PT was pretty warm but everything checked out....so much for all the dire warnings i have heard
amp abuse
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amp abuse
by nyazzip » Fri Jul 12, 2013 8:41 am
i just discovered i left one of my cheap little SE guitar amp on for the last 20 hours with no speaker load connected....
PT was pretty warm but everything checked out....so much for all the dire warnings i have heard
PT was pretty warm but everything checked out....so much for all the dire warnings i have heard
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nyazzip - KT88
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Re: amp abuse
by 20to20 » Fri Jul 12, 2013 11:23 am
nyazzip wrote:i just discovered i left one of my cheap little SE guitar amp on for the last 20 hours with no speaker load connected....
PT was pretty warm but everything checked out....so much for all the dire warnings i have heard
I think the problems occur when an amp is actually driven with test signals applied that take the outputs up with no load. If there is no signal there is no current other than the quiescent current. No high voltage spikes to deal with.
Headed for Tishomingo to sing in a can...
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20to20 - KT88
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Re: amp abuse
by DeathRex » Fri Jul 12, 2013 11:54 am
I've seen EL84s arc inside when the op transformer was unloaded. Luckily they survived.
At first I wanted to be a ET. Now I are one.
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Re: amp abuse
by Geek » Fri Jul 12, 2013 5:42 pm
SE guitar amps with no NFB shouldn't be a problem with no input unless it's inherently unstable and likes to oscillate.
It's the NFB + unloaded that causes real problems
It's the NFB + unloaded that causes real problems
-= Gregg =-
Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
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Geek - KT88
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Re: amp abuse
by nyazzip » Fri Jul 12, 2013 8:47 pm
yeah there was no input, so i was wondering if that may have saved me....
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nyazzip - KT88
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Re: amp abuse
by soundbrigade » Sat Jul 13, 2013 1:34 am
From my Priboi amp:
WARNING!
NOT RECOMMENDED POWERING UP WITH LOAD CONNECTED!
WARNING!
NOT RECOMMENDED POWERING UP WITH LOAD CONNECTED!
Magnus
"It is always more difficult to fight against faith than against knowledge."
"It is always more difficult to fight against faith than against knowledge."
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soundbrigade - KT88
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Re: amp abuse
by azazello » Sat Jul 13, 2013 10:55 am
Magnus<........"......with load disconnected!"
Projects: OTL 6AS7 Gen, Electric, SEs 2A3 RCA, 300B JJ, 6S4S, 4P1L, EL11 Telefunken, 6AS7 RCA, 6S33S, 6S41S, 6S19P, headphone ampl. OTL Loftin White 6AS7 RCA....SE E84L&E80CC Siemens&Tel-n.
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Re: amp abuse
by kt88pppamp » Sat Jul 13, 2013 11:05 pm
I had an incident with my KT88/KT90 PPP amps. I had them on the bench to check the bias and decided to hook up the function generator to perform another THD test with another 12AX7 driver. Well, here is what happened:
- I set the function generator to 20KHz full power and took the reading.
- When I set the generator to 1kHz, I heard a snap and smelled smoke. I looked at one of the tubes and I saw red plating.
- I powered down the amp and saw one of the 100 ohm screen stoppers was toasted.
I put in a new resistor and returned the amp to service. It is working fine now. What causes anomalies like this to occur? Was that abuse to jerk the frequency at full power at 20K down to 1K or a fault in the circuit? Should I be concerned about music at very high volumes doing something similar?
- I set the function generator to 20KHz full power and took the reading.
- When I set the generator to 1kHz, I heard a snap and smelled smoke. I looked at one of the tubes and I saw red plating.
- I powered down the amp and saw one of the 100 ohm screen stoppers was toasted.
I put in a new resistor and returned the amp to service. It is working fine now. What causes anomalies like this to occur? Was that abuse to jerk the frequency at full power at 20K down to 1K or a fault in the circuit? Should I be concerned about music at very high volumes doing something similar?
-Ice cream is irresistible.
-Spaghetti and salt is irinductable.
-Artichokes are ircapacitable.
-Spaghetti and salt is irinductable.
-Artichokes are ircapacitable.
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Re: amp abuse
by nyazzip » Sun Jul 14, 2013 12:07 am
Was that abuse to jerk the frequency at full power at 20K down to 1K
can't be- that is normal in many musical passages(approximately)
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nyazzip - KT88
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Re: amp abuse
by kt88pppamp » Sun Jul 14, 2013 12:33 am
I wonder what caused the screen stopper to fail? Faulty tube?
Last edited by kt88pppamp on Sun Jul 14, 2013 12:48 am, edited 1 time in total.
-Ice cream is irresistible.
-Spaghetti and salt is irinductable.
-Artichokes are ircapacitable.
-Spaghetti and salt is irinductable.
-Artichokes are ircapacitable.
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kt88pppamp - KT88
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Re: amp abuse
by Geek » Sun Jul 14, 2013 12:37 am
kt88pppamp wrote:I wonder what cause the smoke then?
No one heard Quackti's 'safe word' until it was too late
Sorry, couldn't resistor
-= Gregg =-
Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
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Geek - KT88
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