Astatic Microphones

Schematics & Wiring Diagrams

557 Trucker II & D104M6

TMD-107 Relay
TMD107 Relay

TMD-107-Em D-104M & 555 Trucker - All with electronic switching
TMD 107 Electronic


Electronic / Relay switchng conversions
Hand mic rewiring

Mic rewiring

G Stand

UG8 Stand

T-UG8 Stand
TUG8 Stand


T-UG9 Stand
TUG9 Stand

T-UP9 Stand
TUP9 Stand





TU Kit UG8 Stand

As each operation is performed check it off as "completed".

Unpack the TU-Kit and you will have:

1 Bracket assembly with battery clip and volume control. (Handle volume control with care so as not to scratch the carbon track.)
1 Amplifier assembly
1 Battery
1 Battery connector
1 Red jumper lead
1 Screw
1 Set of instructions

1. Remove microphone from stand - set aside in safe place.

2. Remove bottom plate by removing three screws in base. Save the bottom plate and screws.

3. Cut out and discard the GREEN jumper lead from terminal 3 to terminal 8. (See diagram for terminal numbers. (Fig. 2)

4. Cut out and discard the bare jumper wire between terminals 1 and 4.

5. Remove the cable clamp and cable clamp screws.

6. Locate the bracket assembly on the cable clamp boss under the table wires (Fig. 1). See the illustration for location. Replace the cable, cable spring and cable clamp. Secure the assembly on cable spring side with screw supplied. Secure other side of cable clamp with one of the screws previously removed.

7. Remove the terminal strip screws.

8. Locate the amplifier board (component side toward base) under terminal strip lugs as illustrated. Replace the terminal strip screws and tighten. (Fig. 1)

9. Terminal 3 - Solder GREEN amplifier lead.

10. Terminal 2 - Solder BROWN amplifier lead.

11. Terminal 4 -

(a) Unsolder WHITE/RED and WHITE/GREEN - push aside.
(b) Solder to terminal 4:
1. VIOLET amplifier lead
2. One end of RED jumper lead supplied
3. RED battery connector lead

12. Solder other end of RED jumper lead to volume control terminal as illustrated. (Fig. 2)

13. Solder BLUE and ORANGE amplifier leads to volume control terminals as illustrated. (Fig. 2)

14. Terminal 7 -
1. Unsolder the BLACK cable lead - push aside.
2. Solder the BLACK battery connector lead.

15. Terminal 1 -
1. Solder the WHITE/GREEN lead of step 11.
2. Solder the BLACK cable lead of step 14.

16. Terminal 8 -
Solder the WHITE amplifier lead.

17. Decide whether "Electronic" or "Relay" type operation is desired. This determines where WHITE/RED lead of step 11 is attached.
For "Electronic" operation solder WHITE/RED to terminal 1.
For "Relay" operation solder WHITE/RED to terminal 6.

18. Snap the battery connector on battery and push the battery into battery clip.

19. Align the bottom plate template on the felt side of bottom plate with screw holes as marked. Locate and drill the 1/2 inch diameter hole through the plate, (Fig. 3), if it is not already drilled as supplied by the factory.

20. Position the bottom plate with drilled hole over volume control shaft and secure with screws previously removed.

21. Turn volume control (with screw driver) counter clockwise to zero. Replace microphone on UG-8 stand. Plug cable into transmitter.

22. Activate the transmitter by means of the actuating bar. Adjust volume control with a screw driver to desired modulation level.

23. DO NOT EXCEED 100% MODULATION LEVEL. In addition to inviting a FCC violation notice there is a very real possibility of damage to the audio stages of the transmitter due to excessive audio. In the event it is difficult to adjust the volume control low enough, it is suggested a 470 ohm 1/4 watt resistor be soldered from WHITE cable lead to ground. at either end of the cable. (Terminal 8 to terminal 1 in the UG-8 stand base). Generally, once adjusted the volume control will not need resetting during equivalent operating conditions. The full modulation level capability of the amplifier will seldom be required, except under unusual conditions. If you find it necessary to use most of the amplifier gain, you should check to be certain the gain is really needed.

24. Caution must be used on sets on which the outer housing is not both DC and RF ground. Touching a metal microphone case to the housing may result in damage to the set. In isolated cases RF pickup may cause improper performance. In case of this type of trouble, please get in touch with the factory for instruction.

Special Instruction Notes

1. The combination of these amplifiers with high level microphones may result in critical gain setting. A "L" pad comprising two resistors results in much less critical adjustment.

L pad

Insert 4700 ohms in series with the WHITE cable lead. Shunt 470 ohms from WHITE cable lead to ground.

2. When wiring microphone cables and plugs to equipment, the color codes for the cable and for the equipment are not necessarily the same. Be careful to connect wires to the correct terminals.

3. Occasionally RF feedback presents problems. The solution is basically good installation.

4. Some transceivers (such as Messenger 124) have the microphone ground at a DC potential differing from the outer case. With a metal housed microphone there is a possibility of shorts to the outer case blowing fuses or damaging equipment. When using equipment of this type, write to the factory for instructions. Enclose a schematic and describe the problem.

5. Some transceivers are wired so that microphone input is also receiver audio. The microphone preamp (T-UG8 etc.) presents a short circuit to microphone output during receive mode.

If, when the microphone preamp is connected to the transceiver, receiver output drops to zero, cut the WHITE cable lead at the terminal inside the microphone base. Receiver volume will go to normal. Install a ~ watt composition resistor in series with the WHITE lead where it was cut. Try several values to determine the smallest value resistor that can be inserted without appreciable effect to receiver performance. Install this resistor permanently.

6. On initial setup it is a good practice to turn gain completely down. After turning on the transmitter, slowly turn the gain up until desired modulation level is reached. This procedure aids in getting gain properly set without going through periods of excessive distortion and over-modulation.


TU-Kit Wiring Diagram

TU Kit