How to troubleshoot AM TX humming.


  1.  Unhook your Audio going to the transmitter.  Listen to your station and see if you hear any humming with the transmitter running with no audio hooked up.  If it goes away then the hum is not from the transmitter, but from the audio source.
  2.  Remove PA 1 and run only with PA 2 installed.  Listen to your station and see if you hear any humming.
  3.  Remove PA 2 and run only with PA 1 installed.  Listen to your station and see if you hear any humming.
  4.  Keep checking each PA module that you have in the transmitter.  It is possible a modulator board in a PA is causing it.
  5. Disconnect all the cables going to the PS board #2.  Run the transmitter like this and see if the hum is there.  This will tell us if PS Board #2 is causing it.
  6. Remove the PS board #2 and put it in place of PS board # 1.  Run the transmitter like this and see if the hum is there.  This will tell us if PS board #1 is causing it.
  7. Check each power supply board in the transmitter this way.  The humming can be from a power supply board.
  8. Put the PS Boards back to their original supply assemblies.
  9. Take the whole power supply assembly and swap them.  I know this is a hard task, but this will give us which assembly it could be coming from.
  10. Once the power supply assemblies are swapped, Do the same process as we did with the power supply boards.  Swap them out until we find which one could be causing it.
  11. If the hum continues, then we will need to look at the ECU Exciter Board or even the AC input.


*** SOME AM TXs YOU HAVE TO KEEP POWER SUPPLY #1 ALWAYS IN FOR THE TX TO RUN.