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Help! Did my power cable blow his tube amp?

A

AudioTruth

Member
I sent my DIY power cable to someone, it has worked perfectly for months in my system. He plugged it into his tube amp and the aftermarket fuse blew in his $10,000 amp. He switched to his old power cable and his tubes blew, and another fuse. The fuses and tubes are worth $641, and he wants me to pay for them. Because he hasn't had any problems for 3 years, until switching the power cord to mine.

Is it possible that a power cable can do this?
 
It sounds fishy to me. Why did he use your power cable instead of his in the first place? If tubes are blowing before fuses then there's a serious problem with the setup.
 
mshan said:
http://www.analogbros.com/tech/articles/goodgobad.html
Click to expand...
I found this:
Tubes do wear out over time. In addition to the sudden failures such as shorts mentioned above, as the tube ages, several mechanisms are at work. Most common are mechanical problems, in which the internal geometry is altered as the tube undergoes numerous heating/cooling cycles and is subject to physical shock. (TIP -- to prevent this, don't move your amp while the tubes are hot). These changes can manifest themselves by way of increased microphonics, hum, and other noises, or loss of gain and even shorts.
Click to expand...

So the physical shock from unplugging and plugging in the other cable damaged the tubes?
 
Unfortunately I don't know.

Fact that it happened right after he plugged in your power cord suggests it might have something to do with the power cord, though.

Tubes dying of old age I think would manifest like article says, hum, microphonics, noise, maybe loosing frequency extremes and dynamic pop.

Not sure if this is consistent with electrical physics, but perhaps you had a much larger gauge conductors vs. stock cord and amp saw a sudden surge of current it was not designed to withstand?
 
mshan said:
Unfortunately I don't know.

Fact that it happened right after he plugged in your power cord suggests it might have something to do with the power cord, though.

Tubes dying of old age I think would manifest like article says, hum, microphonics, noise, maybe loosing frequency extremes and dynamic pop.

Not sure if this is consistent with electrical physics, but perhaps you had a much larger gauge conductors vs. stock cord and amp saw a sudden surge of current it was not designed to withstand?
Click to expand...

What you posted previously was good info but, a larger gauge conductor does not magically pump more juice to the amp. Larger gauge connectors have the ability to carry more amperage but, the amp determines how much it draws. You're suggesting that the old cord limited the amount of power the amp could draw would mean it must have glowed in the dark. 🙂 Although, that would explain why he was using a different power cord but, if so, that would mean he's an idiot and the OP is not to blame.
 
Sounds like a crock of shit. It's a power cable, three wires with plugs. The only thing that I can imagine you could have done wrong would be to short two of the wires together (which would probably trip the breakers on the house) or wire up the connections incorrectly. But since the fuse blew, he should not have suffered any damage to a properly designed amp. The fact that the fuse blew again when the old power cable was installed suggests that there is most likely some kind of electrical fault to be found in the amp or the tubes. Most likely, one of the tubes was already on the out and that was what blew the fuse originally. The guy's failure to test the tubes and check the system for faults after the fuse blew the first time exposed the tubes to additional shorting and bad behavior when he started it again.

Three years is not unexpected for tube life, especially if he kept the amp on the whole time. Most tubes I would expect to last 2-5 years depending on usage.
 
Following up on what Born2bwire said, ask him if he tried some NOS (new old stock) tubes that might not have been fully tested by seller he bought them from before your friend put them in the tube amp.

If he was swapping out various tubes to see which combo he felt sounded best around same time that he tested out your power cord, it could very well have been an issue with faulty tube, not your power cord, that was ultimately responsible for amp blowing up.
 
Fuses are there for a reason. I've had fuses blow due to shorts, but I've never incurred damage because that's why they are there. I'd check a couple things:

1. Check you're cable for damage. If there was a real short, there will likely be some sort of evidence. Check the connectors and and anywhere you have a splice for burnt rubber or discoloration . I agree with born2bwire. It's a power cable...a simple thing. As long as the gauge is larger than required for the amps, phases are matched and the splices are sound, it's a simple connection.

2. You mentioned he was using an aftermarket fuse. Was this fuse properly rated for this application? Bad tubes can overdraw amps and it's possible that it was actually a chain of events that happened. If the amp draw increased past damage point but the fuse was a bit too big then that is a problem. Now saying this is what happened..just thats its possible. Even with a properly sized fuse its possible, because if the amps stayed just below tolerances without spiking it could do alot of damage before the fuse going.

Was there something extraordinary about this setup that wasn't accounted for? Now, this is the part where I might get some heat for. As it was said, why did he use your cord if his was available. My personally belief is that when he opted to use your hand made cord, for whatever the reason, instead of seeking out a professionally made one he assumed the risks. If he paid an electrician to make one and it failed due to incompetence, he might have a case in small claims. Ultimately you have to decide how to handle it, but I don't think your liable for the damages. You might decide to kick in some money because he's your buddy, but don't let him railroad you into paying for damages that he truly can't prove was your fault. Correlation does not equal causation.

