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Turner Expander 400 mic
- Thread starter H1driver
- Start date
I wired it up per the above and on My mic tester it shows the green rx light on and the red tx light when keyed, but no audio. The cord appears to me to be the original. I do have an extra yellow wire. Here is a pic of the guts if it helps. The white wire and shield are down near the bottom. New 9 volt battery. I am not 100% the mic works, I bought it used. Any ideas? Thanks.
The extra yellow wire in the cord was for Johnson CB radios. No other brand needed that wire.
That mike has a built-in modulation meter on the front. Does it kick around in step with your voice, or does it just lay down at zero?
73
That mike has a built-in modulation meter on the front. Does it kick around in step with your voice, or does it just lay down at zero?
73
That explains the odd shape of the circuit board. Been too long since I looked inside one of those.
Next thing to try is to lay one finger on the shaft of a small screwdriver and touch the tip to the preamp input on the circuit board. Of the two wires coming from the cartridge to the pc board, one is ground, the other one 'hot'. Touch the tip to that side and see if you can hear a hum coming out of the mike when it's keyed.
No hum suggests an amplifier problem. And if you do get the AC hum audio, this points to the cartridge as the trouble.
73
Well I do get a hum from the mic tester when I touch the white wire. I dug out the other two of these I have and one of those does the same as this one, the other works great, so I know the wiring is correct. Of the two that do not work, one looks to be NOS and the other is typical used. The mic cartridge is inside a plastic “box” that creates the front of the mic. See pictures below.
one difficulty Is the mic cords, the wires are fragile, difficult to strip. The shield wants to just fall apart when you try and twist it up. Should I try new cords first?
what would be more likely to fail, something on the boards or the mic cartridges? The cartridge is 1-1/2” is diameter, is that similar to any that are currently available?
any help and/or suggestions is much appreciated. Thanks!
one difficulty Is the mic cords, the wires are fragile, difficult to strip. The shield wants to just fall apart when you try and twist it up. Should I try new cords first?
what would be more likely to fail, something on the boards or the mic cartridges? The cartridge is 1-1/2” is diameter, is that similar to any that are currently available?
any help and/or suggestions is much appreciated. Thanks!
To the best of my knowledge the cartridge is ceramic. Probably pretty rare by now.
A 'scope probe across the black and white wires on the cartridge would reveal if any audio signal comes out of it when you hold it close and shout into it.
73
A 'scope probe across the black and white wires on the cartridge would reveal if any audio signal comes out of it when you hold it close and shout into it.
73