total noob first post help with dallas range master

[tonefiend]

Hello Everyone,

first post here,  so pardon my total ignorance, im just learning and had a total noob question.    I want to build a dalllas range master clone, and I was reading the fantastic article written by R.G. Keen on the "austin treble blaster"  and the part where he talks about biasing the transistor by replacing the 68k resistor and 3.9k resistor with a 100k, and 10k pot respectively, to get the -7v on the collector...  im actually going to build the NPN version so I beleive I will be trying for +7v on the collector...   anyhow, my new guy question is how do you connect the pots to the circuit?   Im not sure what lug goes where....   Here is a random guess, which might be totally wrong, but for the 100k pot, replacing the 68k resistor, would the wiper (lug 2) go to the bottom of the 470k resistor, and lug 1 to positive voltage and lug 3 to negative?  and for the 3.9k, wiper (lug 2) to emitter, lug 1 to pos, lug 3 to neg. ?        Also when tuning the transistor, where do you set the 10k pot going to the collector?  full on?  full off?           please as a side note, I did do a search on this and couldnt find the exact answer I was looking for....

thanks in advance for any help in clarifying this for my new brain...          and many thanks for this forum,  really looking forward to this build

[midwayfair]

You wire the pot the same way as in the schematic.

When building NPN vs. PNP, the only difference is in reversing the polarized components: electrolytic capacitors, some diodes, and the supply voltage. Electrolytic capacitors need to have the + side facing the side with the higher voltage ("0" ground is higher than "negative" in PNP circuits). Any diode that is acting as polarity protection will need to be reversed to make it work properly when the power is hooked up correctly. The supply voltage connection needs to be oriented to provide the proper side to ground ("negative" for "negative ground" and "positive" for "positive ground).

Resistors, potentiometers, non-polarized capacitors, and pieces of wire do not have polarity and their orientation doesn't matter.

Finally, the part you are talking about is simply wiring two different pots as a variable resistor to temporarily replace two fixed resistors. (See: http://www.geofex.com/article_folders/potsecrets/potscret.htm). The wiper and any outside leg of a potentiometer form a variable resistor. You hook up the pots to the same connections as those two resistors in the circuit. The order you wire them does not matter unless you care about the direction the pot rotates (which shouldn't matter because you're going to use fixed resistors for those pots once you've figured out the best values) -- there are only two connections.

[tonefiend]

thanks for the help...     and link to the pots information very helpful indeed...   

would you also possibly know the answer to this part of my question:

"Also when tuning the transistor, where do you set the 10k pot going to the collector?  full on?  full off?"


thanks very much   

[slacker]

For tuning the transistor it doesn't matter where you set the boost knob, it's position doesn't affect the DC voltages.

[gjcamann]

It doesn't make a difference. If you look at the schematic, it will look like a resistor (with an arrow) going from V to the tranny. The arrow is the tap point for the volume (as you turn the pot, you move the arrow up and down the resistor, the closer to V, the less volume you'll have), it has no effect on the amount of current going through the tranny.

Good luck!

[tonefiend]

Finally, the part you are talking about is simply wiring two different pots as a variable resistor to temporarily replace two fixed resistors. (See: http://www.geofex.com/article_folders/potsecrets/potscret.htm). The wiper and any outside leg of a potentiometer form a variable resistor. You hook up the pots to the same connections as those two resistors in the circuit. The order you wire them does not matter unless you care about the direction the pot rotates (which shouldn't matter because you're going to use fixed resistors for those pots once you've figured out the best values) -- there are only two connections.
[/quote


Hello,  I still need some clarification to understand where to put each wire of the pot...   so if I put a wire on the wiper(lug2) and a wire on any outside lug (lug1) where do i connect those wires in the circuit?  does it matter?     For Example using the 100k pot that replaces the 68k resistor,  do I connect the wiper lug2 to the bottom of the 470k resistor, and lug1 to ground,  or the other way around?  Sorry just trying to get my head wrapped around this one..   

thanks for the help

[peterg]

Finally, the part you are talking about is simply wiring two different pots as a variable resistor to temporarily replace two fixed resistors. (See: http://www.geofex.com/article_folders/potsecrets/potscret.htm). The wiper and any outside leg of a potentiometer form a variable resistor. You hook up the pots to the same connections as those two resistors in the circuit. The order you wire them does not matter unless you care about the direction the pot rotates (which shouldn't matter because you're going to use fixed resistors for those pots once you've figured out the best values) -- there are only two connections.
[/quote


Hello,  I still need some clarification to understand where to put each wire of the pot...   so if I put a wire on the wiper(lug2) and a wire on any outside lug (lug1) where do i connect those wires in the circuit?  does it matter?     For Example using the 100k pot that replaces the 68k resistor,  do I connect the wiper lug2 to the bottom of the 470k resistor, and lug1 to ground,  or the other way around?  Sorry just trying to get my head wrapped around this one..  

thanks for the help

All 3 pot lugs should be used.
Take a look at the attached page for more info on pots and the Trimmer Resistor section in particular: http://www.beavisaudio.com/techpages/Pots/
Try experimenting:
1. Attach the wire from Q1 base to lug 1 and the ground to lug 3.
2. Attach a small wire to lug 2 and attach the other end to lug 1.
3. Rotate the pot to see what happens.
4. Remove the small wire connection from lug 1 and connect it to lug 3.
5. Rotate the pot to see what happens.
6.Select which option you like.