The 78xxx series needs roughly 2.4+V input to output differentinal
to truly maintain regulation with any kind of load on it.
The 2940 series only needs 1.2-1.4V and will regulate to within 20mV
where the 78xxx series is only spec'ed at 200mV or so.
So the 78xx series at even 12.5V in is not guaranteed to stay in regulation.
The voltage will fall below the 10V mark (rather quickly)
the 2940 will stay at 10V even at 11.2V . And that's even with a
full 1 amp output (gauges will pull maybe 1/2 amp worst case)
Both are t he sam package, same pin out etc etc.
The 78xxx should work, just not a stable as the newer 2940 series
that replaced it for 'micro-power' applications.
Paul Tegler
ptegler@cablespeed.com
www.teglerizer.com
----- Original Message -----
From: "James Carruthers" <j.carruthers@rave.ac.uk>
To: <ptegler@cablespeed.com>
Cc: "Martin Pearce" <dungey@pearcem95.freeserve.co.uk>; "spitfires list"
<spitfires@autox.team.net>
Sent: Thursday, August 12, 2004 9:24 AM
Subject: Re: Voltage Stablizer
> Paul,
>
>
> The one's I've found are L78S10's - and theyre in the TO-220 package...
>
> I am about to go outside and fish out an old blown up regulator and put
> one together... and then send it to Martin :o)
>
>
>
> James
>
>
>
> ptegler@cablespeed.com wrote:
>
> >James (and everyone)
> >At least here i nthe states.... the cheapest around is the
> >LM2940T-10.0 low drop regulator. 10 volts out @ 1amp
> >and only needs (spec'ed at) 11.4V to stay in regulation.
> >This is the TO-220 package. So heat dissipation should
> >be more than adequate for Triumph gauge apps. This is also
> >small enough to stuff inside your old stabilizer package so it'll
> >look stock. They work great for me.
> >
> >Paul Tegler
> >ptegler@cablespeed.com
> >www.teglerizer.com
> >----- Original Message -----
> >From: "James Carruthers" <j.carruthers@rave.ac.uk>
> >To: "Martin Pearce" <dungey@pearcem95.freeserve.co.uk>
> >Cc: "spitfires list" <spitfires@autox.team.net>
> >Sent: Thursday, August 12, 2004 5:50 AM
> >Subject: Re: Voltage Stablizer
> >
> >
> >
> >
> >>If anybody is interested I have found a source of solid state 10v IC
> >>regulators in the UK - they cost about #1 each - initial testing shows
> >>them to work brilliantly - and they won't go bang so often!
> >>
> >>
> >>
> >>James
> >>
> >>
> >>
> >>
> >>Martin Pearce wrote:
> >>
> >>
> >>
> >>>Bit of a strange one this. I am revisiting the problems I am having in
a
> >>>reading on the fuel guage of my Mk1 Spit. (gave up last year!)
> >>>
> >>>I recently purchase another fuel sender unit to test if its that but I
> >>>
> >>>
> >was
> >
> >
> >>>reading in my 60s workshop manual that the voltage stabiliser should be
> >>>checked first. The input at the B terminal should be 12v (ie from the
> >>>battery) and yes it is. The output terminal T (which runs to the temp
> >>>
> >>>
> >and
> >
> >
> >>>fuel guages) should be 10v. Mine is down at 5v, which is probably the
> >>>issue. Anyway, I have ordered a new one.
> >>>
> >>>My question is that if the stabilizer is only providing a 5v output,
why
> >>>
> >>>
> >am
> >
> >
> >>>I getting correct readings on the temp guage but not fuel as they both
> >>>
> >>>
> >use
> >
> >
> >>>the same feed?
> >>>
> >>>Cheers
> >>>
> >>>Martin
> >>>'63 Spit4
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