can amp be on standby while changing pre-amp tubes?

tommy

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Feb 8, 2002, 7:48:32 AM2/8/02

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I would like to know if the amp can be on standby when changing the
pre-amp tubes only. or will this damage the amp or tubes or both?

thanks

Chris Spraggins

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Feb 8, 2002, 8:46:18 AM2/8/02

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When an amp is on standby it normally feeds the heaters on the valves/tubes (all of them ,pre amp ,phase splitter and power stage ) this keeps them warmed up , when the main switch is thrown then the HT or high voltage is supplied to the anodes/plates of the valves/tubes .
I would never change a valve/tube without turning the amp off totally and unplugging , and allowing to cool ,if you don't you will probably damage the valve , the amp and yourself.

Steve Cowell

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Feb 8, 2002, 8:58:20 AM2/8/02

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On 8 Feb 2002 04:48:32 -0800, tommy...@hotmail.com (tommy) wrote:

>I would like to know if the amp can be on standby when changing the
>pre-amp tubes only. or will this damage the amp or tubes or both?

Hell, I change preamp tubes when the thing's on full, just turn
down the volume. You might get shocked, is all... standby
is fine. If you're comparing lots of preamp tubes, powering it
down and up is harder for the amp, anyway.
__
Steve
.

Mel Martin

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Feb 8, 2002, 1:43:04 PM2/8/02

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Not a good idea... the standby switch only cuts off the final tubes...
filament and screen and plate voltages are still present. It can cause
sparking and pitting of the tube base contacts, you can certainly burn
yourself, and if a tube breaks, you could electrocute yourself.

Robert M. Braught

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Feb 8, 2002, 5:53:28 PM2/8/02

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Hey I'll vote too!

FWIW not all 'standby' switch operations are the same- to answer you
question with authority, what amp are we talking about?

(i.e. Silvertone 'standby' leaves all voltages in place, but shorts the
grids of the output tubes together for no sound... most others
disconnect the high voltage -plate and screen- from *all* the tubes, but
leaves filament supply on...)

Ok I'm with Steve, and swap tubes on the fly ('full' power on, volume
down) *all the time*, but then again I can fix anything I blow up if I
slip (FWIW haven't had to for years, knock on wood), but what would I do
if I couldn't?...

I'd probably switch to standby, pull/reinstall the preamp tube, then
switch off standby...

(There are also a few amps out there, like the SVT, that *really* don't
want their preamp/driver tubes yanked full power on!)

Cheers,
-Robert
QTS
http://www.Braught.com

Mel Martin

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Feb 9, 2002, 4:25:51 PM2/9/02

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A lot of modern amps leave the preamp tubes fully powered up in standby...
handy if you use the line out... I'd still rather do it the safe way...
change the tubes with the amp unpowered... but hey... it's your amp!

"Robert M. Braught" <elec...@grapevine.net> wrote in message
news:3C6456E8...@grapevine.net...

Anders Vedel Bak

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Feb 9, 2002, 8:54:36 PM2/9/02

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But is this not what could lead to the much-talked-about
"cathode-stripping" - if you change tubes with full voltage, the tube will
not be properly heated before applying full voltage - or does that only goes
for output-tubes?
I always thought that the high voltage were disconnected with the standby
switch, therefore i have been changing preamptubes in that manner - but this
gives food for thought - have to see if my preamp still works on standby.

Regards,
Anders Bak

RoccaforteAmps

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Feb 10, 2002, 11:42:48 AM2/10/02

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You can change preamp tubes
with your amp on standby
all day long,
BUT I dont recomend getting
into this habit .
I do this when juggling tubes
for microphonics sometimes,
cant stand shuting the amp
down and waiting for it to come back.
Doug

Roccafartamps

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Feb 14, 2002, 7:03:05 PM2/14/02

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>I would like to know if the amp can be on standby when changing the
>pre-amp tubes

You can have the amp full on while replacing tubes. It helps isolate problems.
It you hear a pop when you pull it, you know that stage is working. Most
techs use this methed to troubleshoot.

RoccaforteAmps

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Feb 14, 2002, 7:28:33 PM2/14/02

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<<roccaFart wrote: You can have the amp full on while >replacing tubes. It

helps isolate problems.
>It you hear a pop when you pull it, you know that >stage is working. Most
>techs use this methed to troubleshoot.
>>

I did write this,
but I just forwarded to usenet.
RoccaforteAmps

Roccafartamps

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Feb 15, 2002, 1:50:39 PM2/15/02

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>I did write this,
>but I just forwarded to usenet.
>RoccaforteAmps
>

Why would you want to forward my post to usenet you weirdo?? Are you gay or
something? I'm not into that shit, so keep your distance.

FoilBoy's Foil

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Feb 18, 2002, 11:28:39 PM2/18/02

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FORGERY ALERT
-------------
The article below, supposedly from
roccaf...@aol.com (Roccafartamps),
is an attempt by an individual
(posting as RoccafartAmps or
something similar) to harass a
legitimate business, and AGA
contributor (RoccaforteAmps)
by using a similar posting name
and email address. Please ignore
all posts by
roccaf...@aol.com (Roccafartamps) and similar names, or
forward them including to
tosu...@aol.com.

>----------- Begin Forwarded Message -----------

FoilBoy's Foil

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Feb 18, 2002, 11:29:30 PM2/18/02

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FORGERY ALERT
-------------
The article below, supposedly from
roccaf...@aol.com (Roccafartamps),
is an attempt by an individual
(posting as RoccafartAmps or
something similar) to harass a
legitimate business, and AGA
contributor (RoccaforteAmps)
by using a similar posting name
and email address. Please ignore
all posts by
roccaf...@aol.com (Roccafartamps) and similar names, or
forward them including to
tosu...@aol.com.

>----------- Begin Forwarded Message -----------
>