There are not many parts in those filters. If you draw out the schematic
by looking at the PCB traces you can reason out which parts could fail
in a shorted mode, or in an open circuit mode, and cause complete loss
of signal throughput. (If you do this exercise you will no doubt realize
that some of the components could fail changing the filter
characteristic, without making the signal throughput go away
altogether.) One you have decided which components could cause total
loss of signal, then consider the likely modes of failure based on what
you know about the components. I would hazard to guess that them most
common failure mode of crystals is open circuit, when one lead breaks
off from the plate on the side of the quartz crystal. For disk ceramic
capacitors ( that is all I have seen in the Ten-Tec filters) I would
guess that short circuit would be the most common failure mode, but at
the voltages and currents these things are subjected to in the IF of a
radio, it seems unlikely they would ever fail.
You could short circuit the series crystals one at a time to see if
signal comes back. Of course you will not have the proper bandpass
characteristic while doing this.
The other possible cause is a failure of connections between
components.This I would guess is more probable than component failure.
Reflow all of the solder joints, and make sure the pins are clean. Then
try again.
73 DE N6KB
Does anyone have any insight into problems (and solutions) that would cause
failure in a Ten Tec model 282 (or any other similar model) crystal filter?
When the unit is plugged into its slot (on a Corsair) we get no response. Our
next step is to test it on a network analyzer but I felt it would be worthwhile
to also get inputs from people on the reflector.
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