[TenTec] More Omni D problems

[tfr001 at myfairpoint.net]

Hi all,
More problems with my Omni D.
It has this intermittent problem where both TX and RX will sort of go away... RX gets very deaf and TX goes very weak - only some mW output. It is somewhat sensitive to shock - in the form of dropping the rig about 1" onto the bench. This seems to make the problem come and go, sometimes.

After much troubleshooting, I think it's down to the RX mixer board. The output of this board (named "IF") goes to the noise blanker input socket (not installed on my rig), is jumpered to the output socket, and from there to the xtal filter and the TX mixer. The "IF" signal itself seems rather weak (maybe 50 mV pk), ugly (very spikey looking, not at all a sine wave), and it goes completely away when I switch to TX (via the Mode knob). All inputs to the RX mixer board are good - from the VFO (named "LO"), the T/R signal (named "R"), and 12V power. I tried pulling both the xtal filter and the TX mixer boards in case one of these was shorting the signal out... nope, no change. I checked all of the inter-board wiring as best as I could, found one crappy solder joint, fixed it, no help there either.

Not sure where to go from here... about the only things on that board which might be vibration sensitive are a couple of the transformers wound on multi-hole beads... they kind of flop around, dangling from the wires. This is considered bad practice at every place I have ever worked... usually such things are "staked" to the board with some RTV or hotmelt.

Any advice appreciated!
-Tom R. N1OOQ