Big dummy and his phase shifter

[plexi12000]

well...i have all my parts together and i'm going to attempt my first phaser.  one simple question about the 250k trim pot....how do i know when it's at the "right" setting?

is it just your own "preference" sort of thing? or is it very critical?  thanks dudes!

[mth5044]

WHAT phaser are you talking about?

[armdnrdy]

WHAT phaser are you talking about?

Wait....he did give us a clue. I think we're playing "guess the phaser."

Is there a P?

Is there an H?

Okay...I would like to buy a vowel. A

I would like to solve the puzzle.

Phase 90! Winner!

Tell him what he's won!

You get to tell the OP how to calibrate the phaser he's working on! (I should have taken what was behind door number two! Ah...different game show! Blasted!

Enough fun and game shows.

You calibrate the trimmer to get the deepest phasing. Yes...you do this by ear.
There is usually a small region of a "sweet spot."
Move the trimmer back and forth in that area until you exclaim...
Shazam! that's it!

[Jdansti]

What? Shouldn't he use an NIST traceable phaser calibrator?

[tubegeek]

What? Shouldn't he use an NIST traceable phaser calibrator?

Those are sold on the 4th floor and the elevator isn't working.

[Mark Hammer]

What Larry said, except that I'll suggest setting the speed for medium slow -  maybe around 1hz - so that the sweet spot will be more apparent.  Too slow or too fast and it's hard to hear.

[jimilee]

Isn't it the most even sounding rather than the deepest? Either way, once the OP turns it on and messes with the trimmer, it's pretty obvious

[armdnrdy]

Isn't it the most even sounding rather than the deepest? Either way, once the OP turns it on and messes with the trimmer, it's pretty obvious

Please explain what you mean by "even sounding."

[jimilee]

The "rise and fal"l of the shifting itself for lack of better term.

[Mark Hammer]

A bit of both, actually.  The bias control will move you into a range where the JFETs sweep nicely to beyond that range.  Between those two boundaries/extremes, you can actually achieve a number of different useful "flavours", from gurgly to swirly, enough that some might even want to panel-mount the bias control. 

A more useful mod, since the bias trimpot is only useful within a limited part of its range, is to vary the value of what is normally the 1M resistance coming off the wiper of the trimpot....after one has set the trimpot for the lowest good sweep.  The changes to the current-limiting resistance from the trimpot wiper will move the sweep range/offset around from that point.

One can either replace the 1M resistance with a 680k-750k fixed resistor in series with a 500k variable resistor, or replace the 1M with a 1M2 resistor, and use a 3-position toggle to put none, or one of two other values in parallel to get three different ranges.  Parallel values of 5M6 and 2M2 should get you stock and 2 different ranges above and below that.

[plexi12000]

oh----sorry!!     phase 45  -i get talking faster than i can think!