Got a hold of a gorgeous Robyn T-240D Yellowbird which needs repair on the
receive. I have question regard microphone wiring.

I have an amplified Astatic D-104 with the older T-UG8 stand. The Astatic manual
says to use a .01 cap in line with the white wire, and to use High impedance mic
only, which I assume it is.

The Gemtronics GTX-5000 (which I thought was thew same radio), does not require
it. Am I missing something?

Vinnie S.

On Sep 24, 12:10 pm, Vinnie S. wrote:
I have an amplified Astatic D-104 with the older T-UG8 stand. The Astatic manual
says to use a .01 cap in line with the white wire, and to use High impedance mic
only, which I assume it is.

They may say this for one of two reasons:
They may need DC isolation from mic to radio (should have a series cap
already... so this is not likely) or
They want to reduce low frequencies exiting the mic. This is the most
likely reason.
www.telstar-electronics.com

On Mon, 24 Sep 2007 12:26:30 -0700, Telstar Electronics
wrote:

On Sep 24, 12:10 pm, Vinnie S. wrote:
I have an amplified Astatic D-104 with the older T-UG8 stand. The Astatic manual
says to use a .01 cap in line with the white wire, and to use High impedance mic
only, which I assume it is.

They may say this for one of two reasons:
They may need DC isolation from mic to radio (should have a series cap
already... so this is not likely) or
They want to reduce low frequencies exiting the mic. This is the most
likely reason.


The Gemtronics GTX-5000 is essentially the same radio, yet the guide doesn't
same the same about it.


Vinnie S.

On Mon, 24 Sep 2007 13:10:39 -0400, Vinnie S.
wrote:

|Got a hold of a gorgeous Robyn T-240D Yellowbird which needs repair on the
|receive. I have question regard microphone wiring.
|
|I have an amplified Astatic D-104 with the older T-UG8 stand. The Astatic manual
|says to use a .01 cap in line with the white wire, and to use High impedance mic
|only, which I assume it is.
|
|The Gemtronics GTX-5000 (which I thought was thew same radio), does not require
|it. Am I missing something?
|
|Vinnie S.
|
|------------------

I am not really familiar with either radios. Without seeing the input
circuit my first inclination is to do a DC block and secondly to do
some simple form of impedance matching.

As for the second radio not requireing the cap, that could be due to
the radio not being manufactured at the time the T-UG8 stand was made
so that Astatic did not know of it. Also the mic input maybe a bit
different despite the rest of the radio circuits being identical. A
lot of radios were made to work with dynamic mics and required low
impedance inputs. The D-104 line works well with tube rigs which are
usually high input impedance.

james

On Mon, 24 Sep 2007 19:46:55 -0400, james wrote:

I am not really familiar with either radios. Without seeing the input
circuit my first inclination is to do a DC block and secondly to do
some simple form of impedance matching.

As for the second radio not requireing the cap, that could be due to
the radio not being manufactured at the time the T-UG8 stand was made
so that Astatic did not know of it. Also the mic input maybe a bit
different despite the rest of the radio circuits being identical. A
lot of radios were made to work with dynamic mics and required low
impedance inputs. The D-104 line works well with tube rigs which are
usually high input impedance.

james


I am thinking DC block. One of the pins has hi voltage. I have to see if it
jives with the white wire.

Vinnie S.

On Sep 24, 2:39 pm, Vinnie S. wrote:
The Gemtronics GTX-5000 is essentially the same radio, yet the guide doesn't
same the same about it.

Can't account for that... maybe Gemtronics documentation isn't up to
snuff.
www.telstar-electronics.com

On Tue, 25 Sep 2007 05:31:55 -0700, Telstar Electronics
wrote:

On Sep 24, 2:39 pm, Vinnie S. wrote:
The Gemtronics GTX-5000 is essentially the same radio, yet the guide doesn't
same the same about it.

Can't account for that... maybe Gemtronics documentation isn't up to
snuff.


The General consense from about 3 people, is that it is a DC block. I can verify
it by seeing if the corresponding pin has the 200+ volts I hve been reading
about. The problem was the Gemtronics threw me for a loop.

Vinnie S.