[TenTec] Argosy 2

[William Redfearn]

Well, that's different :-)
If U1, pin 1 is <3 volts in other than CW mode, take a look at Q4.
If Q4 is turned on (by the CWU line) or shorted, U1, pin 3 will be grounded thru D2 & R15 which unbalances the balanced modulator to produce the CW carrier.
This sounds like what is happening from your description.
For troubleshooting, you could unsolder and lift up one end of R15, isolating the balanced modulator from the CW switching circuitry and see if the U1, pin 3 voltage returns to normal for the SSB modes and troubleshoot U1 or Q4 as needed.
The description of the SSB Generator board is not too detailed but you can get an idea of what the switching is doing.
Troubleshooting from afar is not too easy :-)

73 - Dave, N4ELM  

"The voltage levels on the 4558 appear to be correct, I have changed it
anyway but the voltage on U1 pin 1 is only <3v not what is written, all
other pin voltages are correct."