A Strange Display Issue Has Arisen With My Classic II

[Paralel]

I've noticed recently that whenever my Classic II accesses its HD the screen wobbles. As soon as the HD access stops the screen stabilizes. I have never seen anything like this before. Anyone know what could be causing this to happen?

This system has had a rough road to recovery. When I got it the only thing it did was display the well know SimasiMac pattern :simasimac: . Closer inspection of the system showed the external floppy and SCSI interfaces were both badly rusted. Once I got the case open (#$%@& recessed Torx screws under the handle!) it was obvious that all the capacitors had expressed their collective contents onto the logic board, which not only connected traces inappropriately but corroded the legs on several ICs in the surrounding area. The PRAM battery was also reading a nice flat 0 on my multimeter. With so much crap on the logic board the only thing I could think to do was run it through the dishwasher (I know this is a somewhat controversial approach). After letting it dry out for a few days, then re-installing the RAM, ROM, and a fresh PRAM battery, I resettled the logic board back into its proper home. To my surprise the system bonged and a Happy Mac appeared, followed by The Chimes of Death and a Sad Mac (although it was nothing serious, it turns out my boot floppy was crap).

Although the dishwasher removed all the electrolytic residue off of the motherboard it didn't appear to remove any of the corrosion from the legs of the ICs. Is this corrosion the most likely source of this strange phenomenon I am seeing? Is there anyway to safely remove this corrosion without risk to the Mac? Could it have something to do with the rusty external ports?

 

[aftermac]

Even though you cleaned up the board and got it to boot, the capacitors on the motherboard are still bad and need to be replaced. Any electrical fluctuations will first show up in the monitor, because that is the most sensitive to interference and the biggest power draw.

 

[Mars478]

This is due to the HD giving off magnetic waves which piss off the CRT. Get an ESD cover for the HD or put an original HD in.

 

[Mac128]

This is due to the HD giving off magnetic waves which piss off the CRT. Get an ESD cover for the HD or put an original HD in.

This is NOT the problem. The CLassic is well engineered to compensate for this remote possibility.

aftermac is correct, you have a huge problem looming which will fry more than a few components when the electronics fail. Star treplacing those bad caps now.

 

[Paralel]

Interesting point about the nature of the HD, it is a non-original HD, it's a 500 MB drive. I originally thought it was an 80 MB when I got it but then I realized it had two hidden partitions on it from someone who tried to run A/UX and after recombining and initializing it as a MacOS partition it was actually 500 MB total.

As far as the caps, I didn't realize the first place trouble will show up is in the display (besides the well known SimasiMac). Are there caps that need to be replaced anywhere else besides the logic board, such as the analog board, or is the logic board the only place with this "leaky" cap problem? If its just the logic board I might give recapping it a shot. I know there's a thread around here somewhere with someone selling the caps needed...