MD2 resistor mod - a different approach?

[Tom Althoff]

I want to be able to switch between my MD2 mic which needs DC applied to the AF line and my Heil Proset Plus headset which doesn't.  

I'm not sure I could fit the resistor that comes with the MD2 inside the female connector at the mic side so I'm looking into connecting pins 6 and 1 together in the female mic connector and putting the resistor in  SERIES with the 5 VDC line going to pin 6 at the male end of the jack.

When the MD2 is plugged in the AF line would get DC applied through the dropping resistor in the 5 volt line.   When I plug in the Proset Plus pin 1 is just audio and no DC applied.

Does anyone see a problem with doing it this way?   I know you won't be able to pull a lot from the 5 volt line after this mod but I don't plan on powering anything else off of the mic connector.    Also...I would not be able to plug my mic into someone else's K2 as it would put the unlimited 5VDC line directly to my mic element.   I practice safe microphoning and never insert my mic into any other K2 except my own so I'm not concerned in either case.

Comments?  Suggestions?

Tom K2TA
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[Don Wilhelm-3]

Tom and all,

There is a solution to using a mic requiring the 5 volts (through a
resistor) and switching to a mic that does not need it which does NOT
require the resistor to be in the mic plug.

Wire the resistor at the mic jack between pins 5 and 6 (pin 5 = FUNC which
is not used), then in the mic plug for the microphone(s) needing the 5
volts, add a jumper from pin 5 to pin 1.  The mic jack will have only AF on
pin 1, and will have +5 volts through the resistor on pin 5.

When wired this way, your Elecraft mic will work on other K2s wired for the
standard Elecraft mic, but another standard Elecraft mic will not work on
your K2.

Additional note - if NONE of your mics have the UP and DOWN buttons
implemented, you can use pins 3 and 4 for any purpose you wish - including
piping the +5 volts on one of these pins instead of pin 5.

73,
Don W3FPR


----- Original Message -----

I want to be able to switch between my MD2 mic which needs DC applied to the
AF line and my Heil Proset Plus headset which doesn't.

I'm not sure I could fit the resistor that comes with the MD2 inside the
female connector at the mic side so I'm looking into connecting pins 6 and 1
together in the female mic connector and putting the resistor in  SERIES
with the 5 VDC line going to pin 6 at the male end of the jack.

When the MD2 is plugged in the AF line would get DC applied through the
dropping resistor in the 5 volt line.   When I plug in the Proset Plus pin 1
is just audio and no DC applied.

Does anyone see a problem with doing it this way?   I know you won't be able
to pull a lot from the 5 volt line after this mod but I don't plan on
powering anything else off of the mic connector.    Also...I would not be
able to plug my mic into someone else's K2 as it would put the unlimited
5VDC line directly to my mic element.   I practice safe microphoning and
never insert my mic into any other K2 except my own so I'm not concerned in
either case.

Comments?  Suggestions?

Tom K2TA
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[Tom Althoff]

That's even better..no cutting of lands on the control board as I would have
had to do.

Thanks once again Don!

And Happy Thankgiving to all on the reflector.

73 de Tom K2TA
K2 #1117-C

----- Original Message -----
From: "W3FPR - Don Wilhelm" <[hidden email]>
To: "Tom Althoff" <[hidden email]>; "Elecraft"
<[hidden email]>
Sent: Tuesday, November 23, 2004 9:17 PM
Subject: Re: [Elecraft] MD2 resistor mod - a different approach?


> Tom and all,
>
> There is a solution to using a mic requiring the 5 volts (through a
> resistor) and switching to a mic that does not need it which does NOT
> require the resistor to be in the mic plug.
>
> Wire the resistor at the mic jack between pins 5 and 6 (pin 5 = FUNC which
> is not used), then in the mic plug for the microphone(s) needing the 5
> volts, add a jumper from pin 5 to pin 1.  The mic jack will have only AF
on
> pin 1, and will have +5 volts through the resistor on pin 5.
>
> When wired this way, your Elecraft mic will work on other K2s wired for
the

> standard Elecraft mic, but another standard Elecraft mic will not work on
> your K2.
>
> Additional note - if NONE of your mics have the UP and DOWN buttons
> implemented, you can use pins 3 and 4 for any purpose you wish - including
> piping the +5 volts on one of these pins instead of pin 5.
>
> 73,
> Don W3FPR
>
>
> ----- Original Message -----
>
> I want to be able to switch between my MD2 mic which needs DC applied to

the
> AF line and my Heil Proset Plus headset which doesn't.
>
> I'm not sure I could fit the resistor that comes with the MD2 inside the
> female connector at the mic side so I'm looking into connecting pins 6 and
1
> together in the female mic connector and putting the resistor in  SERIES
> with the 5 VDC line going to pin 6 at the male end of the jack.
>
> When the MD2 is plugged in the AF line would get DC applied through the
> dropping resistor in the 5 volt line.   When I plug in the Proset Plus pin
1
> is just audio and no DC applied.
>
> Does anyone see a problem with doing it this way?   I know you won't be
able
> to pull a lot from the 5 volt line after this mod but I don't plan on
> powering anything else off of the mic connector.    Also...I would not be
> able to plug my mic into someone else's K2 as it would put the unlimited
> 5VDC line directly to my mic element.   I practice safe microphoning and
> never insert my mic into any other K2 except my own so I'm not concerned
in

> either case.
>
> Comments?  Suggestions?
>
> Tom K2TA
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>
>

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[Don Wilhelm-3]

Walt and all,

Thanks for that info - I should have checked the schematic before I opened
my mouth (well fingers anyway).

