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Thread: Locate the "raw bias supply" Peavey 6505

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    Locate the "raw bias supply" Peavey 6505

    I need to locate the "raw bias supply" in order to install a power scaling kit.

    ""Raw" bias is the value of the supply at the first filter cap and prior to regulation. This voltage should be fairly constant regardless of the loading, or not, of a bias-set network."

    I attach a small part of the schematics.
    Click image for larger version. 

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    At what point (A,B,C,D,E or F) should i solder the connection?

    Should i cut any cables (except for the point at "BIAS" because the installation provide a new bias supply)

    Please do not answer unless you are sure where it is!

    Edde

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    The first filter cap is C43.This is right after the half-wave rectifier diode, about as raw as you can get.That would make "C" the point you're looking for.

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    Thanks a lot! I finally start to understand the filters and stuff. Btw, can a capacitor be damaged if i make a short circuit with a cable?

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    In theory, yes. Without any specifics it is hard to tell if anything was damaged.
    I would strongly suggest you look at a current thread regarding this subject running in the general Guitar Amps forum.Or search for " installed an electrolytic".

    If there is *any* question, replace it. Caps are cheap.......................

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    When I was a relative novice working on a hi-fi rack mount unit with huuuuuge (10000uf+) capacitor arrays, I shorted it to the case to discharge it... It actually blew (disintegrated?) a small chunk out of the couple mm thick aluminium case, along with a noise that resembled a gunshot. A capacitors discharge rate is only really limited by it's ESR and whatever it's discharging into. I suppose you would melt the leads or heat up the internals enough to damage it at some point.

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    Quote Originally Posted by exclamationmark View Post
    When I was a relative novice working on a hi-fi rack mount unit with huuuuuge (10000uf+) capacitor arrays, I shorted it to the case to discharge it... It actually blew (disintegrated?) a small chunk out of the couple mm thick aluminium case, along with a noise that resembled a gunshot. A capacitors discharge rate is only really limited by it's ESR and whatever it's discharging into. I suppose you would melt the leads or heat up the internals enough to damage it at some point.
    Back in the late 1970s when I was attending tech school one of the guys in my class figured that a screwdriver blade would be far more expeditious than a discharge probe to discharge this big blue Sprague cap - the ones with the screw terminals. We spent about a half hour peeling him off the ceiling.

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