Joe,
Just got off the phone with TE systems. It was reccomended that I simply cut a
lead on the capacitor that has one lead on the center conductor of the RF
input. This disables RF sensing so the PA will only turn on when pin 2 goes to
ground. The pre amp is at risk if I happen to turn it on. Easiest fix there
is safety wire to lock it down (off) or a strip of duct tape.
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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