On Tue, Apr 8, 2025 at 02:11 PM, WB9YXA wrote:
What bothers me is that the output power seems to jump around wildly.? If I go to the diagnostics screen and key the transmitter, the Bias SMPS shows fluctuations in current that correspond to the fluctuations in the output power.?
There could be many causes for this.? Some are assembly-related, some are board smd soldering issues, and it could also be a failed component or bad port on the processor.
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Here are some of the assembly-related things to check for bias current issues, via inspection and your multimeter:
- Make sure L504 and L514 (two of the through-hole inductors you put in) are properly soldered, and not cracked.? This type of inductor is a bit fragile, and it is easy to break them with a little too much force.
- Make sure your diodes are all installed the correct direction.
- Make sure L501 (the small 330uH coil) has not been broken from the board during assembly.
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Some board SMD soldering issues to check that affect bias current:
- make sure C504, the large tantalum SMD capacitor, is properly soldered on both ends.? Also test that it is not shorted internally.? Jeff W1NC said he has found C504 soldering issues and failure in some boards he has repaired.
- verify the soldering of Q501, Q502, and Q516.? One user found that Q516 was poorly soldered.? You need to check these under good magnification.
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Hopefully one of those will hold the solution to your? particular problem.
Good luck, Stan KC7XE
