The internal preamp is still protected when cutting the jumper.
There’s a 3 step sequenced process built onto the internal TR board. The two
that switch the internal preamp out are still in effect after cutting the
jumper and then using the external PTT.
At least that’s what I interpret from the schematic.
Joe - KC2TN
> On Dec 16, 2019, at 7:04 AM, nosigma@aol.com wrote:
>
>
> James
> Thank you for pointing out protection of the internal pre amp. I had not
> thought of that. For my set up I have not found the internal pre amp to be
> helpful so perhaps I should disable it so I cant accidentally turn it on.
> There are instructions for doing this in the TE manual. Of course I could
> just tape the switch in the down position.
>
> 73
> John
> KM4KMU
>
>
>
> On Sunday, December 15, 2019 James Froemke <jim.k0mhc@earthlink.net> wrote:
>
> Don’t blow up the internal pre-amp accidentally. The RF sense protects
> against losing the hardwired PTT.
>
> > On Dec 15, 2019, at 8:49 PM, KC2TN <kc2tn@comcast.net> wrote:
> >
> > I’d be interested in what they tell you regarding the pin 5-6 jumper.
> >
> > I’m looking to disable this as well.
> >
> > Joe - KC2TN
> >
> >> On Dec 15, 2019, at 6:30 PM, John Young via VHFcontesting
> >> <vhfcontesting@contesting.com> wrote:
> >>
> >>
> >> Taking pin 2 to ground turns on the PA with 5 and 6 still internally
> >> connected.
> >>
> >> However with 5 and 6 internally connected the rf sensing is still enabled
> >> which defeats part of the purpose of the sequencer. The amplifier can
> >> turn on if RF gets to it even if the PTT ground to rf amp lead from the
> >> sequencer is not grounded.
> >>
> >> I have had my 991A on 6m buzz my 1.25m amp, same thing happened with the
> >> W4IY Elecraft on 6m in september. If I had been using a hard keyed pre
> >> amp on 1.25m it would have been fried.
> >>
> >> I opened up the amp and there is no obvious sign of the pin 5-6 internal
> >> shorting wire. Maybe you have to cut a trace now?
> >>
> >>
> >> Calling TE Tomorrow.
> >>
> >> 73
> >> John
> >> KM4KMU
> >> On Sunday, December 15, 2019 John Young via VHFcontesting
> >> <nosigma@aol.com> wrote:
> >>
> >> The TE manual gives some simple instruction for hard keying the amplifier
> >> but out an abundance of caution I want to verify my understanding of them
> >> before I start cutting wires and adding relays.
> >>
> >> The DEMI sequencer gives a sequenced PTT ground to enable the amplifier.
> >> The TE instructions are to cut the internal shorting wire between pins 5
> >> & 6 and then connect the PTT ground to pin 2.
> >>
> >> To enable the RF amplifier the TE instructions are: 1) Connect pin 5 & 6
> >> then 2) connect pin 2 to PTT ground.
> >>
> >> My interpretation of these instruction are:
> >> I need to use the PTT ground to close a relay that connects pins 5 & 6 and
> >> then use an output from this relay to close another relay that connects
> >> the PTT ground to pin 2 on the amplifier.
> >>
> >> Is this correct?
> >> Is there a better way?
> >>
> >> 73
> >> John
> >> KM4KMU
> >>
> >>
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>
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> >
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