UA78MGT4C IC SWITCH 63-269

[Gerald Lemay]

No problems whatsoever. The LM317 is a pretty good garden-variety regulator
good up to 1.5 amp and a voltage differential of up to 40 volts. Notice I
said "differential". In fact the 317 will withstand input voltage several
times that up to the point of insulation breakdown. There is also the 20
watt power dissipation limit to be aware of. The old National Applications
Handbook had a pretty neat high voltage regulator circuit for a couple of
hundred volts as well as another one good for 170 volts DC input! Food for
thought.



-----Original Message-----
From: Heathkit Owners and Collectors List
[mailto:HEATH at LISTSERV.TEMPE.GOV]On Behalf Of Mike Miller
Sent: Tuesday, January 30, 2001 1:53 AM
To: HEATH at LISTSERV.TEMPE.GOV
Subject: Re: UA78MGT4C IC SWITCH 63-269


Hey all-
    I've managed to successfully retrofit an HWA2036-3 with an LM317.  My
supply had two parts wrong with it to begin with.  I first replaced the
417-224, an MPSU05, with an MPSU06, which is very similar.  I then subbed in
an LM317 for the UA78MGT4C regulator, since mine was bad.  I had to do some
pin-swapping of the two regulators, though, which wasn't any great
surprise - pin 1 (317) to pin 3 (UA78), pin 2 to pin 2, pin 3 (317) to pin 1
(UA78)...pin 4 of the UA78 location was left unconnected.  I noticed then
that my output voltage was high...variable, but high.  I reduced the 3900
ohm resistor (R5) to around 2700 ohms +/-.  You'll have to vary the
resistance of the replacement for R5 to get the voltage swing you desire.  I
put in the 2700 and was able to set my voltage right at 13.8.  I left the
supply on for around 20 minutes while watching the voltage on the meter, and
it didn't vary over .1 V or so.  This wasn't under load, but I'd suspect it
should remain fairly constant.  Anyone see any problems with this procedure?
        --Mike Miller, KA9RQW

----- Original Message -----
From: "Michael Tallent" <mtallent at CONCENTRIC.NET>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Friday, January 26, 2001 6:09 PM
Subject: Re: UA78MGT4C IC SWITCH 63-269


> This part is very hard to find, it has not been made in a long time as was
not
> very popular.  It is a Fairchild part, and I have a data sheet that I
could
> scan.  If somebody has a place to put it for downloading it would make it
easier
> for me to only send it one time.
>
> I would think that you could easily sub a LM317.  The 78MG part is a four
> terminal positive voltage regulator with .5 amp max load current.
>
> Mike Tallent W6MXV
>
> JBA wrote:
> >
> > The 442-626 was a 78MGT4C. It was an adjustable voltage regulator (POS).
I'm
> > not positive, but I think it may be obsolete now. I don't think ECG or
NEC
> > has a direct replacement for it anymore. Hopefully someone on the list
can
> > correct me and you'll be able to find one.
> > Good luck!
> > de Benton wb5twc
> >
> > ----- Original Message -----
> > From: "H. G. Jerry Dowell" <RECCOP18 at AOL.COM>
> > To: <HEATH at LISTSERV.TEMPE.GOV>
> > Sent: Friday, January 26, 2001 5:16 PM
> > Subject: UA78MGT4C IC SWITCH 63-269
> >
> > > In process of rebuilding a HWA-2036-3.  Need to acquire or be advised
of a
> > > replacement for the Part # 442-626 ( UA78MGT4C ) IC. Also need a
> > replacement
> > > off on switch for this unit. Part # 63-269. Thank you.
> > >
> > >     Again Soon
> > >
> > > Jerry Dowell
> > > WB0GYR
> > >
> > >
> > > H. G. Jerry Dowell
> > > 19119 / 201 E. Truman Rd.
> > > Independence, Missouri
> > > 64056-2432
> > > RECCOP18 at AOL.COM
> > > WB0GYR
> > >
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