Stomptown Phase 45 Issue

[Zigcat]

It works kind of. I can hear phasing but it seems like Q2 doesn't do anything(matched pair of 2n5457 reversed orientation from 2N5952) and the blend pot is most intense in the middle position. I can't see any solder bridges or obvious errors. Any help debugging this thing would be greatly appreciated.

-Andrew

[Luke51411]

We need more info. Why do you think it's not working, is the phase really weak? The p45 is a fairly subtle phaser. It would help if you check out the troubleshooting thread. Post pictures of both sides of the board and take voltages at all IC and transistor pins and post those.

[Luke51411]

http://www.madbeanpedals.com/forum/index.php?topic=902.0

[Zigcat]

I'll get voltages and pics up in a couple days. I know it a subtle phaser but q2 can be completely removed and the sound is not affected.

[Leevibe]

The blend pot will be most intense in middle position, so that is correct. I have a working trailfazer Galacticon DX board with 2N5457s. Just to verify, the flat faces of the jfets should be looking at each other.

[Zigcat]

Well the blend pot was my greatest concern. So only half the sweep does anything? That's pretty odd and not very intuitive. I was expecting different results based off blend controls on other effects.

[Luke51411]

It sounds like you have other issues. The effect would probably be most intense in the center with equal vol dry and phased signal. At one end you would get dry and the other end a vibe effect. You need to figure out what's going on with Q2 check for solder bridges or cold joints in the area.

[Zigcat]

Yeah. That's what I'm thinking. Q2 is definitely suspect. I'll look at it early in the week after I do the Mother's Day thing.

[Stomptown]

Well the blend pot was my greatest concern. So only half the sweep does anything? That's pretty odd and not very intuitive. I was expecting different results based off blend controls on other effects.

I think there is a bit of confusion as to what the blend knob does, and like you said, it's not all that intuitive.  You'd think the blend would go from subtle to in your face but it's actually just changing the ratio of wet to dry signal as you move away from 12 o'clock.  I honestly I don't find the blend control to be that useful but other people who enjoy bells and whistles seem to like it. I am probably going to start offering the stock phase 45 version again for those who wasn't the streight up P45 sound.  Definitely check Q2 but realize that it is fairly subtle even at the mid point.  I also suspect that using a 25k pot affects the intensity even at the mid point so it's probably a bit more subtle than the stock P45 (assuming you were unable to source a B20k pot).

Edit: I've built 2 of these now; one with a B25k and one with a B20k and the one I built with a B20K seems closer to stock iirc.

[Leevibe]

I would try setting the blend pot at 12:00 and very carefully adjust the bias trimmer for maximum depth. It could be the trimmer just needs to be tweaked.

[Stomptown]

It sounds like you have other issues. The effect would probably be most intense in the center with equal vol dry and phased signal. At one end you would get dry and the other end a vibe effect. You need to figure out what's going on with Q2 check for solder bridges or cold joints in the area.

This I'd actually not correct.  Here is how it works:

Center: full phase standard(ish) P45
Clockwise: brighter and less phase
Counterclockwise: darker and less phase

[Stomptown]

I would try setting the blend pot at 12:00 and very carefully adjust the bias trimmer for maximum depth. It could be the trimmer just needs to be tweaked.

This for sure!  And I would also bias in phase mode (toggle to the left).

[Luke51411]

It sounds like you have other issues. The effect would probably be most intense in the center with equal vol dry and phased signal. At one end you would get dry and the other end a vibe effect. You need to figure out what's going on with Q2 check for solder bridges or cold joints in the area.

This I'd actually not correct.  Here is how it works:

Center: full phase standard(ish) P45
Clockwise: brighter and less phase
Counterclockwise: darker and less phase

Well... That's what happens when I assume without even looking at the schematic.

[Stomptown]

Here are my voltages for comparison:

Q1 and Q2:
  G:1.78-1.94 (variable)
  S: 4.39
  D: 4.39

IC1:

  1: 4.39v
  2: 4.39v
  3: 4.18v
  4: 1.2 mV
  5: 4.38
  6: 4.38
  7: 4.38
  8: 9.4

IC2:
  1: 4.38
  2: 4.38
  3: 4.37
  4: 1.2 mV
  5: variable
  6: variable
  7: variable
  8: 9.32@

[Zigcat]

Awesome. I'll compare these with mine very soon. If I could bring my DMM and iron with me everywhere and not look weird, I would. Sometimes I hate being away from home. Sitting at a restaurant with a meter and one of those crappy butane irons Rat Shack used to sell... That would be something to see:).