Author Topic: Pedal works with battery but when connected at wall plug it blows a cap  (Read 2587 times)

rockaffe

I've build a Greg Fryer treble booster from Paul in the Lab and, when connected via battery snap, it works (as I said on another thread I have big hum, but ok, the pedal works).
I've then tried to box it and connect it via 9v adapter and... it doesn't work. As soon as I plug the adapter to the wall plug the C6 capacitor blows.
Could it be because of a bad adapter, (It's a universal one with many voltage selector), or could it be something else?
Thank you!

https://paulinthelab.blogspot.com/2013/03/greg-fryer-brian-may-treble-booster.html

bluebunny

Re: Pedal works with battery but when connected at wall plug it blows a cap
« Reply #1 on: November 16, 2018, 03:56:35 PM »
I think you might need to show us that PSU of yours. A great way to blow up an electrolytic cap is to reverse the voltage across it (aka. put it in backwards). Perhaps the battery didn't have the juice for a spectacular failure? A PSU certainly would. Or it might be something else...  :)  Pictures of your build would be good too.
« Last Edit: November 16, 2018, 04:18:26 PM by bluebunny »
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Ohm's Law - much like Coles Law, but with less cabbage...

rockaffe

Re: Pedal works with battery but when connected at wall plug it blows a cap
« Reply #2 on: November 16, 2018, 04:27:29 PM »
I think you might need to show us that PSU of yours. A great way to blow up an electrolytic cap is to reverse the voltage across it (aka. put it in backwards). Perhaps the battery didn't have the juice for a spectacular failure? A PSU certainly would. Or it might be something else...  :)  Pictures of your build would be good too.

Hi, thanks for your reply :)
Here is my PSU:



bluebunny

Re: Pedal works with battery but when connected at wall plug it blows a cap
« Reply #3 on: November 17, 2018, 04:16:09 PM »
Underside too? Sorry, I'm finding this difficult to view properly: my fault, not yours (on vacation, reading on my phone).  Perhaps someone else will be along shortly to put eyes on this too. I'm sure we'll get to the bottom of this!
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Ohm's Law - much like Coles Law, but with less cabbage...

rockaffe

Re: Pedal works with battery but when connected at wall plug it blows a cap
« Reply #4 on: November 17, 2018, 04:41:03 PM »
Underside too? Sorry, I'm finding this difficult to view properly: my fault, not yours (on vacation, reading on my phone).  Perhaps someone else will be along shortly to put eyes on this too. I'm sure we'll get to the bottom of this!

Problem solved. The pedal works with negative polarity and I've plugged it with positive :D Now it works, but the amount of hum is incredible...

bluebunny

Re: Pedal works with battery but when connected at wall plug it blows a cap
« Reply #5 on: November 18, 2018, 06:27:20 PM »
Reversed power - exploding caps - initiation complete.  ;D

Perhaps post a new thread in the main "Building your own stompbox" subforum and we'll get the hum sorted too.
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Ohm's Law - much like Coles Law, but with less cabbage...

rockaffe

Re: Pedal works with battery but when connected at wall plug it blows a cap
« Reply #6 on: November 21, 2018, 07:15:31 AM »
Reversed power - exploding caps - initiation complete.  ;D

Perhaps post a new thread in the main "Building your own stompbox" subforum and we'll get the hum sorted too.

Thank you! You're really kind!
In fact, I've breadborded the pedal and there is no hum, so I guess I've to improve my solder skills :D
A fun fact about the breadborded pedal: it works, but: if I turn the guitar volume to max some pickups don't send signal to the amp. I've to keep it at about 8/9 to have all the guitar working :D
I hate to be a noob!  :icon_mrgreen: