Turning on head accidentally without speaker attached question

Old Punker

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First of all, sorry if there is already similar topic in the forum :)

My question is, today I accidentally turned on my Marshall Silver Jubilee head for approximately 2 minutes (maybe less) without speaker attached to head. As soon as I noticed I shut it off, afterwards I reconnected everything and amp plays as before.

Situation was like this: Head turned on standby, no speaker attached to head, all pots on 0, no guitar attached. Could that possibly do any damage?

I ve heard people burn their amps while speaker is not connected when they try to play guitar and they crank volume up a bit.
Also I ve read that if amp is is standby and no guitar is connected, it could be turned on like that 100 years and amp won't get damaged..

Also I found this online, is this true statement?

"Most tube amps have shorting type speaker jacks to prevent flyback voltage in case you forget to plug in a speaker. But, if you plug a cable into the amp and not plug the other end of the cable into a speaker, then you have an open circuit that can cause flyback if the amp is played loud enough to generate the flyback. But what's "loud enough" to cause flyback damage? Amps aren't created equal so it would be difficult to say. However, there's a misconception that just turning a tube amp on with no load will damage it. With no input signal, flyback can't be generated...so an amp with no load and no input signal will sit there and do nothing for 100 years if the tubes last that long. It's only when there's enough signal from the amp (or it's in self oscillation) that flyback can be generated with no load. But, again, most tube amps have shorting speaker jacks that prevent flyback from occurring even with signal into the amp and the volume turned up."

Thank you all in advance, appreciate your answers, especially if they are explained from technical and electrical perspective since I am interested to know more.

As others have stated, you definitely did NOT cause any damage to your amp doing what you described. STANDBY = SAFE

As @EADGBE said - ALWAYS do a walk around before powering up your amp. I won't even plug an amp into the power receptacle until I'm sure a speaker cab is connected.

And please don't rely on shorting jacks, even if you're pretty sure an amp has them.

:cheers:
 

Saberslash

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Yu
As others have stated, you definitely did NOT cause any damage to your amp doing what you described. STANDBY = SAFE

As @EADGBE said - ALWAYS do a walk around before powering up your amp. I won't even plug an amp into the power receptacle until I'm sure a speaker cab is connected.

And please don't rely on shorting jacks, even if you're pretty sure an amp has them.

:cheers:
Yup, will be more careful next time.
But looks like standby saved my ass and my amp this time :D
Hehe
 

El Gringo

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As others have stated, you definitely did NOT cause any damage to your amp doing what you described. STANDBY = SAFE

As @EADGBE said - ALWAYS do a walk around before powering up your amp. I won't even plug an amp into the power receptacle until I'm sure a speaker cab is connected.

And please don't rely on shorting jacks, even if you're pretty sure an amp has them.

:cheers:
Very good advice . I always unplug from the electric outlet everything when I power down . I have both of my 2555X's going into a strip and plug that in first then connect the pedals that I will be using and then hit the power and let that have a few minutes and then I hit the standby and start playing . At the end hit the standby again , power down the pedals , then turn the amps off and then unplug the amps from the strip . As I will not chance leaving the 2555X's plugged in and risk some kind of spike and God forbid with a power spike fry something as these amps cost to much to be reckless and careless with them . I just feel more comfortable this way , pain in the neck but peace of mind is better than the alternative !
 

El Gringo

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As others have stated, you definitely did NOT cause any damage to your amp doing what you described. STANDBY = SAFE

As @EADGBE said - ALWAYS do a walk around before powering up your amp. I won't even plug an amp into the power receptacle until I'm sure a speaker cab is connected.

And please don't rely on shorting jacks, even if you're pretty sure an amp has them.

:cheers:
This is going to sound dumb so I will apologize in advance but what are the shorting jacks ?
 

SkyMonkey

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I have Valvestate VS65R (SS/hybrid) that I was changing the tube with the chassis pulled.
I switched it on to see if the tube glowed OK, but the speaker wasn't plugged in.
There was a whisp of smoke from somwhere on the circuit board and a nasty smell.
I switched it off straight away and shat myself.
It still worked once everything was reconnected, so I got away with it.

But, if an SS amp can suffer from no load with no signal, it can't be a general rule for all amps.

Just don't do it! (Sorry NIKE)
 
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Old Punker

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Very good advice . I always unplug from the electric outlet everything when I power down . I have both of my 2555X's going into a strip and plug that in first then connect the pedals that I will be using and then hit the power and let that have a few minutes and then I hit the standby and start playing . At the end hit the standby again , power down the pedals , then turn the amps off and then unplug the amps from the strip . As I will not chance leaving the 2555X's plugged in and risk some kind of spike and God forbid with a power spike fry something as these amps cost to much to be reckless and careless with them . I just feel more comfortable this way , pain in the neck but peace of mind is better than the alternative !