The jumper must be removed from the mic header.  Even though FUNC is not
used in the K2, the front panel is wired so that it COULD be used (for some
future something).

This also means that my statement about your mic being able to be used on
another K2 is also incorrect.  -- but everything does work FB if you remove
the configuration jumper.

73,
Don W3FPR

----- Original Message -----

>
> Thanks for sharing this simple, ingenious approach.  I did it this
> morning.
> The only thing I forgot to do the first time was to remove the jumper I
> had
> across FUNC/5, which kept the FUNC circuit tied to Pin 5.  It was obvious
> something was wrong, and I quickly realized I needed to remove that
> jumper.
> Works great now.
>

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[Tom Althoff]

I just finished the mod.   Pins 5 and 6 go to plated through holes that
presented a perfect place to mount the resistor.   I cut the leads of the
resistor first before soldering so that they would not extend through to the
other side of the board.

I now have my new "on-sale" MD2 working and when the adaptor arrives for my
Heil ProPlus! I can just plug it in and talk (hmmm...assuming my voice is
loud enough to not need any messing with the AF gain in the SSB audio path).

Not having built my K2, it was a VERY impressive moment when I pulled the
front panel off after removing only 6 screws.  Wow...pull it off...push it
on...pull it off...push it on...COOL!  No interconnecting cables.   I love
the way this radio was engineered.   Every fits "just right".

Here's a pic of the way I mounted the resistor across pins 5 and 6.
http://www.k2ta.com/resistor.jpg

Thanks again to both Don and Walt for their help!

73 de Tom K2TA
K2 #1117-C

----- Original Message -----
From: "W3FPR - Don Wilhelm" <[hidden email]>
To: "Walter Wilson" <[hidden email]>; "Tom Althoff"
<[hidden email]>; "Elecraft" <[hidden email]>
Sent: Wednesday, November 24, 2004 9:21 AM
Subject: Re: [Elecraft] MD2 resistor mod - a different approach?


> Walt and all,
>
> Thanks for that info - I should have checked the schematic before I opened
> my mouth (well fingers anyway).
>
> The jumper must be removed from the mic header.  Even though FUNC is not
> used in the K2, the front panel is wired so that it COULD be used (for
some
> future something).
>
> This also means that my statement about your mic being able to be used on
> another K2 is also incorrect.  -- but everything does work FB if you
remove

> the configuration jumper.
>
> 73,
> Don W3FPR
>
> ----- Original Message -----
> >
> > Thanks for sharing this simple, ingenious approach.  I did it this
> > morning.
> > The only thing I forgot to do the first time was to remove the jumper I
> > had
> > across FUNC/5, which kept the FUNC circuit tied to Pin 5.  It was

obvious
> > something was wrong, and I quickly realized I needed to remove that
> > jumper.
> > Works great now.
> >
>
>

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[JEAN-FRANCOIS MENARD-3]

Hi Don,

What are you suggest if I must switch often between an MD2 and a
Kenwood hand mic.... It is a little bit hard to remove and add the
jumper each time... Maybe if we can have those jumpers more
accessible.... from dip switches somewhere...


Le 04-11-24, à 09:21, W3FPR - Don Wilhelm a écrit :

> Walt and all,
>
> Thanks for that info - I should have checked the schematic before I
> opened my mouth (well fingers anyway).
>
> The jumper must be removed from the mic header.  Even though FUNC is
> not used in the K2, the front panel is wired so that it COULD be used
> (for some future something).
>
> This also means that my statement about your mic being able to be used
> on another K2 is also incorrect.  -- but everything does work FB if
> you remove the configuration jumper.
>
> 73,
> Don W3FPR
>
> ----- Original Message -----
>>
>> Thanks for sharing this simple, ingenious approach.  I did it this
>> morning.
>> The only thing I forgot to do the first time was to remove the jumper
>> I had
>> across FUNC/5, which kept the FUNC circuit tied to Pin 5.  It was
>> obvious
>> something was wrong, and I quickly realized I needed to remove that
>> jumper.
>> Works great now.
>>
>
>
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>

===========================
Jean-François Ménard / VA2VYZ
[hidden email]

Elecraft K2 #4130

http://homepage.mac.com/jfmenard
===========================

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[Don Wilhelm-3]

Jean-Francois,

Fortunately the Kenwood mic has similar configuration header wiring compared
to the Elecraft, differing only in having 5 volts on pin 5 rather than on
pin 6.  If the Kenwood mic is only used with the K2, you can re-wire the mic
plug to grab the 5 volts on pin 5 instead of pin 6.  OTOH, if you must
retain the Kenwood wiring, proceed as indicated below.

If the Kenwood mic is one of those listed in the Elecraft KSB2 manual, you
would still add the resistor between pins 5 and 6 at the back of the K2 mic
jack and be certain nothing is connected at the mic header to pin 6.  To be
safe, disassemble the Kenwood mic plug and be certain nothing is connected
to pin 6 inside there too - if there is a connection, it should only be used
as a tie-point and can be removed (if there are two wires on pin 6, remove
them from the pin and connect them together) - I think I have covered all
possibilities with that <G>

Then on the mic plug for the MD2, connect pin 6 to pin 1 - the 5 volts
(direct = no resistor) remains on pin 5 to satisfy the Kenwood mic, and will
have the resistor in series at pin 6 for the Elecraft mic requirements.

73,
Don W3FPR

----- Original Message -----

What are you suggest if I must switch often between an MD2 and a
Kenwood hand mic.... It is a little bit hard to remove and add the
jumper each time... Maybe if we can have those jumpers more
accessible.... from dip switches somewhere...



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