Cibola modification question ~

[pinenut]

Hey folks, I just bought a Cibola to modify. Not because I needed one, but just because I wanted one to modify with a ground balance, and possibly a pinpoint toggle (replacing the button, but mounted underneath). I've read that when using a 10 turn pot for GB, that the balance point is often toward one end of the ten turns, and not at around five turns, or the middle of the range. Is this always the case, or dependant on the particular potentiometer that was used (linear or audio taper..)..? Might it be possible to get the balance range centered by adding the correct value resistor either in series or parallel with the ten turn pot?
Any thoughts?

 

[ArizFlash]

Here's a link that provides some info for the Cibola mod

http://www.findmall.com/read.php?22,1524752,1553004#msg-1553004

 

[pinenut]

Thank you for that link, ArizFlash.

 

[pinenut]

Another question... Has anyone used a brand of precision pot for GB, other than the obligatory Bourns brand? I see a couple other brands of precision, 50k 10-turn pots of suitable size, and similar (and lower) price.

 

[ArizFlash]

Bourne is good. Use 1/4 watt with a minimum of 5% tolerance. 1% tolerance is 500% better. The shipping and handling is expensive. Mouser is a good vendor.

 

[pinenut]

Mouser seems pretty expensive. This looks like the right pot, and they don't get much cheaper...
Thoughts?

Bourns 50K 10-turn Pot

 

[Kmaz]

I myself would not buy one that ships from China.... I could be wrong but I'd assume that there knock offs.
Kris

 

[Sven]

Will tell you right now, you can buy the Chinese Bourns and they work just as well as the Bourns.
The nice thing about the China ones is they have end stops at 10 turns, all others have continuous turns, the end is when the turning gets just a bit stiffer.
Most won't notice that and keep turning. Ever wonder why some have problems adjusting the Garrett Scorpion?

You can also find surplus Clarostat 10 turn pots, they come up now and then. Just make sure its the right value, they have end stops.
http://www.ebay.com/itm/NEW-CLAROSTAT-RHEOSTAT-10-TURN-73JA-100K-OHM-POTENTIOMETER-/381773349353?hash=item58e37701e9:g:zbcAAOSw4shX2qLj

Might as well face it, most electronic parts are manufactured in China, some parts manufactured in China, shipped to Mexico and assembled stamped Made in Mexico.
What a scam.

There's also these http://www.ebay.com/itm/BECKMAN-HELIPOT-PRECISION-10-TURN-POTENTIOMETER-S7286-R1K-L-25-NIB-LOT-OF-1-/250981361259?hash=item3a6fa7a66b:m:moxxKbFEoJdopF4jsz3MYvQ

http://www.ebay.com/itm/POTENTIOMETER-COPAL-M22E10-1K-OHM-10-TURN-/231720824320?hash=item35f3a32e00:gAAAOSwA4dWHsGO

 

[pinenut]

Will tell you right now, you can buy the Chinese Bourns and they work just as well as the Bourns.
The nice thing about the China ones is they have end stops at 10 turns, all others have continuous turns, the end is when the turning gets just a bit stiffer.
Most won't notice that and keep turning. Ever wonder why some have problems adjusting the Garrett Scorpion?

You can also find surplus Clarostat 10 turn pots, they come up now and then. Just make sure its the right value, they have end stops....[/url]

Thanks, Sven. Doesn't matter to me if they have the stops or not, but I guess that having 'em is a plus. What matters most is physical size, correct Ohm value and part quality.
I was actually looking at a Clarostat, as well as the cheap Chinese Bourns. Was thinking I'd buy enough miniature on-off-on-momentary toggles, and enough pots to do a few Cibolas, or switch to 10 turn pots on some other Tesoros besides Cibola.

For the GB mod on Cibola, I do want a 50k linear taper; right?
Some Cibola people note that their balance point seems to be at one end of the GB adjustment range... Might that be caused by using the incorrect taper?

 

[Kmaz]

Maybe Bourns are sourced in China anyway. I got mine from a reputable supplier and they have end stops. Could be wrong but I believe they were part # 3590

 

[Stoof-tabsallday]

I got a genuine bourn's from mouser.com and it stops at the ends.
Pm sent to pinenut with all part numbers needed for the mod.