Weird blue wire on Classic II motherboard

[Mike Richardson]

The Classic II I just sold, has bad sound. The internal speaker is inaudible. With external powered speakers, you have to turn them all the way up, and then it is barely audible.

I pulled the board, and discovered it has some kind of blue wire going from a pin of one of the chips, to a little hole in the motherboard.

http://silvernetworks.net/classicii.jpg

In the picture, I have drawn a blue line over the actual wire, in order to help you see it's path more clearly.

It seems to be held down with little globs of glue or something. It looks very professional, but I have no idea what it's for.

Will cutting it fix the sound? What about replacing capacitors - if replacing one cap would help the sound, which one would it be?

 

[Mike Richardson]

I just cleaned around the capacitors using rubbing alcohol (91%).

That made it worse

Now these popping sounds are emitted from external speaker (internal still doesn't work - maybe I forgot to connect it?) and sound is very poor quality.

 

[Mike Richardson]

This really sucks. Now it randomly sad macs.

I am going to try recapping tomorrow. I have never done it before, and there is very little good information out there for a beginner, but my Macs are dying, because of this damn electrolytic goop.

 

[TylerEss]

Just take your time and be careful. It's not too hard to replace the capacitors.

Good luck!

 

[funkytoad]

darn, that sucks

 

[tomlee59]

Don't cut the wire; it's almost certainly a factory-installed jumper. This sort of thing is very common in electronics. The euphemism is "ECO" or "ECN" for "engineering change order/notice." The common term is "fix for a screwup."

So, in the original PC board layout, there was an error (either of omission or commission), and the addition of the wire was needed to correct it. If you look at the board very closely, you may even see where another connection was Mototooled out of existence. It's likely that yours is a first-run board; later ones were probably laid out correctly, and therefore didn't need the fix.

If you open up lots of electronics, you'll see this type of thing fairly often. It's par for the course, given the crushing schedule pressures engineering teams have to work under.

 

[MultiFinder]

Don't worry, that wire is normal. My Classic II with the four ROM chips has the same thing

That sucks to hear about your troubles with it. The Classic II is a really nice, underloved little machine.

 

[Mike Richardson]

I have 5 capacitors replaced.

The sound has improved a little bit, but it is still degraded. I think the 50V caps are filters for the sound and they must be replaced. I will do that tomorrow when I can buy the correct capacitors.

Whoever bought this Classic II is going to be really lucky.

 

[stevep]

I just opened up one of my Cassic II's and found the same blue wire as shown in the photo a few posts up. Dated 1991 and p/n 820-0401-A.