MXR Phase 90 mod gone wrong.

[DBDbadreligion]

Ok I was modding my phase 90 according to these mods.
http://www.aronnelson.com/gallery/v/Schematics-etc/phase_90_board.jpg.html?g2_imageViewsIndex=1

I wanted to see what they would do and how close to the script mod they would get.

I finished everything up, and plugged it in and there was no sound when effect was turned on.
I then took it back and audio probed it on every solder joint and nothing happened.
So now I am baffled and don't know how to fix it.  It makes me mad cause I really love that pedal.
I don't think it is a voltage problem, because the LED still works.

Anyone have any ideas?

Thanks alot,

Nick

[DBDbadreligion]

is it possible that static blew the IC's or a transistor or something?

[petemoore]

I then took it back and audio probed it on every solder joint and nothing happened.
  What about following the signal path through the circuit, find any places where signal stopped ?
  nothing happened = no sound anywhere ?
  Voltage measurements...unfortunately when it doesn't work and we don't know why there are a thousand and hundreds of possibilities, the debugging thread describes the processes of elimination which have proven themselves as the 'go to' method for quickest fix results.

[e178453]

I love that pedal, too! Put it back together as it was originally and see if it works?  Was it just the script mods you did?  Has anyone else done these mods?
scott

[DBDbadreligion]

no i did all the mods accept for the ones that say to switch it to a pot.  how do I determine which traces are the signal path?  sorry im still kind of a newb.

[petemoore]

  Post a link to the schematic..
  Basically you have 2 power rails, one is Gnd. one is V+.
  anything connected to DC can't be 'signal' which is AC [alternating current, as in alternating at the speed your strings alternate across the pickups...+/- swing].
  So generally the power rails go across the top and bottom, but in the 90 schematic IIRC, they also have power lines running 'into' the circuit...DC is direct current...as in steady 9v, or Vref, or Gnd. a DC reference will 'hold still' [for the most part and for discussion here] anything connected to it, so you won't get voltage swing [as in AC or Signal Path] on any DC lines.
  Could be you have to reset the bias trim after if you did any LFO Mods...?...one of those pins in the LFO will "LFO' [slowly go up and down in voltage], 'listening to the LFO..I don't think can tell you anything.
  That leaves the first stage, and all the phase stages [minus pins 4=Gnd. and pins 8=V+] on all the opamps, follow the schematic from input, through input cap, into first OA...one of the [+ or -] inputs...then it's output, the next opamp [you're using dual OA's?] would be the first phase stage, so any relevant signal path pins [not Gnd. or V] should have signal on them if signal is at input...
  Work from input to output to see if you can find where the signal stops.
  Voltage measurements on the pins 1/2 likely tells the same story about where the problem is, look for 'about' 1/2 v on all relevant signal path pins.
  IIRC there's a voltage divider and a Vref of 1/2v, and another to get a LV for the LFO...involves the zener...1/2v or Vref or Vbias should be...about 1/2v of supply, Gnd. being 0.0vdc and V+ being 9v...that'd put 1/2v at ~4.5vdc. Yupp, schematic helps.
  All this and more in the 'what to do when it doesn't work sticky thread.

[R.G.]

What to do when it doesn't work...

[Zben3129]

Sounds like you have the signal shorting to ground somewhere...

Try probing at:

The input jack tip

The pad where the input jack wire connects to the board

All positive and negative inputs of every opamp. (look up datasheets to find correct pins)

and post results

Zach

[DBDbadreligion]

ok i will try debugging tomorrow.  one thing i forgot to add was that, when i used a battery and turned the effect on you could here a clean signal wiht very low volume that had no effect change on it.  so it was just clean and no phaser.

[DBDbadreligion]

bump

[DBDbadreligion]

i put it back to the original layout and it still doesn't work.  when bypassed a full clean signal goes through and when turned on a very low volume un-effected clean signal goes through.

[DBDbadreligion]

ok i just probed the circuit again.  when the effect i turned on when the input jack tip is probed it will not make any sound.  or any other input section of the circuit for that matter.  when i probe the output jack and the output section of the circuit while the effect is on normal volume levels are let threw.  this is leading me to think something is wrong with the IC's.  When I was building my B. Blender the same thing happened and it was just that I had the wrong type of IC's in the circuit.  Maybe I need to get new IC's for this circuit, maybe they are fried.

[Zben3129]

So what you are saying is the sound that does not exist at the input is somehow generated at the output 

Hmmm...Are you sure you didn't mean you have sound at the input jack but nothing at the output jack?

Sound doesn't generally pop up out of nowhere. Guitar sounds, that is 

[DBDbadreligion]

yes i am posotive it was the tip of the output jack.

[DBDbadreligion]

but like i said some sound goes through when it is turned on, just at very low volumes.

[Zben3129]

So, just to make sure I understand you corectly...

Effect ON

Input jack tip - no sound at all

Out jack tip- some fain sound

[DBDbadreligion]

Effect Off - normal volume

Effect On

Input Jack Tip - No sound at all with probe

Output Jack tip - same volume as when bypassed.

When not being probed, effect on has some fain sound.

[petemoore]

Input Jack Tip - No sound at all with probe   
Output Jack tip - same volume as when bypassed.
this sounds like a bypass wiring issue, seems improbably if it was working though.
What are the resistances measured from input jack tip to Gnd, V+, and Vref? ..like something is shunting input to a DC reference.