silver sabre battery check

[Pete B1]

Hi, could someone please help a noob by identifying which components comprise the battery check circuit on the Silver Sabre plus.
I have the schematic, but still trying to get my head around it

[Merc]

I have circled them. You can see the 10uF tantalum near the voltage regulator.

[simonbaker]

ICL 7660

Does the ICL 7660 run at a different oscillator frequency than the TX oscillator, or is it somehow coupled?

Is the ICL 7660 oscillator used to generate the audio tone rather than the TX oscillator (through the .015 uF capacitor)?

Regards,

-SB

[ApBerg]

Does the ICL 7660 run at a different oscillator frequency than the TX oscillator, or is it somehow coupled?

Is the ICL 7660 oscillator used to generate the audio tone rather than the TX oscillator (through the .015 uF capacitor)?

Regards,

-SB

Correct ! The 220pF is leading.. changing this 220pF gives an other audio freq.
(if I remember well...)

Regards.

Ap

[simonbaker]

Correct ! The 220pF is leading.. changing this 220pF gives an other audio freq.
(if I remember well...)

Regards.

Ap

Interesting, the spec shows you should connect the cap to ground, but I guess V+ and ground are both ground as far as AC is concerned.

The spec also indicates you can drive the oscillator externally. Seems that might be desirable to make sure stray oscillator signal does not corrupt the synchronous detector operation. Wonder why they didn't do that? Probably because it would require a divider circuit, another component, in order to generate the right audio tone.

Might be interesting to try to use the 7660 as the TX oscillator with an amplifying transistor...

-SB

[Pete B1]

Thanks for the reply Merc. I did manage to locate this circuit on the board.
With this circuit removed, and the trimmer replaced with an external pot, it frees up a lot of space