[TechAssist] Re: good sub 78m05a

  • From: gulftech@xxxxxxxx
  • To: techassist@xxxxxxxxxxxxx
  • Date: Fri, 30 Dec 2005 19:00:14 -0600

You are correct.

I think Phil had too much pre-New Year's spirit.

Right, Phil?


Ken Smith
Gulf Technical Services
3034 Gulf Breeze Parkway
Gulf Breeze, FL  32563
850-934-8324 (Voice) 850-932-0819 (Fax)

On Fri, 30 Dec 2005 14:09:06 -0500 "Christopher Barnak"
<cbarnak@xxxxxxxxxxxxx> writes:
> Phil,
> I use to design custom circuits when I used to work at the 
> GE TV plant in Portsmouth, Va. We were never able to use
> a positive regulator for a negative regulator, we had to use
> the 79xx series regulators for negative voltages.
> 
> 
> Christopher Barnak, CET
> Norfolk Public Schools
> Electronics Maintenance
> 966 Bellmore Ave.
> Norfolk, Va. 23504
> 
> Phone 757 628 3385
> Fax    757 628 3392
> cbarnak@xxxxxxxxxxxxx
> 
> 
> >>> pbader@xxxxxxxxxxxxxxx 12/30/05 11:16 AM >>>
> And that ground leg zener trick opens up a way to make a variable
> regulated 
> DC power supply source.I imagine with a pot in the ground leg,or 
> some
> such 
> arrangement? Now, if you need a negative polarity output from a
> positive 
> output reg IC,just turn the reg upside down.
> ;-)
> Phil
> Philip Bader
> Polk County School Board
> Electronics Shop
> Bartow,Fl.
> (former owner, Jan Phyl TV INc.,
> Winter Haven, Fl. from 1976-2006)
> email: pbader@xxxxxxxxxxxxxxx 
> 
> ----- Original Message ----- 
> From: "Gary McCartney" <gary@xxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Friday, December 30, 2005 11:11 AM
> Subject: [TechAssist] Re: good sub 78m05a
> 
> 
> > Yes, certainly a 78M05 can be subbed with a 7805. 78M05 is rated 
> 0.5
> > amps and a 7805 is rated 1 Amp. There is no reason to even stock 
> the
> > 78M05, just have a few 7805's on hand. Same goes for any other
> regulator
> > in the family- 7812, 7808, etc.
> >
> > Generally speaking, over the years reading these tech emails, I am
> > amazed at the lack of knowlege about these IC's, they are basic
> > fundamental electronic components like a diode or a transistor. 
> Any
> > reasonings?
> >
> > Did you know that you can raise the output voltage of a 78xx 
> series
> > regulator, by inserting a zener diode from the ground pin of the 
> IC
> to
> > ground? If you want an 8V regulator but only have a 5V regulator 
> 7805
> in
> > stock, you can insert a 3V zener from pin 2 of the reg to ground 
> and
> get
> > an 8V reg. (as long as the back plane of the regulator IC is not
> > connected to ground itself because it is common with pin 2, unless
> of
> > course we are talking about a plastic backed IC)
> >
> >
> >
> >
> > Gary McCartney
> >
> > McCartney Electronics
> > Guelph Ontario Canada
> > Est. 1984
> > email: gary (at) number63.ca
> >
> >
> >
> >
> >
> >
> >
> > pete wrote:
> >> can i use a 7805a to sub a 78m05a anyone has done this before? 
> its a
> 5 
> >> volt regulator from a sony power supply model is kv35v35
> >> Perdomo Tv Inc Since 1972
> >> Miami.Fl
> >>
>
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