Roger Mayer Voodoo vibe troubleshooting

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Ang3lus
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Post by Ang3lus »

I've had this one for a while, was working perfectly but now i get low output and the effect drops volume when engaged, bypass works, the Chorus/Vib/Trem modes all work but the sound has a very loud bass thump to it.

I've attached a schematic i've found, I suspect the first Transistor because the LFOs all work and the leds behave normally, anything other i need to check just in case ?

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Ang3lus
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Post by Ang3lus »

Anyone?

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Ang3lus
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Post by Ang3lus »

Added a video, the Roger mayer company do not support units that are over 10 years old.. didnt even supply a schem/voltage chart etc, kind of annoying, thank god for people who trace circuits...

hope anyone has any idea on how to approach this ?

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Ang3lus
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Post by Ang3lus »

video
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mauman
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Post by mauman »

I think I'd start with an audio probe, looking for a fault in the section circled in red, maybe a failed transistor or bad connection. It seems like bypass/output buffer is fine, LFO is working, and vib/chorus/trem selection section is working. so those should be OK. Second choice would be the modulation section at bottom right.
Marked schematic
Marked schematic

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Ang3lus
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Post by Ang3lus »

Thanks, I will check this section today

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Ang3lus
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Post by Ang3lus »

Two things that I found
There's a really strong GNd loop hum in the pedal, don't know if it means anything

2. I injected a signal right after the first transistor and the signal was weak (also at the end of the modulation chain and signal was normal)
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mauman
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Post by mauman »

I think I'd replace the first transistor, then the second one.

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Post by Ang3lus »

Right on the money, it was the first transistor

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Post by BMS1971 »

I have a question about the output stage? Why so complicated? Wy did he added the PNP/NPN pair + a output stage?
Ben

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