Problems with tubes and amplifiers
Contents
Introduction. (You are now here)- Consider all possible factors
- Specific Amplifiers which need special attention
Introduction.
I am glad to say, problems with Emission Labs tubes are very rare. That is also because when replacing tubes, most users read the amplifier manual, and the instructions which are with the new EML tubes. Then, if unsure, most users ask for advise.
But, unfortunately, not all users are that wise. Some just replace the tubes without any thought. Then, if a problem with one tube occurs, instead of asking what to do, they begin tp do experiments. Without any knowledge of tubes, or knowing how electric circuits work, they swap the tubes from the left to the right channel. Now imagine this stupidity. Suppose the amplifier damaged one of the new tubes, now the other tube also gets damaged. Or, of the tube was faulty indeed, now the other channel gets damaged. It doesn't have to be like that, but there is a risk, and when it goes wrong they say the amplifier was good, because it worked well on the old tubes. But you see, the tubes worked also well, before they were send. Really, if your car has a problem with the right front tire, would you swap the right and left wheels? I would say that is a pretty dangerous thing to do when you know nothing about tires, or how a car is constructed.
You are so much better off, to first read the documentation before servicing a tube amplifier.
Luckily, such amplifiers exist, where you can blindly replace tubes indeed, and these are ideal products of course. But, before you think yours is like that, check that in the manual. Some other amplifiers are simply not like this. Manufacturers have sometimes the standpoint, users must send in or bring their amplifiers for a tube exchange. Needless to say, shipping tube amplifiers by post, every normal person will try to avoid it like monkey plague. But often this situation is provoked, by keeping documentation 'secret'. This is am evil trap for buyers of new equipment. Luckily, in 2026 the European Union will forbid manufacturers this bad practice, but legally it can only be done for new sales. So when the day comes you need service information, they may not give it if the amplifier was made before 2026. So I recommend always, DO NOT buy an without service documentation and the schematic, because the day will come, you need it.
Yet, it is a repeating problem, when no repair person can find be found near by, what shall the poor owner do?! Some amplifiers weigh 20kg or more, and need dedicated shipment crates, to send then to the other end of the world. So, people try to do the exchange themself. Carefully plug the new tubes in, and hey.... they WORK. Then, the crying becomes loud when a tube gets defective, half a year later. Some users require free replacements without finding out the problem cause. They say they already know: It's the tubes anyway. What they mean by that is, they expect new tubes for free, and they are going to repeat the procedure. Well, that will only repeat the error, whatever caused it.
Please take the above with a grain of salt, but is does reflect the things we see. Try the following: Operate two light bulbs at 120% of the rated voltage. They work very satisfactory, burn very bright for some weeks, and then suddenly, one will fail without warning. So you swap the broken lamp in the other socket, and yes, the problem follows the lamp. So you found the failure reason: 'The lamp was bad'. Now guess what happens if you replace the 'bad' lamp with a good one. You can repeat the failure as often as you like.
Most errors occur in this order:
- Emission problems, due to wrong heater voltage
- Thermal overload of the whole tube
- Spark effects, due to absurd in-rush current
- DC coupled amplifiers with design stupidities
In the following pages, we want to give some background about how to prevent problems, by correct installation.
With power tubes, such as EML builds, if the root cause is the amplifier, replacing the tubes will only repeat the problem!
For instance, somebody has broken tubes in a 220V amplifier, which was plugged into a 235V mains. He was never interested in the mains voltage, and does not even know very much what that is. So logically he will say, 220V or 235V, was never a problem all of my life, so why is it now?
When we analyze this, it means he expects tubes to work fine in a 220V amplifier, which he plugs into a 235V mains. He feels this should be possible because it never went wrong. At this moment, already the conclusion is wrong. The users says it never went wrong, but it fact it DID go wrong, because that is what we were talking about.
In short, if a blind replacement appears to be possible, does not mean this was possible to do. You would find out the mistake only after a broken tube, but it is too late then.
These pages just try to give some assistance. Good users manuals are rare. So at EML we try to help you out, when manufacturers play the usual a hide and seek game with schematics and manuals, but it is assistance only. We do not have responsibility for the amplifiers, and if they let you down with 'secret' schematics, some just do it.
Please note, in Europe it is planned starting in 2025, that manufacturers are obligated by law to supply whatever information it needs, to perform a repair yourself. It is called 'the right to repair'. This means the seller must provide at reasonable costs, whatever it takes to repair a product, for 5 or 10 years. Nothing is excluded from that. So secret tools, hidden adjustments, calibration tools and software, schematics, everything. In case the seller is indeed not able to give the obligated support, that excuse is not working, because then he sold a product not conforming to the law, and he must take the product back. That is going to be interesting, when Tesla car owners want to have at self cost, the procedure and the software needed, to service the battery in his own garage.
Part 1. What to do in problem cases.