Juma TRX2A Low Mic Gain

[KH2BR]

I cannot find where to adjust microphone gain. I have adjusted SSB Gain R26 to Max, but only get one watt output.
Input is set to Mic. I have 0.9 volts on the electric mic hot side. All the voltages around the Mic amps are good.
Cw transmit is good. Documentation states that Mic gain can be adjusted but Where? I can hear the audio in another receiver, whistle my brains out in the mic till my face turns blue. but still only one watt. Please can someone help.?

Robert KH2BR

[OH7SV]

I have 0.9 volts on the electric mic hot side

Robert,

Something is wrong with the electret mic biasing or in the mic or in the wiring.
The mic "hot side" voltage should be much more than 0.9V. Typical electret mic current is 200uA...300uA. That means 3V...4V on mic hot side.

Please check on the TRX2 main board the correct resistor values of R61, R62 and especially C46 polarity
What is the hot side voltage if you disconnect the mic?

Ps. The mic gain can be adjusted (if needed) with R1 on the TRX2 main board. But first you have to solve the problem which after it is not likely that you need any mic gain adjustment.

73 Matti OH7SV

[KH2BR]

Thank You Matti,

The Microphone element was installed backwards and now the radio functions 100%.

73's, and Happy New Year

Robert KH2BR

[OH7SV]

Robert,

Good to hear that

Readjust now the SSB gain trimmer R26 for 10W peak RF ouput. Typical proper value is in the middle position approx 25kohm which can be measured with ohm meter when TRX2 is OFF.

Enjoy QSOs with your JUMA TRX2.

Happy New Year
73 Matti OH7SV