Aaron,
Verify that you do not have the "skewed pot" issue pictured in the following message:
/g/BITX20/message/73189If that is the problem, then most likely you will have to replace one of the finals.? IRF510s are relatively cheap and readily available.
After the visual inspection, I would validate that the Bias regulator is delivering 5volts when the PTT is pressed and that there is a gate bias on each of the IRF510 output transistors.? All of this should be done into a good 50ohm dummy load rated for at least 10 watts.? The 20watt QRP-Labs dummy load is a good low-cost dummy load for up to 20 watts at only $8.50 plus shipping
The last test would be to readjust the bias on the finals to verify operation.?
REMEMBER that the pots are
REVERSED.? Minimum bias (current) is fully
CLOCKWISE? You turn them counterclockwise to increase the current, being VERY careful not to exceed 150ma for each device.? Here is the HF Signals bias settings page:
If you can adjust the bias, then most likely the finals are OK.? The next most vulnerable device in the chain is then Q90.? This transistor has been know to be blown by nearby high power transmitters.? There is a recommended back to back diodes (1n4148 as an example) from the switched antenna lead on K1 pin 12 for the receive section to ground.? This will not affect receive sensitivity, yet protect when a high power transmitter keys up when in receive or powered down.
The above are just suggestions.? You should review the schematic and do the measurements to validate before making the mods.
Good luck hunting down the issues.
73
Evan
AC9TU