:agreed:

I do the same thing. All the gear in my music room is supplied by a single high capacity electric power conditioner which has surge suppression, ground fault detection, voltage regulation, and noise suppression. After I'm finished playing for the day I just pull one plug from the outlet and I know that everything is disconnected. You mentioned a power spike and this is indeed a valid concern. A number of years ago my father in law had a large spike run through his house during a heavy thunderstorm. Almost every electrical appliance and small device he had plugged into an electrical outlet was destroyed, even the ones that were shut off. Luckily he had a good insurance policy!
 

Old Punker

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This is going to sound dumb so I will apologize in advance but what are the shorting jacks ?

Hi @El Gringo, not dumb at all. I'm not a technician but AFAIK I've mostly seen these used on the inputs to the amp such that when nothing is plugged in, the input automatically goes to ground, so that the amp output will be zero. I believe this is done to reduce noises when plugging/unplugging guitars.

As for the speaker output shorting jack, this was discussed in another thread,

https://www.marshallforum.com/threads/shunted-speaker-output-jack-question.116954/

So it's a form of protection against open circuits when someone forgets to plug in a speaker, or gets disconnected while in use. I've also heard of some guys doing a slight mod to this by adding a fairly high wattage (5W) resistor which acts as a load, instead of having the OT short to ground.

The thing is, no one should rely on having this feature built into their amp (it's hard to know for sure unless you open up the amp and look), and it's not something you should rely on.
:cheers:
 
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Old Punker

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I have Valvestate VS65R (SS/hybrid) that I was changing the tube with the chassis pulled.
I switched it on to see if the tube glowed OK, but the speaker wasn't plugged in.
There was a whisp of smoke from somwhere on the circuit board and a nasty smell.
I switched it off straight away and shat myself.
It still worked once everything was reconnected, so I got away with it.

But, if an SS amp can suffer from no load with no signal, it can't be a general rule for all amps.

Just don't do it! (Sorry NIKE)

Yeah, it sucks when the magic smoke leaves a component! :wow:
 

Ken Ops

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I just leave everything connected, except a guitar of course, no matter what. So whatever happens, the amp by rights won’t do its best impression of the death star.

Plus, got relatively stable and protected power going to all the things, etc. Yeah, I play it safe.
 

PelliX

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But, if an SS amp can suffer from no load with no signal, it can't be a general rule for all amps.

There are (or mainly were, past tense) SS amps that would suffer without a load. These designs are not often encountered anymore, even in guitar amps. The circuitry required to make a relatively non-load dependant SS output or even integrate an auto-shut off (generally seen in SS hi-fi amplifiers) is so cheap and easy to implement, there's no real advantage in not having it.

Also, without a speaker connected, you don't know that there was no signal - oscillation will often constitute a fair amount of signal, for example. Or hum from a missing ground connection, etc.

The rule of thumb here is have a load or keep it on standby if it's a valve amp. Easy, right. :thumb:
 

Jethro Rocker

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There are (or mainly were, past tense) SS amps that would suffer without a load. These designs are not often encountered anymore, even in guitar amps. The circuitry required to make a relatively non-load dependant SS output or even integrate an auto-shut off (generally seen in SS hi-fi amplifiers) is so cheap and easy to implement, there's no real advantage in not having it.

Also, without a speaker connected, you don't know that there was no signal - oscillation will often constitute a fair amount of signal, for example. Or hum from a missing ground connection, etc.

The rule of thumb here is have a load or keep it on standby if it's a valve amp. Easy, right. :thumb:
Yep. That's what I have seen and a VS65R is a SS power section. I still think something else caused the smoke or it would be dead. I have killed output reansistors aay back jn the past from high level but too low an impedance. No smoke but transistor death.
No load on SS is the same as infinite load for transistor. It should be totally fine for an amp of that age.
Since the V65 has no output jack the only way to unplug speaker is from speaker end. Perhaps it shorted.?
 

SkyMonkey

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Since the V65 has no output jack the only way to unplug speaker is from speaker end. Perhaps it shorted.?
:hmm: Possible. I couldn't see the spade terminals from where I was sat.
But not a theory I am willing to experiment with.

There was another guy on the MF recently who said a similar thing happened to his VS100R, so maybe a design flaw too.

:shrug:
 

PelliX

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Yep. That's what I have seen and a VS65R is a SS power section. I still think something else caused the smoke or it would be dead. I have killed output reansistors aay back jn the past from high level but too low an impedance. No smoke but transistor death.
No load on SS is the same as infinite load for transistor. It should be totally fine for an amp of that age.
Since the V65 has no output jack the only way to unplug speaker is from speaker end. Perhaps it shorted.?

My guess would be that it was something else, too.

Generally, you can tell (visually) which component smoked. An output transistor seems more likely than a resistor in such an amp, but... :shrug:
 

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