2 Broken Pedals

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I picked up a few broken pedals pretty cheap thinking I could learn how to fix them by doing so...

First is a Fulldrive 2. The circuit board almost looks burnt by where the power comes in. There are two diodes going in opposite directions next to each other right where the power comes in (Fail safe for incorrect power?). Could it be someone cooked the two diodes (if thats what they do) with AC or high voltage?

Second is a Keeley modded Rat. The volume cuts in and out while playing, then when its picked up and re-adjusted it starts working again. It behaves like a bad cable does, but it's not my cables. Could it be a bad switch or jack?

Thanks guys!
-Tyler

[mth5044]

Probably easier to keep the two pedals in two different threads, but check out this debugging thread.

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

Pictures are also helpful of the Fulldrive, where it's burnt. Finally, if you have schematics or anything for posting, please do!

Make sure the jacks are tight on the Rat and the wires connecting to the boards and peripheral stuff is all secure and has nice solder joints.

[amptramp]

I suspect you are right about the Fulldrive.  Find the schematic or trace out that section and see what you would expect to be there.  It is common to put in a diode that is reverse biased under normal power but conducts when the polarity is wrong.  In this case, you have a contest between how much power the power supply can put out versus how much the diode can conduct without failing open.  (Failing short protects the circuit but requires the diode to be replaced.)

With the Rat, make sure the ground connections are made by wire and not just the chassis from the input ground to the output ground to the board ground.  Relying on the enclosure will cause the symptoms you have described.  Also check for breaks in the solder for the ground wiring that does exist.  Jack nuts backing off and permitting the wires to twist are among the most common faults.

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How do I add pictures to a post?

[Switchfooter]

Heres the circuit board for the RAT, could the rust be causing my issues?

[amptramp]

The brown glop surrounding the soldered connections is the resin flux from the solder.  It can be removed but it usually doesn`t matter.

[Switchfooter]

Ok, so now that that has been eliminated, does anyone else have any ideas what could be causing the issues with the rat? Maybe the switch?

[armdnrdy]

There are some very talented individuals that frequent this site but....
I haven't witnessed any circuit whisperers.
You must help us....help you.

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0