JT,
If you have little or no RF output, do not be concerned about the early
stages having more RF voltage than is expected when the power is normal
(and that is your case). Continue onward.
If the K2 senses no power output, VPWR will ramp up to a high level
trying to obtain more power output, and the RF voltage produced by the
*working* stages will be higher than normal until the proper amount of
RF is detected at the output.
An added note - measure the RF voltage across your dummy load. If there
is lots of RF voltage there, then the transmitter is working and the
problem is with the detector (D9 and associated components) rather than
the transmitter stages, but if there really is no power output (or very
little) then look to the transmitter stages for the problem. - Do heed
the *if*s in the proceeding statement, they are very important.
Make the measurements in order and methodically as instructed in the
manual and the steps will lead you to the failing stage.
73,
Don W3FPR
JT Croteau wrote:
Don and others,
I just returned from buying a new DMM at RS and I didn't get very far
in signal tracing the transmitter before I started getting some
strange readings.
In my previous email, I mentioned that VPWR was reading high at 4.9V.
This can sometimes point to a problem in the RF output detector so I
checked all the components here and didn't find anything wrong so,
following the instructions, continued on with the signal tracing.
Transmit Mixer, Buffer, Band-Pass Filter, T-R Switch section - I am
finding some odd voltages here. Voltages that do not match the
expected results listed.
These are all key-down voltages.
Xmit Mixer Output: 0.181 (Expected: 0.016)
Buffer Output: 2.05 (Expected: 0.200)
Band-Pass Filter Output: 0.444 (Expected: 0.030)
T-R Switch #1 Output: 0.439 (Expected: 0.029)
I am doing the signal tracing using 40M.
Do I need to worry about these?
Thanks
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