Phase 90 "Ticking"

[zombiwoof]

A while back I did the Script mods to my early Dunlop Phase 90, it sounds great now, but I just noticed that when it's engaged there is a ticking sound you can hear when you stop playing, it changes speed when you turn the pot.  What could be causing this?  This is an older pedal, is some component going out?  Any ideas?

Al

[zombiwoof]

Just wanted to bump this up, doesn't anyone have an idea what could cause this ticking sound?  I know a lot of you guys have more knowledge than I do on this kind of stuff.

Al

[flo]

Please first try a search on this forum for "LFO tick" or "deticking" or something and get reading. 
I'll get you started with these:
http://www.diystompboxes.com/smfforum/index.php?topic=61250.msg480708#msg480708
http://www.diystompboxes.com/smfforum/index.php?topic=69638.msg559774#msg559774

[zombiwoof]

I read through most of the stuff in the search, and most of these problems were with new builds, mine is a stock Dunlop that I did the standard Script mods to.  The funny thing is, I never noticed the ticking before. after I did the mod, maybe it was just accented by the other pedals I hooked it up to recently.  A couple of guys said the ticking went away after removing R28, but in my case it started after I did that (and the other substitutions).  I guess it's a common problem, and most of what I was seeing in the search threads is beyond my knowledge, so I guess there is no easy fix for this.  Thanks anyway.

Al

[flo]

Can you test that when you put that resistor back, the ticking is gone again?
Some people advice to change only one component at a time and then test. This structured way of modding could have alerted you to exactly which change led to the ticking. Am sorry you are learning it the hard way...

[zombiwoof]

I did all of the basic Script conversions, not just R28, and it sounded fine after I did them.  I didn't use the pedal for a couple of months, plugged it in with a couple of others, and heard the ticking.  Really weird.

Al

[flo]

So when you use it on its own powered by a full battery, do you hear it ticking?

[zombiwoof]

Didn't check the battery, I'll try what you suggest and see what happens.

Thanks,
Al

[R O Tiree]

What else did you change apart from R28, C11 and C12 (the usual suspects)?

The ticking comes from the square-wave oscillator in the LFO causing the opamp's output to slam up and down to the voltage rails. The sudden current draw as it changes direction causes a voltage sag on the +9V rail of only a couple of mV, but it's enough to be perceived as a tiny ticking noise.

The way I solved this one was to replace the 470k resistor between pins 5 and 7 of the TL062 with a 1M resistor (R21, I think). This "relaxes" the oscillator, so it doesn't shoot up and down so quickly, reducing the instantaneous current draw when the oscillator changes state and eliminating the ticking.

[zombiwoof]

I did all the stuff listed on the bottom left of this page, under heading "script mods":

http://www.aronnelson.com/gallery/main.php/v/Schematics-etc/MXR_Phase_90_to_Script.gif.html?g2_imageViewsIndex=1

If the ticking still is heard after I replace the battery, I'll try your suggestion.

Thanks,
Al

[flo]

Using a low power opamp for U1 also helps like a TL062 or LM358.

[m_charles]

I had/have this problem with an old ph1-r and an arion sch-1. I haven't done it yet, but the advice I was given was before doing anything, replace all the electrolytics. Supposedly it "works every time."

[flo]

Old elco's go bad so only replace them when they are like more than 10 years old or so preferably first measure the capacitance.

[zombiwoof]

This is one of the older Dunlops, the ones that are built just like the original MXR's, so that is a possibility.

Al

[cpm]

i got into the ticking issue, on a new build. It was solved placing a 100 uF cap across the rails on the LFO opamp, strictly close to the pins

[oskar]

Using a lower power IC for the LFO helps to lower ticking. But the ticking shouldn't be there at all...
This thread might give a hint ( I don't mean any of my posts in it...     )
http://www.diystompboxes.com/smfforum/index.php?topic=72953.0