I had a tube circuit go bad in an ARC CL-60.
I wasn't aware of it until I traded it in for a new VT-100 MK-I.
The store owner said a resistor burned out but, again,
it wasn't detectable sonically.
I did play at very conservative volumes so maybe this helped mask the problem.
This was one tube in a four-per-channel stereo amp. |
First of all relax & enjoy your amp. Properly biased your tubes should last a long time. If one of your power tubes goes you will blow a fuse. You will not have a fire. I have a Yaqin intergrated MC-10T amp in one of my systems and it has run for a couple years without issues and sounds great. |
Usually, tubes just get old and weak. The sound will lose dynamics, may sound "gummy" and less volume. That's the time for new tubes.
When a tube amp altogether fails, that's not a desireable thing...
The small tubes usually last 3,000 to 10,000 hours. Output tubes such as EL34 will last around 1,000 hours. |
Any or all of what you mentioned can happen.
Chuck |
ARC amps utilizing 6550's are notorious for going out with a nerve shattering mini explosion and smoke! An ARC tech told me it is the nature of the tube. Typically, there is a resistor adjacent to the failing tube that burns up, sometimes damaging the circuit board. Having experienced it several times, I have become wary of these amps. Makes me nervous and thus I have switched to SS power amps. Their preamps with small tubes are great without this tendency. On the other hand, Wolcott power amps based on EL34 tubes do not do this. When a tube fails, the amp keeps playing, and a an indicator tells you which tube needs replacing. Simply swap it out. |
A tube failure, i.e. it stops functioning, can:
1) Stop sound in the channel it is assigned to. Both channels if it works in both channels. A small tube will usually stop the sound from one channel and will usually go out quietly. A power tube can go out quietly by will more often go out with a 'pop' and/or an electric light show in the tube or a reddening of the tube plates. If a power tube goes out with a pop it will often take out a fuse or a resistor in the bias circuit.
2) A partial failure in a small tube can produce a 'snap/crackle/pop' (this could also be produced by poor contact with the poins and tube sockets).
3) Sonic degredation which is most easily determined by simply having a set of replacement tubes on hand for emergencies in any event and substituting these tube for a few days and see if you can hear any meaningful improvement.
4) All manner of gremlins associated with any audio equipment (but usually easier to fix with tube stuff).
Learn to relax and enjoy your new toy! :-) |
I would like to add to Newbee's first item that the 'pop' can be very loud. When one of the output tubes in my MC2000 went, I thought at first that someone had fired a gun right outside the window behind the amp. It took out a resistor, too. The amp was idling at the time.
Bill |
I had a rectifier tube go (one of 2 5ar4s), and didn't notice till the next day. Usually they go gracefully, and no pasa nada. However....once, a 300b went supernova. Quite impressive, but heart stopping to say the least. That event took out a couple caps and a resistor or two. The good news is MANY tube amps aren't that complicated to fix. Point to point is obviously the easiest.
As has been said, enjoy. In more than 10 years with this amp, only once did anything serious occur. And it really wasn't that serious.
Rob |
Add a little more excitement in your life and enjoy tubes.
It makes life a bit more worth living! |
What happens when a tube amp fails....the repair tech rings his hands in glee. |
I've had a peaceful coexistence with tubes for over 10 yrs now. There have been a couple of instances but a fuse was all that "went". Cause in both cases was a short in the rectifier.
I have a tube tester and that helped identify the shorts immediately. I do test tubes with it but I think the best test is to have a backup set and put them in once a year to "test" against the aging ones. |
I have seen, and heard, various modes of failure, but, amazingly, not at all in my own gear. All I've had to do was replace tubes that have started to go weak (sound becomes dull and muddy).
The most interesting was an amp at a dealership. I went there with the intention of buying the amp after a couple of auditions. The dealer offered to turn it on for one more listening. Something in the amp instantaneously vaporized (probably a resistor) and what I saw as a tiny mushroom cloud rising from the amp.
On another amp at a dealer, a bad tube socket would cause a loud pop through the speakers once in a great while; that pop was spectacular and quite unnerving to me. A friend borrowed the amp from the dealer not knowing about the condition and put them on his 105 db/watt efficient speaker. He said the "pop" rattled the windows and shook the whole room.
If you really want a big surprise, try accidentally wiring into a circuit a polar capacitor in the wrong direction--big bang and capacitor bits everywhere. |
Wow!, I have owned tube equipment,always went on to the next componet before failures, never went thru these scenerios!, thinking of buying a tube digital source that I once owned before, that sounded magical to me, looking at all that has been said here about tube failures has me having second thoughts, solid state now seems ever more appealing. |
Sheesh. The tube amps have the tubes in sockets for a reason. The reason is they are user-replaceable, like a light bulb.
The usual remedy is to install a new tube when one fails. Its not rocket science.
Some power tubes will require some adjustment of the amp, the procedure should be in the owner's manual. Some amps have auto bias and little if any adjustment is required.
It is true that many power tubes fail due to arcing as the cathode structure degrades and starts falling apart. The prudent manufacturer will build the amplifier to withstand this sort of behavior, but oddly enough we do continue to hear about amps that smoke when a tube fails! That says more to me about who built the amp than it does anything about the tubes... We've been seeing tubes arc for as long as there have been tubes, this sort of thing should be sorted out. I avoid amps that have this sort of design problem.
An example of a tube amp that holds together with tubes arcing is the Dynaco ST-70. Now if Dynaco could make that happen way back in the late 1950s you'd think it would be a walk in the park for a manufacturer from the 21st century :) |
I would guess that manufacturers that don't solve the problem of the tubes arcing think that the necessary changes the amplifier will in some way have a negative effect on the sound quality. Less if more, right...right up until the time it fails. |
or perhaps its good for business when resistors & parts blow:) |
