Anyone tried this?

mightymike · Post by **mightymike** » Sun Jan 16, 2005 6:08 am

I was browsing Hoffman's site and stumbled on an article about draining fliter caps.
It suggested pulling the plug out of the wall with the amp on and your guitar pluged in. Then strumming some cords and listening till the sound as it dies down. Then according to acticle the caps would safely be drained down to a level that won't hurt you, but not all the way.

I was just wondering if this method it hard on the equipment? If so, would turning off the plug via wall switch, playing till the sound dies, then pulling the plug be any better?

And yes, I already know about jumping pin1 of V1 to chassis ground. I was thinking of trying Hoffman's suggestion, and then doing the jumper method. This way if you slip and touch something (it can happen) when cliping the jumper, the shock would be less severe.

Does this sound like a good proceedure?

tooloud · Post by **tooloud** » Sun Jan 16, 2005 1:15 pm

you will get about the same thing by turning the power switch off and strumming the strings till no sound.......

Eoin · Post by **Eoin** » Sun Jan 16, 2005 2:50 pm

If you unplug it, where is it discharging to?

npomares · Post by **npomares** » Sun Jan 16, 2005 8:55 pm

turn amp and standby off.unplug the amp from the electrical outlet, make sure speakers are still connected then turn power and standby on and strum the guitar until you do not hear any more sound check caps with a meter any way just to be sure. its a quick way to safe way to discharge the caps through a load which is the speaker

Eoin · Post by **Eoin** » Mon Jan 17, 2005 6:54 am

Makes sense. But why does it have to be unplugged to work?

Guest · Post by **Guest** » Mon Jan 17, 2005 4:44 pm

I'm sure you had the power cut while strumming a chord and noticed how the sound doesn't cut immediatly but rather fades and fizzles out. That's because it takes a few seconds for the BIG Caps to discharge. They are used to smooth out the ripple DC that comes off the rectifier bridge. The Diodes only let current flow in one direction and convert the AC to pulsation DC. Each pulse charges the filter cap which is almost like a battery, in between pulses. the Caps release that charge. The larger the cap the slower the release It takes a few caps to get the DC all the way smooth.

Here's a diagram of how this conversion would look through a scope.

mightymike · Post by **mightymike** » Mon Jan 17, 2005 4:45 pm

That was me. Forgot to log in.

Eoin · Post by **Eoin** » Mon Jan 17, 2005 7:18 pm

Indeed. But why does it have to be unplugged to work?

Guest · Post by **Guest** » Tue Jan 18, 2005 6:00 am

It doesn't have to be, it's just an extra safety precaution.

Eoin · Post by **Eoin** » Wed Jan 19, 2005 8:10 am

Hmm, in what way is it safer to discharge the amp with the earth lifted? It would seem to make more sense to me to leave it plugged in until you're opening it.

mightymike · Post by **mightymike** » Thu Jan 20, 2005 6:09 am

Eoin wrote:Hmm, in what way is it safer to discharge the amp with the earth lifted? It would seem to make more sense to me to leave it plugged in until you're opening it.

I guess the reasoning behind it is that you're already draining about 90 percent by doing the "Pull Plug Method". Sure it's not going to the earth ground, but it's being dissapaited by the load while you strum. You can hear it. It's supposedly a quick way to have your amp discharged down to a safe level before even opening it. If you want the best of both world I guess you could have the amp pluged into a wall plug that is on a switch, flip the switch while playing. I think it sounds like a good idea as long as it doesn't hurt anything/anyone. It just just seems scary. I imagine poping sounds when doing this.

For me personally, ,with one hand in my pocket. , I check the filters with my Meltimeter If I want to see if they're drained.

I was just curious if anyone tried this method.

It looks like it's not too popular around here, so I don't think I'll be trying it anytime soon.