Hi,
The counter 'MODE' switch simply switches it between the output of
the tracking generator and the external socket, so if it works
only on 'EXTERNAL' you probably have a fault with the generator
and not the counter. Try looping the RF output (at about 0dBm)
from the 8443A into the counter input, switch to external and see
what you get. You should see a varying display as the analyzer
sweeps. If you don't get anything, there is a problem with the
tracking generator or the outputs from the 141 itself. My money
would be on the crappy cable, plugs and sockets on the back of the
unit.
If it isn't them, remember that the 8443A just mixes together
several signals from the 141T, filters them and outputs the
leveled result from the front panel so it is not difficult to
track down problems. All of the boards come out quite easily so
that you can work on them on the bench one by one. I don't know
what test gear you have but a scope and a signal generator would
help. Just follow the block diagram (Fig 8-19) in the manual.
Cheers - Joe G3LLV
