imsai 2

From: jpero_at_cgocable.net <(jpero_at_cgocable.net)>
Date: Tue Aug 17 13:58:29 1999

> Date: Tue, 17 Aug 1999 16:35:15 -0600
> Reply-to: classiccmp_at_u.washington.edu
> From: "Richard Erlacher" <edick_at_idcomm.com>
> To: "Discussion re-collecting of classic computers" <classiccmp_at_u.washington.edu>
> Subject: Re: imsai 2
> X-To: <classiccmp_at_u.washington.edu>

> I'm not sure that "jumpering across" the 7805 will be healthy for the 7805.
> Of course, if the input doesn't drop below the output during shutdown this
> may not be a concern. However, if there's a significant off-board load on
> the input switching supply, and significant capacitance (bypass, for
> example) on the board, it's likely to cause problems.
>
> Dick

Hi,

Actually that is not harmful thing. In fact, nearly all peecees of
any brands and generic of any quality short out the 3.45V regulator
via input and output to get 5V by either a jumper or a low
resistance/high current capable FET in (automatic detection type like
GX4, SP3 and such by Asus for 486). I'm sure that is same story for
the split or single voltage supply modes for Pentium class boards.

One thing about double PSUing from one to another voltages is bit too
much to me from reliablity and cost viewpoints. Feeding 5V and
12V direct to bus is assumed that designer upsize the conductors
enough to keep voltage drops low.

THERE is decent PSUs that can be had in any voltages in multi outputs
from one box and still be switcher. I'm all for switchers for
efficieny and less heat output of quality built.

Most linear regulators are happy on input voltages up to 30V BTW.

Wizard
Received on Tue Aug 17 1999 - 13:58:29 BST