[TenTec] OMNI VI+ BFO Brainteaser

[John Clifford]

The amount of frequency change would also be interesting.  You are assuming
that the freq is shifting by the amount of the CW offset, but have you
verified this?  If this IS true, then you are NOT switching in to CW xmit
mode, because the shift is a lot more than 400 Hz (about 2600 Hz actually...
there is other stuff going on during xmit that negates this shift down to
the CW offset).

It wouldn't hurt to check to see if there were any cold solder joints on the
BFO trimmer caps by re-heating them with a soldering iron (you will have to
remove the board).  You might want to also re-align the BFO trimmer caps...
maybe some oxidation has developed and rotating them back and forth will fix
any intermittancies, but you will need to re-align the rig using a
calibrated frequency counter.  Before going thru the alignment, you could
attempt to verify this (intermittancy) by tapping on the BFO trimmers with a
ceramic adjustment tool to see if you can repro the problem, or make it go
away when it happens.  But alignment really is simple IF you have a
frequency counter.

The only way you could verify whether your rig is indeed switching BFO xtals
would be to put a probe on the CW Xmit line coming in to the board, and
seeing if it is switching high when you see your symptoms.  If this is
happening, I'd send the rig back to Ten-Tec.

I would do the following, in the following order, until the problem went
away:

. re-align the BFO xtals via the trimmer caps, after putting a little
De-Oxit on the caps and rotating them several times back and forth thru
their entire range

. pull the BFO board and touch up the solder on the BFO trimmer caps (and
any other questionable solder joints on the board)

. send the rig to Ten-Tec

Good luck, and let us know what the resolution is,

 - jgc

John Clifford KD7KGX

Heathkit HW-9 WARC/HFT-9/HM-9
Elecraft K2 #1678 /KSB2/KIO2/KBT2/KAT2/KNB2/KAF2/KPA100
Ten-Tec Omni VI/Opt1, Centaur, 238B
Alinco DR-605TQ, DJ-V5
Icom T90A

IRLP #3978

email: kd7kgx at arrl.net