[CQ-Contest] LTA IC-765 CW Sidetone Board

k4ro at k4ro.net k4ro at k4ro.net
Thu Feb 19 19:54:51 EST 1998

I recently installed the LTA IC-765 CW Sidetone Board, and
am having problems getting it to work.  Since LTA was sold 
to Radio Bookstore, there is no longer any official support
for this product.

Is there anyone who has done this mod to the 765, and who 
might be able to help me troubleshoot the problem?  

Here are the symptoms:

The RX CW pitch works the same as it ever has.

CW TX sidetone is now fixed at a very high pitch (like 2000 Hz.)

Test Point one on the LTA board always shows MINUS 2.65V.  (-2.65V)

The CW Pitch control has no effect on TX sidetone, or on
the voltage at the test point.

I verified that the +8V, +14V, and -5V taps are OK, and the 
voltages are reaching the LTA board.

Note: The LTA board had a broken C1, which I replaced before 
installation.  No other damage was visible.

Here I am once again at the 11th hour before the contest, tearing 
my station apart.  When will I learn?  :-(

This mod took considerable time to perform, and I sure would
like to get it to work.  Any suggestions greatly appreciated.
If you want to call me with info, I'm at 615.662.5577, and 
would gladly call you back and cover your costs.  Thanks.

-Kirk  K4RO

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