Repairing power-fried pedals

[jakenold]

Something you CAN credit T-REX, is their color coded cables, supplied with their a little too pricey Fueltank power supply.

The 12V AC is red and is the only plug that fits into the 12V AC output - although the barreljack naturally fits into your of-the-shelf 9V DC pedal 

[bioroids]

  I had some trouble with 2.5mm vs 2.1mm incompatibility.
 

Absolutely! the worst thing is, a 2.1 and 2.5 plug have the same outer diameter, it's the diameter of the inner conductor that the measurement refers to. So you can put a 2.5 plug in a 2.1 socket, and the inner pin in the socket can intermittently  make contact - or not at all.

I have a bag of 100 2.5mm jacks laughing at me at the desk... what was I thinking?

Great post R.G.! I'm one of the few that use a series diode (1N5817, schottky) in their pedals (without problems so far)

Luck

Miguel

[dxm1]

There's actually a variant of the MOSFET protection that makes an active bridge out of MOSFETs. This was suggested to me a ways back, and it seems like a good idea. You can hook up a "rectifier bridge" out of two N and two P channel MOSFETs. This can be arranged so that both polarities of applied input voltage are rectified to the correct one. What makes this good is that instead of losing two series diode drops as you would with ordinary diodes, this arrangement could have a voltage loss of under 0.1V, maybe less. It was an expensive device back when TO-92 MOSFETs were $1.00, but now that they're nosing around $0.30, it's getting more practical.

RG, you've offered to post this circuit a few times, but I haven't seen it here.  I found an article on GEO about MOSFET protection which also mentions the 'bridge' circuit, but no schematic.  I realize it's been years, but if you still had the drawing handy...

[Dimitree]

would the transistors survive with reversed voltage?

[alparent]

Thanks for that R.G. Perfect timing.

A lady gave my brother a keyboard.

He pluged it in played a bit and took it home. When he got home pluged it in again and nothing!
He brought it to me.......and first thing I noticed is that the keybaord says 9v on it but the adaptor he had is 24v !!!
The polarity was ok but way over on the voltage. So I used one of my 9v adators.

I don't understand how it even worked with the 24v in the first place? 

Now I only get the power LED that comes on (but the power switch is at off!)
Nothing works on it, no sound, the switches do nothing, just that LED that comes on.

I guess something is fried in the power section.

[AdamCharlton]

I accidentally plugged an ac adapter into most of my pedals, but they still works. I'm using batteries right now until I get my voodoo lab power supply that I ordered. If they still work is there still a chance that I may have damaged them ?

[GibsonGM]

I accidentally plugged an ac adapter into most of my pedals, but they still works. I'm using batteries right now until I get my voodoo lab power supply that I ordered. If they still work is there still a chance that I may have damaged them ?

Got you on the other post you made, Adam!  Only way to know is to run them thru their paces - odds are that they DID get damaged, but be sure, first.

[EBK]

This has been very enlightening (referring mostly to OP).  Never thought electrolytics would be first to go.  Always thought they were fine as long as they looked fine, i.e., no leaking and no explosion.  . Now I know.

[yanyan]

For about 2-3 years i used a Roland ACR 9V adapter (that came with my Micro Cube) to power pedals: a Digitech Bad Monkey and a DOD YJM308. Then i learned the ACR adapters are unregulated. I made a reading of the voltage output and it was a whopping 15V. I stopped using the adapter and went back to batteries.

If there was any damage done, would it be noticeable? Perhaps a change in tone? The pedals work fine and sound the same as before - though keep in mind i might very well be in denial. Is it possible to damage the pedal just so that it would keep working yet sound different? Or would damage by over-voltage completely kill 1 or more components rendering the pedal useless?