XO Stereo Clone Theory issues

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clone_theory
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Post by clone_theory »

Hello,

I have one of the newer stereo Clone Theory pedals from Electro Harmonix. This was my favorite pedal until I messed with the internal trim pot, thinking that it would lower the volume boost :slap: Now it doesn't chorus, or it does for a few seconds and then sound like a bomb dropped and explodes and then... no more effect.

I don't have a schematic, but I was wondering if anyone has worked on one of these before? I was just wondering what I should be measuring to make sure that I adjust the trim pot correctly.

Any help is much appreciated.

Thank you!!

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Fender3D
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Post by Fender3D »

I don't know how much different is the new CT respect the older...
but if it has a BBD chip, then the trimmer is the bias setting.

It should be set for a symmetrical clipping:
apply a sine waveform then set trimmer for a symmetrical clipping.

Otherwise post some pics so we can guess about schematic...

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Post by clone_theory »

Thanks for the response, here are some pictures!

Image

Image

Image

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Post by Fender3D »

That's indeed a bias trim.

grab an o-scope and do what's on my 2nd post...

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Post by clone_theory »

Awesome, I think we have an o-scope at work, so I will try and do this.

Thanks!

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Post by chongwui »

Fender3D wrote: 25 Nov 2015, 17:05 I don't know how much different is the new CT respect the older...
but if it has a BBD chip, then the trimmer is the bias setting.

It should be set for a symmetrical clipping:
apply a sine waveform then set trimmer for a symmetrical clipping.

Otherwise post some pics so we can guess about schematic...
Hi, sorry for reviving an old thread. Where should I measure for the symmetrical clipping? Thanks.

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Post by Fender3D »

If you can locate the first LPF output after BBD you' ll get the best signal to "see" on scope...
Otherwise you should check at BBD's output pins (7-8 for MNxxxx)

Apply ~200Hz signal at input, raise it until you get clipping and set trimmer for a simmetrical clipping, raising and lowering signal applied will help ;)

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Post by wui223 »

Thanks for the tips. I pumped in 200Hz to input jack, measured pin 7 & 8 of MN3007. I couldn't see a sine wave on my scope, it looks like noise. I suspect the culprit is CD4047.

Question: How do I measure the clock signal output from the CD4047?

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Post by Fender3D »

Oscilloscope or DVM with frequency counter

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Post by kiltro »

wui223 wrote: 02 Mar 2021, 03:14 Thanks for the tips. I pumped in 200Hz to input jack, measured pin 7 & 8 of MN3007. I couldn't see a sine wave on my scope, it looks like noise. I suspect the culprit is CD4047.

Question: How do I measure the clock signal output from the CD4047?
Hello have you solved your problem?

I have a one with issues too... but I think it's different issue than yours (I'll post a video later).

First of all, how did you take it apart? It seems impossible to me without desoldering pots and switch (maybe I'm missing something though :oops: )

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Post by wui223 »

kiltro wrote: 19 Sep 2022, 10:25
wui223 wrote: 02 Mar 2021, 03:14 Thanks for the tips. I pumped in 200Hz to input jack, measured pin 7 & 8 of MN3007. I couldn't see a sine wave on my scope, it looks like noise. I suspect the culprit is CD4047.

Question: How do I measure the clock signal output from the CD4047?
Hello have you solved your problem?

I have a one with issues too... but I think it's different issue than yours (I'll post a video later).

First of all, how did you take it apart? It seems impossible to me without desoldering pots and switch (maybe I'm missing something though :oops: )
Hi kiltro. My pedal is still not repaired. I was not able to drill down to the exact root cause.

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Post by Fender3D »

hi wui, in my reply above, I assumed you messed with trimmer...
What's the issue with it?

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Post by kiltro »

I'll post here and eventually create another topic if you think is better.

This is a brief video of the issue I'm having with my pedal.



Obviously there is some pot cleaning to do, but what about the other weird sounds (the one at the start and the one at the end of the video)?
I guess is due to auto-oscillation? How should I go about solving it?

Thanks

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Post by Fender3D »

what about the other weird sounds (the one at the start and the one at the end of the video)
It looks related with power supply noise to me... the oscillation looks like a power supply loss in clock generator
it's really strange rate pot can make those heavy scratches.

Sure there's no cold solder or cracked track?

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Post by kiltro »

Fender3D wrote: 06 Oct 2022, 16:48
what about the other weird sounds (the one at the start and the one at the end of the video)
It looks related with power supply noise to me... the oscillation looks like a power supply loss in clock generator
it's really strange rate pot can make those heavy scratches.

Sure there's no cold solder or cracked track?
I've cleaned the pots and the scratches are gone.

Oscillation still happening though.

Power supply? Can it simply be the battery? :roll:

I dont see any cracked tracks but I'm not sure about cold solders

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Post by Fender3D »

You can hear that noise when there's loss of power supply in chorus or flanger usually, that's why I thought about issues in tracks or cold solders.
If you have DMM with max/min function, you can check supply at VCO, the clock chip.
BTW, it occurs in particular circumstances? Is it repeatable?

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Post by kiltro »

Fender3D wrote: 10 Oct 2022, 17:17 If you have DMM with max/min function, you can check supply at VCO, the clock chip.
My DMM has a peak button, but unfortunately it detects only max voltage, not min.
I've an oscope but I dont think there is something like that :hmmm:
Fender3D wrote: 10 Oct 2022, 17:17 BTW, it occurs in particular circumstances? Is it repeatable?
Well as far as I'm noticing...


clone-theory-1.mp3
(316.89 KiB) Downloaded 48 times
this one happens only with "chorus 1" and "chorus 2" selected
and only with rate knob in the range of min to 11 o'clock


clone-theory-2.mp3
(440.22 KiB) Downloaded 50 times
This one happens with range at max when not playing. Almost at random, or at least I'm not able to repeat it every time I try.
Also after the final "pop" the pedal exit chorus, after that if I play I get the bass sound without effect. I have to move the range pot to re-engage the effect

I'm also noticing that I get a subtle hum when the effect is on and if I touch the body of the jack that goes to the amp the hum is somehow reduced

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Post by wui223 »

Fender3D wrote: 05 Oct 2022, 19:30 hi wui, in my reply above, I assumed you messed with trimmer...
What's the issue with it?
Hi Fender3D. I presume the clock output from MN3007 at pin 7 & 8 is a sine wave? This is the 1st time I deal with chorus pedal. How about the clock driver IC (CD4047), what should I expect to see on pin 10 and 11?

Thanks in advance for your time :)

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Post by Fender3D »

@ MN's out pins you got the same signal injected at pin 3 altough delayed and "chopped".
@ 4047's pins 10-11 you got clock, it should be a square wave. When it suddenly drops below ultrasonic frequencies, you can hear the noise recorded in mp3 n°2

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Post by kiltro »

Edit: I guess I've used wrong datasheet for MN3007

Is this the right one?
IMG_20221013_174226.jpg
IMG_20221013_174226.jpg (31.54 KiB) Viewed 1111 times

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