MAC SE instability and floppy issues

[Mark Tapley]

At 12:00 -0500 10/7/08, Joe wrote:
>hello all,
>I have an original Mac SE here, which seems to be giving me lots of
>trouble. so far im in a new mobo, CRT (I let the magic gas out of the
>original one, second SE ive done that to!) SCSI and floppy cables, and
>floppy drive. the weirdest thing happens to it, and right now, im
>looking at power supply failure as the next logical guess. my problem
>is, I try to boot up my mac from either internal or external floppy,
>but regardless of which it is, it will read the disk, and on restart
>the floppy disk will be corrupted and will need to be reimaged.
>second, no matter the hard drive I put in it, the mac either will not
>see it, or it will go through, initialize, then at the end a dialog
>box will flash really fast on and off, and the computer I/O will lock
>up while doing this. the other thing that makes me think it is PS
>failure is the fact that one time i hooked the hard drive in to power
>while it was running, and when I did so, the fan speed bogged down
>significantly on spin-up of the drive. is there anyone with pinouts of
>this PS i can use to test it, or any advice as to what failure points
>I should check first? I tried google (they say its our friend...) and
>I get no info as to the voltages of the logic board connector or the
>like. any help is most appreciated!! thanks

On my Plus, I had sporadic problems which ended up being due to the 
connector between the analog (including power supply) and digital 
boards. I took that loose, scrubbed pins lightly with very fine 
sandpaper and isopropanol, sprayed on silicone oil (but I'd recommend 
a contact cleaner instead), and re-seated both ends of the cable. 
Resistance across the cable (measured from solder joint on the back 
side of the analog board to solder joint on the back side of the 
digital board) went down from 10's of Ohms to fractions of an Ohm, 
and the system turned reliable.

The resistance measurement is a pretty easy one to make, with the 
system off. I'd recommend that, at least.
-- 
						- Mark     210-379-4635
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