H7821 power supply in MicroVAX 3100, SCSI disk enclosures and others

Bill Degnan billdegnan at gmail.com
Fri Jan 31 07:27:09 CST 2020

On Fri, Jan 31, 2020 at 8:24 AM Peter Coghlan via cctalk <
cctalk at classiccmp.org> wrote:

> The recent discussion on BSC protocol prompted me to dig out my Microvax
> 3100
> with DSH32 synchronous serial interface.  It had been idle in storage for
> several years and it wouldn't power up, only giving a brief flash on the
> diagnostic LEDs and a quick twitch of the fans.  There was a slight smell,
> like
> the stale air that comes out of a deflating tyre.
> <snip>

> If anyone has anything with H7821 power supplies in them, I suggest
> checking
> on these capacitors.  If anything with these power supplies is in storage,
> I
> suggest ensuring it is stored the normal way up as this should limit the
> ability of the goo to escape and spread around the power supply.
> And there I was thought I was being safe enough by removing the nicad
> battery
> packs some years ago...
> Regards,
> Peter Coghlan.

Thanks Peter..My 3100 just smoked up the other day, needs repair or a new

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