[TechAssist] Re: good sub 78m05a

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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