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Check T5,6,7 .. it will be a solder problem or a short. Shake eaxh toroid while provinding a "hallow" in the mic
and see if the power suddenly jumps.
At 11-02-2018, you wrote:
I have a trouble with BITX40 kit from HFSignals.
Receiver work great - i hear a lot of stations all over the world. But there are no transmission when pressing PTT.
I check currencies al described in instruction (both main board power and PA power connected):
In receive mode current is 136 mA
When press PTT - 330 mA
If saying HAAAAALO to microphone when PTT pressed - the current still 330 mA and not changed.
I try to adjust PA as described in instrunction - connect ammeter directly to PA power line. First step is adjust VR1 to PA currency 100 mA. It is ok. Second step - saying HAAAALO microphone - fail, PA currency still 100 mA and not changes. I try to change value of VR136 - PA currency changes a little.
Also i try to check microphone amplifier - i connect external LM386 amp board to negative pin of C122 capacitor. When pushing PTT and saying anything do microphone - hear me from external amplifier, it means that mic amp works ok.
At the next step i connect an external continuous wave oscillator worked at 7.100 Mhz to input of PA - left pin of C132. The PA currency raise to 1 A and there is a CW output in antenna. It means that PA works.
At the next i connect continuous wave oscillator worked at 7.100 Mhz to to the right end of C43. The PA currency raise to more than 1 A and there is a CW output in antenna. It means that preamp Q4 also works.
I have no ideas what to check more with my equipment - i have no oscilloscope, have only digital multimeter, frequency meter (up to 70 Mhz), and a continuous wave oscillator (up to 70 Mhz).