[Coco] Re: Any problem with connecting 2 floppies to one power supply?

[Gene Heskett]

On Monday 02 February 2004 09:06, Amardeep S Chana wrote:
>"Gene Heskett" <gene.heskett at verizon.net> wrote
>in message news:200402012000.33788.gene.heskett at verizon.net...
>
>> That said, I did it for several years in my grass valley e-disk
>> simulation running on os9, but its duty cycle was quite low. 
>> Never had a problem with it, ever, other than dying wd-1773's in
>> the disk controllers, it used up 3 of them in 13 years.  I think
>> the purple plague ate them, a well known PMOS chip failure
>> mechanism.
>
>Hi Gene,
>
>According to the data sheets, the WD chips were all NMOS even back
> to the 1771 single density parts.
>
>Amardeep

You are probably correct.  Didn't most PMOS parts need a substrate 
bias of -5 to -12 volts?  In which case these didn't need it.  So 
maybe the failure mechanism wasn't the plague, but there did seem to 
be one as I've seen about 5 or 6 blown ones now.  The 3 failures at 
the tv station didn't seem to be static related while hooking up the 
cables that I could see, but one of just sitting there powered up, 
being used maybe 5 or 10 times a day, and the drives would suddenly 
disappear.  At which point I went chasing around to find yet another 
of the short controllers because they were the only ones that would 
fit inside a 19" racks width.  The last time I had to extract a chip 
from a long controller and transplant it.  However, down thru 
history, the lack of a decent line cord, no third pin ground on any 
of that stuff, no doubt did contribute to some failures.  I'm pretty 
sure I blew one here at home from that effect back before I'd put my 
whole system on a single pc power supply.

-- 
Cheers, Gene
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Copyright 2004 by Maurice Eugene Heskett, all rights reserved.