Ibanez/Maxon older AD9 model issue

leeinthesprings

leeinthesprings

Member
I recently bought some old AD9 pedals (two Ibanez and one Maxon) because I like their tone.

I noticed on two of the pedals that the "protection" diode had become black on the leads. One of the pedals even had some damage to the circuit board from a capacitor... not sure if it was related.

The "protection" diode is a W03C. After seeing some Ebay ads with other AD9's I started to notice this similar issue of the W03C diode turning black. Seems like it is a very common issue. One guys pedal for sale had a really pronounced burn mark where the diode was (it had been replaced).

Has anyone ever heard of this issue with the AD9's?

What could be the issue with the W03C diode that they used? Which diode should I replace it with to possible fix the issue? I replaced one with a 1n4001. Is that a good option?

Any info/help would be much appreciated!

Thanks, Lee
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Might it be some kind of black coating added at the factory? I seem to remember opening up an old Ibanez/Maxon pedal and the resistors had all been painted pale green for some strange reason. I can't imagine diodes getting hot enough to discolour in a pedal. What sort of current would be needed to do that? More than is present in a pedal surely? And why would heat turn them black? This is all a bit odd.
 
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Could be from being hooked up to the wrong PSU? There was a point in time where everyone tried running tube screamers at 18V. I'm sure some genius guitarists tried running all their pedals at 18V with a 1 amp PSU borrowed from their dad's fax machine or something.
The burns marks on the one are probably from a repair with the wrong equipment--think plumbing soldering iron and plumbers flux.
The W03B was rated for 50V at 1 amp. The only way that gets heated up in circuit is improper power/polarity.
 
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