Tag: Astatic

Astatic D-104 microphone

I’ve always liked the aesthetic of the D-104 microphones, so when I came across someone selling a couple of them at the local flea market a few months ago, I bought one of them.

  • Astatic D-104 microphone
    Astatic D-104 microphone
  • Astatic D-104 microphone
    Astatic D-104 microphone
Astatic D-104 microphone

None of my radios uses a 4-pin microphone connector, so I haven’t tried the D-104 out yet. I’ll need to make an adapter for it first.

In the meantime, time to take a look inside. I’ve read online that there are a number of modifications that can be made to the D-104, so I wanted to see what the state of this one was.

Undoing three screws allows the bottom base plate to be removed, revealing a terminal strip, the amplifier board, a volume potentiometer, and a battery. The battery was pretty dead (~4V on the DMM) but fortunately it hadn’t leaked.

  • Astatic D-104 microphone circuitry
    Astatic D-104 microphone circuitry
  • Astatic D-104 microphone circuitry
    Astatic D-104 microphone circuitry
  • Astatic D-104 microphone circuitry
    Astatic D-104 microphone circuitry
  • Astatic D-104 microphone circuitry
    Astatic D-104 microphone circuitry
Astatic D-104 circuitry in the base

I don’t know what the innards of a D-104 are supposed to look like, but this seemed pretty stock to me.

The back plate of the microphone head was removed by undoing 4 screws. The microphone element takes up most of the space inside the head. Foam attached to the back plate helps keep the microphone element in place. The foam here was pretty badly deteriorated.

  • Astatic D-104 microphone element
    Astatic D-104 microphone element
  • Astatic D-104 microphone element
    Astatic D-104 microphone element
Inside the head of the D-104 microphone.

The connections on the microphone element look pretty messy because of the rotted foam, so I might need to replace it.

A connection diagram is conveniently attached to the base plate.

Astatic D-104 schematic
Astatic D-104 schematic

I think this will be a fun microphone to use with the radio once I get a proper connection made up (and maybe a new microphone element).

Pondering microphone connection options

Starting to ponder ways to connect the desk mic (an Astatic 877L) we picked up last month to the radio. Right now the mic has an XLR female connector on the end, while the radio uses an RJ-45 modular connector for the microphone input. I figure I have a few options:

  • Replace the existing cord on the microphone with some Cat5 that already has an RJ-45 connector on one end.
  • Make a pig tail with an XLR male connector and some Cat5 with an RJ-45 connector
  • Cut the XLR connector off and splice on a length of Cat5 with an RJ-45 connector

Fortunately, the bottom of the microphone has this handy wiring label. There aren’t very many wires to connect up to the radio.

Astatic 877L wiring diagram
Astatic 877L wiring diagram

Having a look inside the base of the microphone, everything looks to be wired up as shown on the label. It looks like if I choose to replace the cable with a length of Cat5, it will be a little bit of work, but shouldn’t be too bad.

Wiring inside the microphone base
Wiring inside the microphone base

From the Kenwood TS-480 manual, the pin-out for the microphone connector is

  • 1 – UP
  • 2 – +8V
  • 3 – GND
  • 4 – PTT
  • 5 – MIC GND
  • 6 – MIC
  • 7 – N/C
  • 8 – DOWN

Looks like red (XLR pin 2) would go to PTT (4) and black (XLR pin 3) I think would go to MIC GND (5). Not sure where the white wire should be connected to, but it currently goes to pin 1 on the XLR connector. The green wire in the mic doesn’t appear to be connected to anything.

The downside to replacing the mic cable with Cat5 is that the wires are quite a bit thinner, so I”ll have to give extra thought to strain relief at the microphone base.