The forward bias mic diode switch was not well covered
in the manual (how to deal with it). I found it after
scratching my head over the distored repeater audio
through the tx-af external input. The resistor was
just a logical choice to forward bias the diode with
enough current.
The reason for the switch (if I can remember) is to
keep the mic from going live during an external line
input ptt... or the converse.
chow for now...
skipp
> "Dennis Adams" <[EMAIL PROTECTED]> wrote:
>
> Thanks for the fast replies!
>
> I will have to see what I can find on that resistor for the mic hi
> connection.
>
> Dennis
>
> --- In Repeater-Builder@yahoogroups.com, "skipp025" <[EMAIL PROTECTED]>
> wrote:
> >
> > Hi Dennis,
> >
> > Everything you need is right on the top row of screw
> > connections (plus a number of things you don't need).
> >
> > I labeled all the connections on the top with a fine
> > point sharpie marker.
> >
> > There is a small 600 ohm (telephone) line driver board
> > option, which most often lives on the chassis where
> > supplied... many people use it for the controller
> > receive audio source [it can supply sub tone filtered
> > (PL, CG or CTCSS) de-emph and gated receiver audio
> > to the external controller] when properly terminated
> > to a resistor.
> >
> > If you don't have the line driver board, you end up
> > using the (terminated) speaker audio or ungated -
> > unfiltered discriminator audio.
> >
> > COS is available on the screw terminals... be carefull
> > as the AC Mains screws are nearby. You should add some
> > type of safe shield or cover over the AC Mains ("mains"
> > makes you think I'm from England/Europe... eh?) unless
> > you're really carefull and trust yourself near exposed
> > ac contacts.
> >
> > TX Audio is a bit tricky, there is a diode switch in
> > the tx audio path that needs a resistor to + positive
> > voltage to turn it on (bias). The answer is just a
> > resistor from the 10 or 12 volt supply to the proper
> > mic-hi terminal connection... it's been more than 5 min
> > so I'd have to go find a Master Pro in the way back...
> > to tell you the exact resistor value & connection I used.
> >
> > If you don't make the mentioned resistor/bias connection,
> > the tx line in audio will sound distorted.
> >
> > A small fan moving light air over the power supply
> > back side will make the filter capacitors much
> > happier as they live near some very hot bleeder
> > resistors.
> >
> > Good luck, enjoy the Master Pro and pray you're not
> > paying the electric bill.
> >
> > cheers,
> > skipp
> >
> > skipp025 at yahoo.com
> > www.radiowrench.com
> >
> > > "Dennis Adams" <[EMAIL PROTECTED]> wrote:
> > >
> > > Greetings,
> > >
> > > I have a GE Mastr Pro Deskmate with the 4EP38A10 Power Supply.
> The
> > > question I have... are the barrier strips at the top the same
> > pinouts
> > > for the TX/RX strips as the 4EP38A12 power supply? I have the
> > 4EP38A12
> > > Schematic.
> > >
> > > I am wanting to hookup a controller and wanted to make sure I have
> > the
> > > COS, audio, PTT, etc correct for wiring.
> > >
> > > Better yet if someone has a schematic for this unit that would
> also
> > > detail the barrier strip designations, please contatct me. I will
> > pay
> > > for a schematic of this power supply.
> > >
> > > Thanks,
> > > Dennis / KB8YGC
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