Re: troubleshooting no TX SSB #ubitx #ubitx-help

Jerry Gaffke

Yes, if you can transmit CW then it has to be somewhere between Q6 and Q22,
since CW is transmittted by unbalancing the modulator immediately following Q22.
If the receiver works, then the three mixers and local oscillator are ok.
So if you still have trouble transmitting SSB, then it's Q6 or one of the bidi amps on the TX side,
and the bidi amps seldom give us trouble.

You could try unbalancing the modulator by injecting 5vdc through a series 4.7k resistor
at T7 pin 3 (and pin 5).  This is how we generated CW on the Bitx40:
If that does transmit CW, then it has to be around Q6.

Your 10mhz scope may just barely see something in the 12mhz IF section through Q42, 
and probably nothing at all in the 45mhz IF section at Q20,21,22.
If you wind up debugging those sections, you may need to build a diode RF probe or something similar.


On Wed, Feb 28, 2018 at 02:50 pm, John wrote:
But as CW seemed to work the first day I thought I had to look somewhere in the modulating circuitry. Have the schematics

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