Thanks Jim.? I don''t know where to look for the input to the attenuator so I better start reading the manual.? Your diagnosis is what I hope is the problem, since repairing that may not be as major.? I recall determining that the output amplifier transistors are good.
Bob
On Monday, May 30, 2022, 11:40:15 AM PDT, Jim Summers <kd7f@...> wrote:
I sounds like there may be a problem with the reverse power protection.? There are PIN diodes in series with zener diodes to ground in the protection circuit and it sounds like perhaps one of the zeners has shorted out - probably from application of reverse power above the specification.?
If you were to look at the signal at the input to the attenuator and you see no distortion at high levels (+10dBm and above) then it is probably the reverse power protection circuitry that is at fault...? It is the first thing seen coming in from the front panel connector and I believe it is in one of the attenuator enclosures.?
