Vox VT40+ giving shocks

[spleenharvester]

As title really. It's done it since as long as I can remember, it's been PAT tested and passed.

But when it is unplugged, if you touch two of the pins on the plug, you get a small shock. Doesn't seem to be long enough in duration for me to get the exact voltage on my multimeter. Not powerful enough to throw you around or anything.

Any ideas? Only reason I ask is that I've come to sell it. The thing would only get £100 used max anyway so it's not really worth taking to a tech.

Am I best off just selling it cheap as spares/repairs?

 

[trevorus]

Re: Vox VT40+ giving shocks

You mean, when you touch the AC cord after the amp has been plugged in? Is the power switch off? I would guess the capacitors are somehow still connected to the AC input and you are feeling their discharge. Easiest solution, stop touching the cord!

 

[Jocelyn]

Re: Vox VT40+ giving shocks

Let me get this correct. You use the amp. then switch it off then pull the plug from the outlet and touch the pins on the plug of the amp, you get a shock. This is can happen with any electric equipment. It is because the unit still has A charge stored in it which is not released yet. This is what I do and it works; after I switch of and unplug am\n electric appliance, I touch the pins to a wall, to earth it. It seems stupid but it works well.

 

[ItsaBass]

Re: Vox VT40+ giving shocks

Wow. I'm surprised Ampeg let them get away with that one.

 

[Adieu]

Re: Vox VT40+ giving shocks

Let me get this correct. You use the amp. then switch it off then pull the plug from the outlet and touch the pins on the plug of the amp, you get a shock. This is can happen with any electric equipment. It is because the unit still has A charge stored in it which is not released yet. This is what I do and it works; after I switch of and unplug am\n electric appliance, I touch the pins to a wall, to earth it. It seems stupid but it works well.

creepy! can any amps give you SERIOUS shocks like that??? cause I can't remember ever experiencing anything like this, but I also don't remember anyone (or any manufacturer!) warning me not to touch the pins of an unplugged electrical plug thingie either... so I never watched to make sure it doesn't touch my body or anything like that once it's been unplugged.

 

[GuitarStv]

Re: Vox VT40+ giving shocks

spleenharvester - Doc, you gotta help me, every time I stick this fork in my eye it hurts.
Doc - Don't stick the fork in your eye.
spleenharvester - Ooooooohhh . . .

 

[hydro]

Re: Vox VT40+ giving shocks

I've often heard that discharging capacitors by shorting across the ac plug using a screwdriver, etc. is recommended prior to working on computer gear, amps, electronics.

 

[uOpt]

Re: Vox VT40+ giving shocks

I've often heard that discharging capacitors by shorting across the ac plug using a screwdriver, etc. is recommended prior to working on computer gear, amps, electronics.

I don't think the capacitors should easy be able to reach the output plug even in an old-style non-switching power supply. They should sit behind the rectifier and not be able to make it back.

 

[hydro]

Re: Vox VT40+ giving shocks

I don't think the capacitors should easy be able to reach the output plug even in an old-style non-switching power supply. They should sit behind the rectifier and not be able to make it back.

It may be an old wives' tale. I've heard similar things about standby switches being switched to "on" with the power off, as a way to drain caps. Not sure if any of it is valid with more modern designs.

 

[uOpt]

Re: Vox VT40+ giving shocks

It may be an old wives' tale. I've heard similar things about standby switches being switched to "on" with the power off, as a way to drain caps. Not sure if any of it is valid with more modern designs.

Yes but that goes forward toward the amp, not backwards through the rectifier.

 

[Myaccount876]

Re: Vox VT40+ giving shocks

creepy! can any amps give you SERIOUS shocks like that??? cause I can't remember ever experiencing anything like this, but I also don't remember anyone (or any manufacturer!) warning me not to touch the pins of an unplugged electrical plug thingie either... so I never watched to make sure it doesn't touch my body or anything like that once it's been unplugged.

Its not like it is common practice to touch plug-pins right after they're pulled out. I don't think I've ever tried it to know honestly.

But amps (especially tube amps) have more than enough potential to shock you. Filter capacitors often hold a lethal charge and it is advisable to drain them first if you are working in that section of the amp.

Keith Relf, John Rostill, and Leslie Harvey all died of electrocution by music-related causes. Read this. Another thing to always be sure of is to NEVER neglect the 3rd grounding pin on any plug that has it. It really becomes natural selection at the point where someone thinks neglecting the ground pin is ever a good idea.

Also, don't stick your keys in the outlet.

 

[spleenharvester]

Re: Vox VT40+ giving shocks

I've never had ANY piece of electrical equipment give me a shock after use. I found this out just unplugging the amp after a gig, not exactly rubbing my face on it or anything. And I sure as hell wouldn't feel comfortable selling it without putting it in the listing. But cheers anyways.