Vacuum Tube Amplifier Failure

[riq_ah]

I purchased my first tube amplifier not too long ago and was loving it. The amplifier is past its warranty. All of a sudden a loud squeal started coming out of the speakers. The noise was so unpleasant and couldn't be controlled to the point where i had to shut everything off. The sound was cutoff to the speaker as expected but the speaker still made the same loud squeal about 10 seconds after powering down. Eventually the noise decayed off. I removed signal cables leading to the amplifier and the problem persisted each time i repeated the steps above leading me to believe the problem is the amplifier.

Any suggestions as to what the problem might be or how i can begin troubleshooting?

 

[TLS Guy]

Well you have found out that tube amps are trouble prone.

I really can't help you. You did not state what amp and if you have a service manual and circuit.

It seems you are not experienced and likely have no test equipment. You need to stay out of that amp. Tube amps have very high voltages in the 350 to 450 volt range and you have to do service live. If you don't know what you are doing then you have a significant risk of having a half day out with the undertaker.

If you mess around without the right gear and knowing the voltage test points, especially bias voltages then you will get nowhere and do much more harm than good.

Unfortunately service techs have become a rare breed and those that deal with tube equipment rarer. My advice is to send the unit to the manufacturer for service and if it is a Far Eastern horror, I wish you good luck.

 

[M Code]

I purchased my first tube amplifier not too long ago and was loving it. The amplifier is past its warranty. All of a sudden a loud squeal started coming out of the speakers. The noise was so unpleasant and couldn't be controlled to the point where i had to shut everything off. The sound was cutoff to the speaker as expected but the speaker still made the same loud squeal about 10 seconds after powering down. Eventually the noise decayed off. I removed signal cables leading to the amplifier and the problem persisted each time i repeated the steps above leading me to believe the problem is the amplifier.

Any suggestions as to what the problem might be or how i can begin troubleshooting?

What is the brand of the amplifier tube unit?? Now adays there are multiple clone tube amplifiers with strange names built in China...
To me these look nice but have limited build and sonic capability... If the tube amplifier is from 1 of the traditional known legacy brands then more repair/service options are available. I do know a couple of very experienced service centers for tube amplifiers and could recommend 1. PM me for more details if U are located in Southern California.

Just my $0.02...

 

[PENG]

I purchased my first tube amplifier not too long ago and was loving it. The amplifier is past its warranty. All of a sudden a loud squeal started coming out of the speakers. The noise was so unpleasant and couldn't be controlled to the point where i had to shut everything off. The sound was cutoff to the speaker as expected but the speaker still made the same loud squeal about 10 seconds after powering down. Eventually the noise decayed off. I removed signal cables leading to the amplifier and the problem persisted each time i repeated the steps above leading me to believe the problem is the amplifier.

Any suggestions as to what the problem might be or how i can begin troubleshooting?

You shouldn't repeat the steps any more otherwise you risk damaging the speakers. Agreed with TLS Guy, it is hard to suggest any course of action without more information, but sending it to an authorized repair shop is a safe option.

 

[AcuDefTechGuy]

Buy a new amp. This time class AB or class D. Forget about Tubes.

 

[highfigh]

I purchased my first tube amplifier not too long ago and was loving it. The amplifier is past its warranty. All of a sudden a loud squeal started coming out of the speakers. The noise was so unpleasant and couldn't be controlled to the point where i had to shut everything off. The sound was cutoff to the speaker as expected but the speaker still made the same loud squeal about 10 seconds after powering down. Eventually the noise decayed off. I removed signal cables leading to the amplifier and the problem persisted each time i repeated the steps above leading me to believe the problem is the amplifier.

Any suggestions as to what the problem might be or how i can begin troubleshooting?

Hard to say without knowing what it is or seeing its schematic. From experience, if it squeals or howls, it's either a tube or a cathode connection issue.

There's a saying in electronics- 'All amplifiers are only a couple of values from being an oscillator'. The noise took time to decay because the filter caps needed to discharge.

If you have ever disconnected the speakers while the amp was powered, it's a very bad thing- tends to cause problems with the output transformers.