Replacing tubes needs often special attention. The combination of some specific designs, and users which are not qualified to service amplifiers, causes problems.
Contents
Introduction. (You are already here)
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 instructions which are with the new EML tubes, and ask when they are not sure what to do.
But, unfortunately, it is not always like that, and some users just replace the tubes without thought. .
Then, if a problem does occur, comes the usual swapping of the bad tube, from the left to the right channel, and this seems to verify the cause is 'the tube'. Well at that moment, yes. But how could this have happened? If both tubes are mistreated, there is no rule saying, they must get equally bad, at the some moment. Likely one gets bad first. So you can plug the bad tube from the one channel to the other, or in another amplifier, and of course 'problem follows the tube'. What does this tell you? Well me it tells only, one tube works, and the other not. It tells nothing about the reason.
Really, you are so much better off, 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 a trap for buyers of new equipment. When the day comes you need service information, they may not give it. 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.... it WORKS. Then, the crying becomes loud when a tube gets defective half a year later. Some users require free replacements, but then it becomes really strange, if they have the only intention to repeat the failure. Meaning again they will blindly replace the tube.
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 20% too high voltage. They work very satisfactory for some weeks, and you think you did it right. 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 ligh bulb was bad'. Now guess what happens if the seller replaces the bad lamps to you? The failure will repeat, of course.
Most errors occur in this order:
- Emission problems, due to wrong heater voltage
- Thermal overload of the whole tube
- Spark effects inside, due to in-rush current out of specification
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.