I have had my tube amplifier for about 2 1/2 years. I listen to it pretty much daily for a minimum of two hours a day. How long can I expect the rectifier tube to last.?
I guess the answer depends on a lot of factors. If it is a quality brand rectifier operating quite a bit below its maximum ratings it should last several years, if it is a Sovtek GZ34 it should have arced over two years ago 🙂
You will experience a drop on B+, less power, increase distortion etc. Another indicator, the obvious one, the filament does not lights up 🙂
I think it was John Broskie, I could be wrong, that recommended using two diodes as shown. It is supposed to prolong the life of current-production rectifiers. They could be 1N4007 or HER108, whatever you fancy. Or it could have been George of Tubelab.com. My memory fails me at times.
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That’s the arc-over protection. The silicon actually provides the reverse blocking needed and you still have “tube rectifier” characteristics. Lifetime will be limited by cathode emissions, just getting weaker over time like they did in the old days. Surprise “ka-pow” won’t happen.
And replace the tube with a resistor (for a similar IV characteristic).
I would never design anything to use a vacuum rectifier these days, but I’d put one in an old piece of equipment which called for it. And use the diodes. You’d still see a nice pretty vacuum rectifier tube on top of the chassis.
I would never design anything to use a vacuum rectifier these days, but I’d put one in an old piece of equipment which called for it. And use the diodes. You’d still see a nice pretty vacuum rectifier tube on top of the chassis.
Well... except that the rectifier tube's forward voltage drop and sag characteristics with load current may be sonically desirable. The tube rectifier can carry on doing that; the silicon diodes protect modern tube rectifiers from arcing.
Cheers, and regards,
Ant.
Fair point for an instrument amp... These characteristics are undesirable for hi fidelity playback IMHO.
The short answer is probably 3-4 years, at that rate. But really, it's not a bad idea to replace your tubes every 3-4 years to keep the amp sounding good. Preamp tubes are different, they can last for longer than that because they're not being put to such stress.
Sadly nearly every owner of a valve amp has no awareness or skills or equipment to check whether their rectifier valve (or for that matter output stage valves) are still performing adequately, apart from the reactive response to no sound output, or smoke. Your amp may have been designed to cope with a faulty rectifier valve by failing benignly, but many amps have not had such luck and again few owners have the skills to update their amp with modern protection measures like in post #5.
Hopefully you have budgeted for replacing valves that do have relatively short service lives, and have a calendar reminder to do just that, but again sadly not all valves are replaced with the same performance valve due to varying manufacturers over the decades. You just need to cross your fingers and appreciate that valve equipment can fail - just hopefully rarely.
Hopefully you have budgeted for replacing valves that do have relatively short service lives, and have a calendar reminder to do just that, but again sadly not all valves are replaced with the same performance valve due to varying manufacturers over the decades. You just need to cross your fingers and appreciate that valve equipment can fail - just hopefully rarely.
Best thing is to find someone who can test tubes. Aim to have one set in reserve, and get the other set tested when you get the chance, discarding below par tubes. My Funke W19 manual sets quite a low bar for OKAY tubes - 60% of published specs.
Rectifier tube life is related to . . .
The quality of the rectifier tube.
How hard the rectifier is run, peak current, rms current, peak plate voltage, voltage range of the filament voltage (voltages change as the power mains voltages change), power transformer primary DCR, secondary DCR, input capacitor uF value, cap input filter, choke input filter, etc.
A Ferrari engine that is always run at 10,000 rpm will not last as long as one that is always run at 6,000 rpm.
Many rectifier tubes operate very well for decades.
The quality of the rectifier tube.
How hard the rectifier is run, peak current, rms current, peak plate voltage, voltage range of the filament voltage (voltages change as the power mains voltages change), power transformer primary DCR, secondary DCR, input capacitor uF value, cap input filter, choke input filter, etc.
A Ferrari engine that is always run at 10,000 rpm will not last as long as one that is always run at 6,000 rpm.
Many rectifier tubes operate very well for decades.
So i have installed the diodes ahead of the 5AR4 in my Dynaco ST-70. The voltage at the first rectifier dropped from 435V to 420V. Not too happy about that. I guess the UF4007s are contributing their own voltage drop.
Get one of these and never have to bother changing it again 🙂
https://tubedepot.com/products/solid-state-rectifier
https://tubedepot.com/products/solid-state-rectifier
Check for something else going on. The two UF4007 diodes, if correctly installed, are not responsible for the 15V drop that you observed.
Get another new/good tube and put it in the amplifier, if you don't hear/notice a difference, put the old tube back in.