Ross Phaser - Very low effect volume

[jbgron]

Hi guys,

I just built the Ross Phaser from Tonepad, I used LM13700 instead of LM13600, everything else is standard.  The effect works perfectly but the output volume is only about 10% of what it should be.  I've checked all component values, swapped opamps and even replaced the 1uF output cap but the problem still persists.  Any help or pointers in the right direction would be much appreciated.

Cheers

jbgron

[GibsonGM]

Sounds like it's time to audio probe the circuit!  Find out where it gets really quiet, or fails to be boosted back up to proper level, that will be a start...

[Mark Hammer]

One possibility is a solder bridge somewhere.

I often recommend to people to take something like an old toothbrush, and some methyl hydrate, and use that to dissolve the leftover flux on the copper side of the board.  The flux is certainly safe to leave there, but often the way that light bounces off of it, it becomes difficult to spot the difference between an unintended solder bridge and simply a spec of dried flux.

Also, is it possible that you misread, and subsequently "mis-installed", a resistor value somewhere?  Say, in poor lighting, a 270k unit sort of looks like a 27k unit?

[jbgron]

Thanks for the tips guys, I'll certainly probe and look for solder bridges when I get home from work tonight.  I think it could be a short somewhere, I noticed last night that the battery got really hot, almost too hot to touch.

This is also the first time I used this circuit board lacquer, http://jaycar.com.au/productView.asp?ID=NA1002  I hope that hasn't got something to do with it...

[jbgron]

After checking for solder bridges I got out my probe last night and started probing the circuit, strangely the board seems to be receiving the input signal at the same super low level as its outputting.  I have to turn my amp right up to hear it.  Being a confused noob, I replaced the input jack and switch and also re-soldered the input wire but the problem still persists. 

Does anyone have any idea as to why the board would be receiving such a low volume signal??  I'm totally baffled. 

[Wieslaw K.]

I did make this phaser few months ago and had similar problem. In my case it was bad value of first capacitor (100pF ) between signal path and ground. So, maybe you should check such basic things once more.

Sorry for my poor English. I'm from Poland and I'm no so fluent in it. However, I read this forum almost every day and steel under impression of your knowledge and experience, guys. 

[jbgron]

I got it working!  Turned out to be a dodgy output jack, wish I had of thought of that first 

Lovely phaser, very "liquid".