[Johnson] 4-prong bias plug for Thunderbolt

[Mahlon Haunschild]

Glenn has the right idea; an alternative approach is to just use the pin 
insert from one of these plugs combined with a metal backshell from one 
of the 91MPM-series plugs.  That's what I've done in the past.

I've thought about making up a small quantity of these connectors 
because I have a good source for the 91MPM-series connectors for use as 
backshell donors; what I don't have is a  matching source for the 
Amphenol mic plugs for use as pin insert donors, and I'm not about to 
slog through the 2-way radio boneyards at hamfests haggling over the 
price of a pile of Motrac microphones that nobody else wants ("$10 each, 
take it or leave it!") when all I want is the connector.

Some of you may recall that I've offered an alternative to this in the 
past: a plastic plug of the correct pin size/spacing similar to the 
Amphenol mic plug that Glenn spoke of, but with a "lip" around the end 
that the wires go into.  This works as well, though it's not as nice as 
the "real thing", whatever that was.  And I do have some available. 

So, repeating my earlier offer:

"I have a small quantity of Amphenol plastic male connectors that fit 
the bias control socket on the back of the Thunderbolt.  These are not 
identical to the original connectors (those had some sort of metal 
backshell) but they match the pin pattern and do work.  $5 for one, $6 
for two, limit two (buy two and make up a test cable with a toggle 
switch, as I did).  The $5 includes Priority Mail shipping."

Note that I netted exactly three connector sales from my earlier posting 
of this ad, so I'm sure you can understand why I'm not exactly diving 
into the Thunderbolt bias plug business.

Maybe I should elaborate on that test cable a bit:  it's just a SPDT 
switch wired up to the three pins on the connector that control the 
bias, simulating switching between operating and standby.  Very useful 
if you are testing or repairing a T-bolt.

Mr Victor:  Please consider this as my reply to your private e-mail to 
me.  Sorry I couldn't reply sooner; it's been a busy week.

regards,

Mahlon - K4OQ

> <>
> ------------------------------
>
> Message: 3
> Date: Sat, 11 Feb 2006 16:55:23 -0800 (PST)
> From: Glen Zook <gzook at yahoo.com>
> Subject: Re: [Johnson] 4-prong bias plug for Thunderbolt
> To: Stephen Victor <victorsj at yahoo.com>, johnson at mailman.qth.net
> Message-ID: <20060212005523.43683.qmail at web52909.mail.yahoo.com>
> Content-Type: text/plain; charset=iso-8859-1
>
> The pin layout on the old Motorola and General
> Electric two-way radio microphones are the same pin
> spacing. However, the insulator around the pins is
> usually too large in diameter to fit inside the metal
> ring on the Thunderbolt jack.
>
> I have taken the insert and VERY carefully turned them
> down using a grinding wheel. It is a pain in the
> posterior to do this but when nothing else is readily
> available one does what one has to do.
>
> Glen, K9STH
>
> --- Stephen Victor <victorsj at yahoo.com> wrote:
>
> Does anyone know how I can obtain a plug that fits the
> bias socket on the back of the Thunderbolt? I thought
> I had one but the prongs are too wide.
>
>
>
>
>
>
>
>
>
> Glen, K9STH
>
> Web sites
>
> http://home.comcast.net/~k9sth
> http://home.comcast.net/~zcomco