Evan I took a good look at the schematic and I think your explanation is better than mine. ? I hadn¡¯t thought about part of the receiver TR switch being ON. ?
R217 might be on also??
That¡¯s great if those are half watt resistors!!
Thanks
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On Jan 4, 2024, at 19:01, Evan Hand <elhandjr@...> wrote:
?Hi John,
When the power switch is thrown, Q28 will turn on and allow current to flow through R203 and R204.? The sBitx program does not need to be running.? The current through each resistor will be the voltage supplied to the Rig minus a diode drop and the drain to source drop of Q28, a total of maybe 1 volt.? With a 13.5 volt supply and 330 ohms, that would be 37.9ma each or 75.8 total, or for power dissipation; it is 12.5volts^2/330ohms = 0.473 watts or almost 1/2 watt.? They will get warm but should be below the maximum power rating ( I believe they are 1/2-watt resistors).? Since these are always on, it might be a good idea to up them to 1-watt resistors.? L202 also needs to handle the current of 75.8 ma, so upping that device would be another good idea.
R201 and R202 do not have power flowing until the sBitx program is started and the transmitter is engaged.? I would not expect them to get warm until transmitting.
I checked on my V3, and R201 and R202 do get warm.? An increase in wattage might be a good idea.
Gordon still had a possible point that should be checked.? We know that the DE and now the V2 have had feedback issues that can turn on Q9.? There could be a similar issue with the V3 hardware.? Verifying that Q9 is not conducting should rule out that as the cause for your symptoms.
Above are suggestions only.? I would need to have the board in front of me to verify.
73
Evan
AC9TU
