unknown schematic symbol

[joshdfrazier]

i know this is definitely a no-brainer for most people here, but I've having a difficult time understanding a particular symbol on this ax84 schematic. It is a line with an arrow across the wiper terminal on the mid and bass pots:

http://www.ax84.com/static/corepreamps/ ... ematic.pdf

[beasleybodyshop]

That line is the wiper on the pot.

[LeftyStrat]

The just means that it is wired as a rheostat. That means the middle wiper is soldered to one of the outside legs.

[eniam rognab]

The just means that it is wired as a rheostat. That means the middle wiper is soldered to one of the outside legs.

or not some people just leave it hanging there, not arguing with you lefty at all, just saying "technically" it doesn't matter if you connect it or not

rheostat-old world term for variable resistor and think of it in that way. usually refers to higher power resistors where you are dealing with alot of current but it is not a voltage divider as a regular pot is capable of being.

regular pot -> rheostat if you only use two terminals

[LeftyStrat]

The just means that it is wired as a rheostat. That means the middle wiper is soldered to one of the outside legs.

or not some people just leave it hanging there, not arguing with you lefty at all, just saying "technically" it doesn't matter if you connect it or not

rheostat-old world term for variable resistor and think of it in that way. usually refers to higher power resistors where you are dealing with alot of current but it is not a voltage divider as a regular pot is capable of being.

regular pot -> rheostat if you only use two terminals

You're correct, I suppose the only reason for tying the middle to an outside lug would be in an application where a wiper failure would be bad. Like a bias circuit. If you tie it together with an outside lug and the wiper fails, it will be at max resistance rather than open.

[tubeswell]

When you use a pot wired as variable resistor for the bass control in a TMB tone-stack, make sure the wiper is wired to the 'input lug' (if you're going to connect the wiper to one of the lugs), otherwise the tone controls won't work properly

[eniam rognab]

You're correct, I suppose the only reason for tying the middle to an outside lug would be in an application where a wiper failure would be bad. Like a bias circuit. If you tie it together with an outside lug and the wiper fails, it will be at max resistance rather than open.

cool lefty! thanks for that lil bit, i havent built anything but cathode biased amps so far so this is great to know going forward!

[joshdfrazier]

So basically, you just leave it disconnected in this case. Since I didn't have those two pots, I just used resistors in place of the pots. Only had a single 1meg pot, so I used it for treble, seems to work fine so far.