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Discussion Starter #1
Hey all. I've had my OD808 for over a year now, and something strange started happening. There is a digital noise coming from it, almost sounds like morse code and it is repetative.

This happens with both the battery and an adapter, and for both on/off modes while plugged in.

Any experience, ideas? I've never had a pedal do this before. Other pedals in my chain were not doing it, so it's not a room noise/EM noise thing.

cheers.
Gene
 

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Is it this one?

Or is it this one?

The upper is the original, which uses op-amps for the in/out buffers, while the lower one is the current reissue, using transistors for buffers.
If it's a more recent model, then something like a bad capacitor would be well down the list of potential problem sources. If it was an original, there is the outside chance that one or more of the 35 year-old caps have dried out. Although the noise you describe does not generally arise from dried out caps. Plus, the largest-value cap is 10uf.

And just to confirm, you get the noise when it is the only pedal in the chain?
 

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Discussion Starter #6
Is it this one?

And just to confirm, you get the noise when it is the only pedal in the chain?
I have the newer one, just a year old. I haven't had the chance to open it yet, since it uses those stupid little allen keys with the hole in them. FEK. couldn't just be allen or phillips.

yes, it also makes that noise when isolated, and with a battery. so it's not the adapter or another pedal.

I'll head to princess auto tomorrow, and look for some tools that will work.

p.s. thanks for the input
 

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So when you say a "Morse code" kind of noise, you mean a sort of "bee-bee-beeep-beeep-bee-beeeep" intermittent chirping, rather than any sort of noise like an AM radio tuned between stations?
 

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Discussion Starter #8
More like intermittent chirping, but it is not a solid tone per se, more like high frequency noise.

I got a tamper-proof torx bit, so I am taking it apart tonight to check some values... I found a schematic. Let’s see what’s going on in there
 

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Discussion Starter #11
Ok, nothing obviously wrong, nothing burnt or loose. All obvious stuff looks good, grounds, Vcc, etc.

Will check capacitors tomorrow.
 

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Discussion Starter #12
Ok, more info:

Noise is here :

It doesn’t appear when there is no input. Once a plug is inserted to input(i.e applying power) the noise happens while either disengaged (buffered bypass) or engaged through guts of the pedal.

The 100uF cap on power supply holds a steady 9V. No fluctuations I can see on the DMM. All the grounds seem good.

I found one schematic that looks close, but not exact. Right now I am suspecting the buffered input which I think is common to both modes.

Thoughts?
 

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Thanks for posting that. It will help pinning down the source.
If the pedal circuit is always on (as is true of all e-switched pedals), and the noise only occurs when something is inserted into the input jack to turn on the power, AND the noise occurs whether the power is external or battery, AND the 100uf cap seems fine, THEN our attention turns to D1, which is used as a wrong-polarity protection diode, going to ground. They can get fried when people plug in a supply with the wrong polarity.

The diagnostic test would be to desolder one end of that diode, so that it is effectively out of circuit. If I'm right, the noise should abate. Since it is not in the audio path at all, there is no requirement to find an exact replacement. It can be easily replaced with a 1N4001.

Fingers crossed.

EDIT: I should add that the diode is not required for the pedal to function. It is only there to assure the pedal keeps on working, and doesn't get damaged by plugging in the wrong type of adaptor or too high a voltage. So, as long as you apply battery or external power properly, lifting the diode won't wreck anything.
 

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Discussion Starter #15
THEN our attention turns to D1, which is used as a wrong-polarity protection diode, going to ground. .
Just to be sure, are you talking about the diode in parallel with the 100uF cap? Because that is labelled D5 on the board. D1 and D2 are connected to the op amp.
 

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Yes, the black one with the white stripe, not either of the two smaller orange glassy ones. I was looking at a different schematic, to confirm the diode went to ground and wasn't in series with V+, forgetting what the part was labelled on the actual board.

Thanks for noticing the error.
 

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Jeez that's a puzzler. I don't want to start suggesting to change this or that component, because I don't want you to risk damaging the board.

I'm going to cogitate a bit more. I'll refer a few of the expert minds I know to the video, and get their take on it. I'll be back.
 

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It is you’re WiFi/cell phone. Can’t recall which but try isolating those. Same thing happened to me a while back.

 

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Discussion Starter #20
It is you’re WiFi/cell phone. Can’t recall which but try isolating those. Same thing happened to me a while back.

It’s not my cell phone, i’m aware of that one. This is isolated to this specific pedal.

I’m thinking that it may be a noisy transistor.
 
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