Extend ground balance to salt Bandido II uMax

[Goodrat]

Trying to initiate this discussion again.
There was a suggestion to add a 47K in series with the 50K pot, and use a .001 cap from that junction to ground. Another (Dave?) said it works on Spice. This seems to however make the pot work backwards when switching in the cap for a wet salt mode.
Try this: No additional resistor, take the unused end of the pot and connect a 1000pF to ground. This seems to operate correctly and without having to use a switch for either mode. Although further shifting may be required by adding a switch right after the 10K going to the op amp to ground with another 1000pF.

For those not looking at the schematic, there is a 180pF going to wiper 50K GB pot, CW leg to a 1K to ground (CCW is 51K), wiper also to 10K then to op amp (393) inverting input.
CW will be 90 deg, CCW will be 60 deg. We want the 60 to reach zero or probably cross over another -45 deg.
Adding the 1000pf to the pot CCW to ground should still get close to 90 cw and zero ccw.
(I need spice, this is getting dificult). Add another 1000pF to the op amp input and you can cross the additional 45 deg.

[Goodrat]

Note

The cap can be across the 50k pot rather than ground for easier assembly.

[Goodrat]

Still not far enough. Trying this now.




This willget an additional 35 degrees than my last attempt. Field testing soon.

[Goodrat]

Hold everything. This works!




Needed to go at least +30 degrees.

[Marcello]

Re: Still not far enough. Trying this now.

Do excuse me, would you know how to tell me the values of the capacitors XX marked by Carl on the circuit of the BandidoII?
thanks

[Carl]

Re: Hold everything. This works!

I will definitely give this a try, as soon as the swelling goes down in my hands. Right now, I can't even hold a pencil.

- Carl

[Carl]

Re: Still not far enough. Trying this now.

Most of the caps in Tesoros are SMD chip caps. I used an LCR meter to measure them, those marked XX are ones I could not measure reliably. Compare to other Tesoro schematics that have been posted, you can probably figure them out.

- Carl

[Goodrat]

Re: Hold everything. This works!

I haven't heard, did you get hurt?
Anyway the discrimination and depth seem to work fine in the salt mode. The falsing from the salt is gone! The only thing strange is that I am picking up small bits of iron that we find on the beaches here.
Possibly in this balance range, there is no way to discrim out the iron?

[Marcello]

Re: Still not far enough. Trying this now.

Thanks Carl, but there are probably some errors, for instance c7, c5 and c42.
Would you know me to say the correct value and the correct polarity?

[Carl]

Re: Bandido errors

C5 & C42 definitely look flipped, pos. side should be to ground. C7 looks fine, if it's polarized then pos. side up. If you thought the value was too high, IC3 is the battery "check" circuit -- turn the machine on, and IC3 blasts the audio until C7 charges up and shuts down the TX gate. An incredibly annoying way to check a battery.

I modified the circuit to drive a bicolor LED, red if B+ is lower than 6v, green if higher.

- Carl

[Goodrat]

Anyone?

I need some ideas how to cure the iron problem when I shift the GB so far.