Elecraft

K-2 5 volts on Mic Jack

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K6IA-Howard Stephenson

K-2 5 volts on Mic Jack

I have a strange one for the group.
I use a TigerTronics SignaLink for PSK. Yesterday I
set the jumpers up to use it on the K-2. The interface
can get it's power from the mic jack. The manual
states that the unit draws 10 ma and I've used it this
way on my IC-735. When I tried power up the
interface(powered through the mic jack) the K-2 would
go to the Elecraft welcome display as if I just
powered up the K-2 then switch back on feq. Is it
possible that the interface has a momentary power draw
that is causing the K-2 to reset for some reason?
Could this cause a problem down line if I tried to
power the interface through the jack?
73
Howard Stephenson K6IA

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Don Wilhelm-3

RE: K-2 5 volts on Mic Jack

Howard,

If your SignalLink interface has large capacitors on its voltage input line,
the answer is YES - it will draw significantly more than 10 ma when you turn
the switch on.

YES it is likely that the SignalLink is causing the +5 volt rail on the
front panel and Control board to drop long enough the cycle the K2 through a
reset condition. The microprocessor directly uses this same voltage, and if
it drops even momentarily, there is the possibility that the K2's 'brain'
can become scrambled.

It is possible that you could leave the SignalLink power switch turned on
and use the K2 power switch to turn everything on and off - but beware that
any electrolytics still will have to charge up at power on and that could
slow the rise time of the 5 volt supply which the K2 microprocessor uses for
a 'power up reset' signalling indication - if you find the K2 begins to do
strange things after the interface is installed, remove it and consider
powering the interface from its own separate power supply.

I would tend to believe that the K2 mic connector power was considered only
for powering such things as microphones and mic pre-amps which draw only
microamps.

RANT ON ----

While it is nice not to have to power each accessory separately, it is
unreasonable to expect that any transceiver will provide power output
capability for any and all accessories that may come along. That is what a
main power supply and power connection devices such as the RigRunner are
for. Each accessory worth its salt should provide for its own internal
power needs - which may be sourced from an adequate 12 volt supply (or
115/230 volt power lines).

RANT OFF ----

73,
Don W3FPR

> -----Original Message-----
>
>
> I have a strange one for the group.
> I use a TigerTronics SignaLink for PSK. Yesterday I
> set the jumpers up to use it on the K-2. The interface
> can get it's power from the mic jack. The manual
> states that the unit draws 10 ma and I've used it this
> way on my IC-735. When I tried power up the
> interface(powered through the mic jack) the K-2 would
> go to the Elecraft welcome display as if I just
> powered up the K-2 then switch back on feq. Is it
> possible that the interface has a momentary power draw
> that is causing the K-2 to reset for some reason?
> Could this cause a problem down line if I tried to
> power the interface through the jack?
> 73
> Howard Stephenson K6IA
>
>

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Jack Brindle

Re: K-2 5 volts on Mic Jack

Don is essentially right as to what is happening, although the MCU is
not being "scrambled." The 5A line is connected directly to the
18C452's reset line (MCLR). When 5A drops below about 4.5 volts for at
least 200 microseconds, it triggers a reset for the microcontroller. It
doesn't take much draw on the 5A line to trigger this condition.

Don and I have extensively discussed the use of the microphone 5 volt
line. I fully agree with his strong suggestion to not use it. In my
case I found problems with RF Feedback that I have been able to
directly associate with my use of the power pin, even though I heavily
bypassed it in my interface box. The symptoms were bad audio reports on
my SSB transmissions on both 20 and 40 meters. Replacing the interface
box with a direct connection (and Mic 5V not connected) solved the
problem.

Like Don, I have moved to power my audio interface box from the main
station +12V supply, and removed the jumper from the MIC header to help
make sure the feedback problems do not return. I agree that it is nice
to have one feed point for power to the peripheral devices, but that
one feed point should not be the K2 - it simply was not designed for
that purpose.

On Mar 18, 2005, at 7:45 AM, W3FPR - Don Wilhelm wrote:

> If your SignalLink interface has large capacitors on its voltage input
> line,
> the answer is YES - it will draw significantly more than 10 ma when
> you turn
> the switch on.
>
> YES it is likely that the SignalLink is causing the +5 volt rail on the
> front panel and Control board to drop long enough the cycle the K2
> through a
> reset condition. The microprocessor directly uses this same voltage,
> and if
> it drops even momentarily, there is the possibility that the K2's
> 'brain'
> can become scrambled.

> I would tend to believe that the K2 mic connector power was considered
> only
> for powering such things as microphones and mic pre-amps which draw
> only
> microamps.

- Jack Brindle, W6FB
------------------------------------------------------------------------
---------------------

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Bill Coleman-2

Re: K-2 5 volts on Mic Jack

On Mar 18, 2005, at 11:46 AM, Jack Brindle wrote:

> Don and I have extensively discussed the use of the microphone 5 volt
> line. I fully agree with his strong suggestion to not use it. In my
> case I found problems with RF Feedback that I have been able to
> directly associate with my use of the power pin, even though I heavily
> bypassed it in my interface box.

I solved this problem.

Instead of +5, I wired a jumper block to a piece of wire, ran it to the
+8 regulator on the RF board, ran the wire up beside the connector and
pushed the jumper wire on the microphone half of the connection. I
already had several accessories wired for a Kenwood TS-430S, which uses
+8 volts as well. Now the accessories work equally well on either
radio.

Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901

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Don Wilhelm-3

RE: K-2 5 volts on Mic Jack

Bill,

While I would not advocate the same solution for everyone, it sounds like
you have a solution that works for you. Do be aware that the +8 volt supply
has its limitations too, and I would not want to venture any guess about how
much current you can draw from it before a problem would be seen.

I will stick to my previous rant that each accessory should include powering
provisions for itself with the input power derived from a stiff, dependable
source such as a +12 volt supply. It is presumptious of a designer or
manufacturer to assume that any transceiver will provide power for any and
all accessories (unless made specifically for a given transceiver where the
accessory powering capabilities are known and have been tested).

73,
Don W3FPR

> -----Original Message-----
>
> I solved this problem.
>
> Instead of +5, I wired a jumper block to a piece of wire, ran it to the
> +8 regulator on the RF board, ran the wire up beside the connector and
> pushed the jumper wire on the microphone half of the connection. I
> already had several accessories wired for a Kenwood TS-430S, which uses
> +8 volts as well. Now the accessories work equally well on either
> radio.
>
>