installed backward, polarity reversed.
3. Removing and replacing these capacitors (in my case both suffered visible bulging), the issue was resolved.

I then proceeded to recap the logic board, fixing the sound.

 

[ScutBoy]

The "recap it" answer to most similar issues is only a stereotype because it's often true!

Not slagging on you, @beeblebrox ! I've definitely put a few caps in backwards in my day, and taken a _long_ time to figure it out! The full recap is also just good preventative maintenance for machines of this vintage in general.

 

[svenvendetta]

This is why I (with no shame) have sent my boards for recap out to experts. Well worth the $$ and no hassle to me and there is still plenty I can do (swapped CRT's, SSD config and setup, retrobrite, etc...) to make the restore mine. Very impressed you fixed this!

 

[Hurry]

Thanks! For me, the hassle is why I do it. Aside from times like this, fixing/futureproofing is my favorite part. In fact, as I'm trying to configure System 7.5 for this, I'm coming to realize that I have far greater understanding of the hardware than I do of the operating system or the computer's usage!