Hell, if you can prove the fuse was improper for the job, you could build a case where he should replace your cable! I'm jesting of course, but it's easy to see how this is a crazy situation.
 
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How would your power cable be responsible for the blown fuse and tubes when he switched back to his old one? What could your cable have done that would make those blow when he used a different cable?

I'm no electrical engineer, but that makes no sense to me. I can understand how a faulty cable can do major damage, but I don't see how it can have a residual affect when he switched it back.

Where is your DIY cable now?
 
AudioTruth said:
Yes, and now he says I'm responsible and I need to pay. He has used the tube amp for 3 years and never seen anything like this.
Click to expand...

fuck him. Tubes are wear items.


If there was a short at your power cable, the electric panel breaker should have tripped.
 
Anyone with any basic understanding of electronics can tell you that it's not your cable's fault.

Back when XBOX 360 consoles were still dropping like flies, everyone would blame the latest update or big game release when the actual correlation was that XBOX 360 consoles needed to be USED to die like that and those things would trigger usage. If it's been "fine" for months until you bought that major release and started playing it, it's likely that you weren't using it as much and it wasn't going through the heat/cool cycles. Also, using more can have a preventative effect if it reduces cycles, so going into storage for a "deep cool" and then breaking it out can trigger a failure (using all day is less cycles than using twice a day; more oil drains out of an engine the longer it sits between warmups; etc).

People are WAY too quick to use the "everything was fine before X" explanation when, well, if it's going to fail anyway, it's gotta fail sometime, and it can't always be the fault of the last thing you changed or did differently just because it worked before.
 
who buys a $10k amp and does not replace the power cord with an approved brand new one from manufacturer?
I mean i'm sure your cable is awesome, but seriously, if he can afford $10k for an amp, he can afford to replace with approved parts and replace the tubes and fuses as he had to know there was a possibility of those tubes going bad before their supposed to anyway.

i'd tell him to legally prove it but he's obviously a scammer.
 
Anteaus said:
Fuses are there for a reason. I've had fuses blow due to shorts, but I've never incurred damage because that's why they are there. I'd check a couple things:

1. Check you're cable for damage. If there was a real short, there will likely be some sort of evidence. Check the connectors and and anywhere you have a splice for burnt rubber or discoloration . I agree with born2bwire. It's a power cable...a simple thing. As long as the gauge is larger than required for the amps, phases are matched and the splices are sound, it's a simple connection.
2. You mentioned he was using an aftermarket fuse. Was this fuse properly rated for this application? Bad tubes can overdraw amps and it's possible that it was actually a chain of events that happened. If the amp draw increased past damage point but the fuse was a bit too big then that is a problem. Now saying this is what happened..just thats its possible. Even with a properly sized fuse its possible, because if the amps stayed just below tolerances without spiking it could do alot of damage before the fuse going.

Was there something extraordinary about this setup that wasn't accounted for? Now, this is the part where I might get some heat for. As it was said, why did he use your cord if his was available. My personally belief is that when he opted to use your hand made cord, for whatever the reason, instead of seeking out a professionally made one he assumed the risks. If he paid an electrician to make one and it failed due to incompetence, he might have a case in small claims. Ultimately you have to decide how to handle it, but I don't think your liable for the damages. You might decide to kick in some money because he's your buddy, but don't let him railroad you into paying for damages that he truly can't prove was your fault. Correlation does not equal causation.

Hell, if you can prove the fuse was improper for the job, you could build a case where he should replace your cable! I'm jesting of course, but it's easy to see how this is a crazy situation.
Click to expand...


Check the aftermarket fuse.

Besides current rating, fuses are rated by how fast they blow. A "slow blow" could have been substituted for a "fast blow" and that could have allowed sufficient over current exposure to damage the circuits of the amp/system.

http://electronics.stackexchange.com/questions/25055/slow-blow-vs-fast-acting-fuse
 
Sounds like a scam to me. Your power cord should only effect the house wiring, or be an open circuit. Unless there is a possible way that it could be hooked up incorrectly. Posting pictures of the power cable would help.
 
He already ran it on his equipment though, it worked fine.

Unless it was on a diy amp of his and the power socket on him amp was also wired wrong to match...
 
Could the fuse in his tube amp have blown because my cable was too thin for his power hungry amp? My cable is 15awg and I live in Europe, he lives in USA.
 
I wouldn't think so, the cord may feel warm depending on the current though.

According to Wikipedia 14awg can carry 20/20/25 amps at 60/75/90 degrees C rated insulation respectively. They don't show 15awg current ratings, but 16awg was rated at 18a @ 90 degrees C
 
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If his tube amp is pulling 18 amps then it would nearly have to have its own circuit in his home. Most typical household circuit breakers are 15 or 20 amps.
 
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