Announcement

Collapse
No announcement yet.

Ibanez PT-9 Phaser Bias Adjustment

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • clarisso11
    replied
    I managed to reproduce the Lissajous pattern from the service manual, using the method provided by Helmholtz, all looking good now! A word of warning to everyone attempting this, the correct trim pot range to get it right is tiny, even the slightest adjustment will throw it off.

    Leave a comment:


  • clarisso11
    replied
    Originally posted by g1 View Post
    If the bias trim is not a sealed type, you should probably give it a shot of cleaner.
    Thanks! Definitely wouldn't hurt..

    Leave a comment:


  • g1
    replied
    Originally posted by clarisso11 View Post
    When I swapped out the broken component, I didn't get signal at first, but regained the effect when adjusting the bias trim pot a little
    If the bias trim is not a sealed type, you should probably give it a shot of cleaner.

    Leave a comment:


  • clarisso11
    replied
    Originally posted by Helmholtz View Post
    Do you really need to change bias adjustment?

    For adjusting by ear using a 400Hz or lower frequency square wave input signal might work.

    To display Lissajous figures with your scope you need to set it to x/y mode. First channel probe goes to input second channel to output.
    Oh, that makes sense! I'll try connecting to input and output.

    When I swapped out the broken component, I didn't get signal at first, but regained the effect when adjusting the bias trim pot a little; just wanted to make sure I adjust it correctly.

    Thanks everyone, that should be enough to sort it out!

    Leave a comment:


  • Helmholtz
    replied
    Do you really need to change bias adjustment?

    For adjusting by ear using a 400Hz or lower frequency square wave input signal might work.

    To display Lissajous figures with your scope you need to set it to x/y mode.
    First channel probe goes to input, second channel to output (I think, as not otherwise noted)
    It typically takes a while to find the best scope settings.
    Last edited by Helmholtz; 05-17-2021, 06:05 PM.

    Leave a comment:


  • clarisso11
    replied
    Originally posted by dmeek View Post
    I've never heard of using a scope to set the bias . I use a white noise input, listen to the output and set it by ear.
    I might give that a go (with input being looped guitar or something similar), until I figured out how to do it following the service manual. Thanks!

    Leave a comment:


  • dmeek
    replied
    I've never heard of using a scope to set the bias . I use a white noise input, listen to the output and set it by ear.

    Leave a comment:


  • clarisso11
    started a topic Ibanez PT-9 Phaser Bias Adjustment

    Ibanez PT-9 Phaser Bias Adjustment

    Hi everyone,

    I've been working on repairing a Ibanez PT-9 Phaser, and have already made a lot of progress, thanks to help from this forum!

    The pedal is back up and running again, but needs bias adjustment. I have done this in the past with simpler circuits, but have trouble making sense of the instructions in the service manual (attached).

    I have just gotten a dual channel oscilloscope, so I should be able to produce some lissajous patterns (I'm using my phone as a signal generator).
    My question is: Where exactly do I have to put the probes? I can't see that mentioned in the manual. Does it just go to the output jack?


    Ibanez_PT9_service_manual.pdf
Working...
X