Re: Baked Apple Drives?

[Marsha <menacechgo@aol.com>]

[posted and mailed]

twohandsfree@hotmail.com (John) wrote in 
e639cb5b.0303240942.2cc28a9e@posting.google.com:">news:e639cb5b.0303240942.2cc28a9e@posting.google.com:

>   After a motherboard swap I fired it up, heard a tiny tiny pop,
> smelled smoke and got no disk activity.

Was the pop and smoke from the disk drive? (Hopefully)

If so you probably need one or more of the following ICs 
(in the order I think I remember they usually blew)
74LS125     	    	  Jameco price  $0.39
CA3146 / LM3146
ULN2003A                             $0.39 
MC3470

The two linear chips CA3146 and MC3470 would be the most difficult to track 
down and replace.

see also
http://ground.ecn.uiowa.edu/apple2/MiscInfo/Drives/diskii.ls125


also from an old post by Tony Duell
> A 3740 is a well-known read amplifier, etc, for floppy drives. It was 
> used on a lot of 5.25" units.
> 
> The Apple Disk II and it uses a 3740 
> as the read amplifier. The other obvious chips are a CA3146 transistor 
> array (write driver), a ULN2003 (stepper driver, etc) and a 74LS125 
> (3-state buffer).