Curt - OK. Ignore my last........ I was running in circles!! :-) Big surprise!
Anyway, I think I actually know what's going on now. The diode switch D8 only keys the sidetone in CW, regardless of the position of the FUNCTION switch.
In the T-4X, V11 Pin 7 (Cathode) is connected directly to ground, and the sidetone is present whenever the key is closed, or no key is inserted.
In the T-4XB, Pin 7 is UNGROUNDED in the SPOT position of the TRANSCEIVE switch by a set of contacts on that switch. THIS is what inhibits the CW sidetone in SPOT, but only in the B and C models.
So it looks like you're stuck with it! :-) Learn something new every day with this stuff. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs <www.k4oah.com> Hulett, Russell wrote:
Garey, So, shouldn't D8 be reverse biased with the key "UP" even when the switch is in the "SPOT" position, thus silencing the sidetone? The problem is, it is not. That is, the voltage at D8 is 3 volts positive and the sidetone is whining away. Maybe I'll just need to live with this, but using "SPOT" in CW mode is somewhat difficult because the sidetone is as loud as the spotting signal. If that is the way it was designed, so be it. My T-4XB doesn't work that way, only time it's sidetone is audible is when the key is down. Thanks again, and 73, Curt KB5JO
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