RE: Safe to run XY PCB w/ monitor disconnected?

I still don't get that. First of all, undervoltage on those regulators just
causes them to go to minimum voltage drop and they run cold as ice. Second,
if any thermal condition existed, they are protected against that. They are
also protected against shorts. Backfeeding the output is also acceptable
practice.

FORGET ABOUT IT.

By the way, they only cost about $0.25 and are plentiful.

-----Original Message-----
From: owner-vectorlist@synthcom.com
[mailto:owner-vectorlist@synthcom.com]On Behalf Of John Robertson
Sent: Friday, April 20, 2001 12:25 AM
To: vectorlist@synthcom.com
Subject: Re: VECTOR: Safe to run XY PCB w/ monitor disconnected?

Ah, now I understand!

You MUST raise the outputs of the regulators IF you are feeding voltage
AFTER THEM. In other words, the author is not providing the +/-25VDC or so
that the regulators normally get on their inputs, rather he is providing
somewhat lower voltages (+/-12VDC) than the regulators produce (+15,
-15VDC) and this WILL destroy the regulators if they are left in circuit.

Thus, IF you are providing the +12,-12VDC etc. substitute voltages, then
you MUST disconnect the outputs of the regulators.

John :-#)#

At 08:40 PM 4/19/2001, you wrote:
>Ok I Have a question now On the page
>http://www.geocities.com/SiliconValley/Horizon/2253/vectors.html
>It states
> >>The first thing you MUST do is to desolder/clip the outputs (pin 3) of
> the 7815
>(VR3) and >>7915 (VR1) regulators away from the PCB. If you do not, they
>will get
>HOT and be >>destroyed!
> This is just because the page author was feeding the board 12 volts
> rather then
>10, Right? or Am I missing something? Why would anyone really need to do
>all that
>hacking to put a display up on a scope?
>
>-=Mark=-
>
>
>Rod Spade wrote:
>
> > Bret Pehrson wrote:
> > >
> > > Specifically with Atari -- Star Wars and Major Havoc, is it safe to
> run the
> > > PCB with the monitor completely disconnected or can it cause problems?
> > >
> > > I'd like to work on the games using a scope for the output, and
> disconnect
> > > the monitor (at least the power) until I get the boards working
> correctly.
> > >
> > > The reason I ask:
> > >
> > > http://www.geocities.com/SiliconValley/Horizon/2253/vectors.html
> > >
> > > indicates that the regs output needs to be clipped.
> >
> > I think he just did that so he could use an alternate power supply for
> > the board - but I'm certainly not an expert.
>
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Received on Fri Apr 20 10:50:39 2001