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Old 07-16-2013, 02:51 PM   #1
joner.jones
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Question How long do tube amps retain dangerous voltages?

Hello, I'm about to replace the valve in my VOX VT30 amp, which seems like a fairly simple process, but after reading up about it I've read that tube amps retain 'lethal' voltages for some time, which has me worried

Is there a usual amount of time that these voltages are retained? I've had my amp switched off for over two weeks now.

Also, can these electric shocks come from touching any conductive surface from inside the amp, or are there specific parts that are always a no-go and some parts that are fine?

All other forum posts I could find on the subject reach a - 'just take it to a professional' conclusion, but I'm looking to get educated on this too to avoid any accidents in the future.

Thanks
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Old 07-16-2013, 03:19 PM   #2
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You have nothing to fear if your amp is plugged off for more than a couple of minutes (right when you unplug it theoretically, but let's wait two inutes just in case).

Again, just in case wear rubber slipper.

Though, I'm not 100% sure about this so I'll feel a bit better if you waited for someone complitely sure to answer you before trying.
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Old 07-16-2013, 03:21 PM   #3
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You realise that isn't actually a tube amp? It's a modeller with a tube in it. I doubt changing the tube will have any effect.
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Old 07-16-2013, 03:23 PM   #4
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Quote:
Originally Posted by joner.jones
I've read that tube amps retain 'lethal' voltages for some time, which has me worried

Is there a usual amount of time that these voltages are retained? I've had my amp switched off for over two weeks now.

Also, can these electric shocks come from touching any conductive surface from inside the amp, or are there specific parts that are always a no-go and some parts that are fine?

All other forum posts I could find on the subject reach a - 'just take it to a professional' conclusion, but I'm looking to get educated on this too to avoid any accidents in the future.

Thanks


the components you are worried about are the capacitors (i think it's the filter caps in particular), big cylinder looking things. they'll hold a charge for quite some time. best not to risk assuming they are not charged, standard practice is that you ground them out.



you should probably learn some general amp and electronics knowledge before poking around a tube amp.
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Old 07-16-2013, 03:40 PM   #5
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thanks for the replies, Gary i realise that but i'm changing the valve as my amp had suddenly stopped producing sound from the speaker, and after much research (and some replies i had recieved on another forum post here) - i have reason to believe the problem lies with a burnt out valve in the output stage, so just replacing it to see if this fixes the problem. I'm sure i can replace it while avoiding any capacitors, but this stuff is good to know, thanks guys! very grateful for the help.
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Old 07-16-2013, 04:07 PM   #6
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There is no tube in the output stage
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Old 07-16-2013, 04:18 PM   #7
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Quote:
Originally Posted by JELIFISH19
There is no tube in the output stage


The ECC83 in the Valvetronix amps is in the output stage.

It doesn't do much, but it's definitely in the power section.
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Old 07-16-2013, 04:28 PM   #8
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To answer your question, you will not get shocked from changing a tube. There are no voltages present in that area when it's unplugged. The only thing you would have to worry about is if you opened it up and touched one of those big capacitors. You're going to be fine.
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Old 07-16-2013, 04:45 PM   #9
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Tube amps can retain lethal voltages for quite some time, depending on design.

Fortunately for you, yours isn't a tube amp, it's a SS amp with a tube...

Change it, you'll be fine.
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Old 07-16-2013, 04:48 PM   #10
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Quote:
Originally Posted by joner.jones
thanks for the replies, Gary i realise that but i'm changing the valve as my amp had suddenly stopped producing sound from the speaker, and after much research (and some replies i had recieved on another forum post here) - i have reason to believe the problem lies with a burnt out valve in the output stage, so just replacing it to see if this fixes the problem. I'm sure i can replace it while avoiding any capacitors, but this stuff is good to know, thanks guys! very grateful for the help.

Sounds like you've got the right expectations & doing it for the right reason - just checking
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Last edited by GaryBillington : 07-16-2013 at 05:06 PM.
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Old 07-16-2013, 04:58 PM   #11
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I think you're charging a 12ax7 preamp tube in a hybrid amp, nothing to fear.
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