Author Topic: Has anyone else had bad luck with Sovtek 5AR4s lately?  (Read 555 times)

midwayfair

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Has anyone else had bad luck with Sovtek 5AR4s lately?
« on: November 25, 2019, 07:02:37 PM »
I blew up one of them in my Tone King Imperial maybe a year ago, and killed two of them in my little 5W before I gave up and swapped it out for a Weber solid state thingie. (So I know it's not something I can't find wrong in one of the amps.) Turned on the tone king yesterday and the 5AR4 is going again. I don't play the amp that often and it use to take me years to kill one playing it often.

I don't think Sovteks are crappy tubes, and I'm not really sure what to try instead. I would think that the Tung Sols are made in the same factory and JJs are made in China so not too likely to be more reliable. Anything else out there I should look for?
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Ralfg

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Re: Has anyone else had bad luck with Sovtek 5AR4s lately?
« Reply #1 on: November 25, 2019, 08:05:26 PM »
JJs are actually made in the Slovak Republic and I find them to be pretty reliable. I have their rectifier tube in 2 amps and never had a problem. I think Chinese tubes get a bad rap that isnít quite deserved. An amp tech told me that JJs and Chinese tubes are really the only ones made to spec and some of the only tubes you can use for the cathode follower position. Donít know if that is true or not. You could also try a Ruby rectifier tune, itís just a re-labeled Chinese tube but tested for quality. I did have a sovetek and a Mullard (all under the New Sensor) go bad on me.
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gordo

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Re: Has anyone else had bad luck with Sovtek 5AR4s lately?
« Reply #2 on: November 25, 2019, 08:22:14 PM »
+1, I've had great results with JJ's, although honestly I've done well with Ruby's and GT's as well lately.  Even the TubeStore recommends the JJ  5AR4, or if you want to get spendy, the Genalex or Mullard.

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Re: Has anyone else had bad luck with Sovtek 5AR4s lately?
« Reply #3 on: November 26, 2019, 05:40:19 AM »
Might be worth checking out 12voltvids on YT. In the past week he had a similar issue with a rectifier in a Dynaco build.  He also made a video fixing it as well.
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ahiddentableau

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Re: Has anyone else had bad luck with Sovtek 5AR4s lately?
« Reply #4 on: November 26, 2019, 02:07:41 PM »
I don't know what it is about 5AR4s but I've heard people complaining about problems with that model for years now.  I normally like JJ tubes just fine (and I've never had any problems with a JJ other than this one and a stray EL84 that blew quickly), but my 5AR4 from them blew out in record time.  This in a 15W Lightning style amp.

FWIW, the people at the Trinity Amps and many of its forumites all swear by the Chinese tube.  They say they aren't super fond Chinese tubes in general, but that their 5AR4s are better than the Russian and Slovakian models that are currently being produced.  More robust, they claim.  They're cheap as chips so it might be worth a look.

midwayfair

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Re: Has anyone else had bad luck with Sovtek 5AR4s lately?
« Reply #5 on: November 26, 2019, 09:54:23 PM »
The Tube Store's preferred series is made in China. I might pick a couple of them up. But it's good to know that I'm not crazy and that some other people have had trouble.

Worst comes to worst I'll get another Weber solid state converter or steal the one from my 5W and convert it since the tube rectifier is pointless there anyway.
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Re: Has anyone else had bad luck with Sovtek 5AR4s lately?
« Reply #6 on: November 27, 2019, 10:33:20 AM »
Not sure it applies to the Tone King but just to throw it out there...

My AC30CC head shipped with a Sovtek 5AR4 for the rectifier and it always had what I like to call "undefined strangeness". 

I read this article:
https://www.premierguitar.com/articles/Ignore_a_Modern_AC30s_Standby_Switch

I bought Weber Copper Cap as a replacement and everything has been fine since.

The CC series had a bad rap for being unreliable which I believe is almost entirely due to the retifier tube. In the next "C" series Vox changed to a solid state rectifier.

I think the Copper Cap actually made mine sound better and I don't need to use the standby switch anymore.

midwayfair

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Re: Has anyone else had bad luck with Sovtek 5AR4s lately?
« Reply #7 on: November 27, 2019, 12:37:01 PM »
Not sure it applies to the Tone King but just to throw it out there...

My AC30CC head shipped with a Sovtek 5AR4 for the rectifier and it always had what I like to call "undefined strangeness". 

I read this article:
https://www.premierguitar.com/articles/Ignore_a_Modern_AC30s_Standby_Switch

I bought Weber Copper Cap as a replacement and everything has been fine since.

The CC series had a bad rap for being unreliable which I believe is almost entirely due to the retifier tube. In the next "C" series Vox changed to a solid state rectifier.

I think the Copper Cap actually made mine sound better and I don't need to use the standby switch anymore.

Unfortunately I've already been ignoring standby switches forever :P I didn't even put one on my 5W. (Merlin Blencowe's book recommended against them.)

I would just go to the copper cap already but I like some of the sag in the power amp when I get to turn it up.
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Re: Has anyone else had bad luck with Sovtek 5AR4s lately?
« Reply #8 on: November 27, 2019, 02:07:04 PM »
Sounds like a mystery to me Jon!  It may be the tubes, or could there be other factors compounding the issue?
What's the heater 5AR4 voltage looking like?  Power surges in your area can weaken the rectifiers... perhaps you could install MOV for transient suppression on your incoming Hot and Neutral wires.  Too much Filter Capacitance can strain the rectifier... see the datasheet.  You can 'pre-rectify' the 5AR4 using a couple of 1N4007... it can lengthen the Tube's life by increasing the PIV of the combined ss/tube rectifer... also it provides a fail-safe in case of rectifier short.
That's all I can think of for now... hope you can figure it out :)

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Re: Has anyone else had bad luck with Sovtek 5AR4s lately?
« Reply #9 on: November 27, 2019, 10:11:06 PM »
Just at a complete guess, what is the wall voltage where you are, what kind of voltage increase is the 5AR4 seeing as a result?

I heard somewhere that the original JTM45/100 circuit values were worked out to just this side of blowing up valves, voltage wise, and that USAian wall sockets run at 120 to 130V these days, not the nominal 110V, and this pushes old 45/100 circuits past that point.
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midwayfair

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Re: Has anyone else had bad luck with Sovtek 5AR4s lately?
« Reply #10 on: November 28, 2019, 01:16:18 PM »
Just at a complete guess, what is the wall voltage where you are, what kind of voltage increase is the 5AR4 seeing as a result?

I heard somewhere that the original JTM45/100 circuit values were worked out to just this side of blowing up valves, voltage wise, and that USAian wall sockets run at 120 to 130V these days, not the nominal 110V, and this pushes old 45/100 circuits past that point.

Wall voltage here is 120V. The Tone King is a modern design amp and it's pretty overengineered. It's not a vintage amp repro or anything. It's designed to use a 5AR4 and the Sovtek is the spec'ed tube in the user's manual. This one's from 1996 or something and it never had this problem until like 2016. I got it in 2012 I think. The first couple rectifier tubes I put in it (also Sovtek) lasted >2 years under much more constant use and I only replaced it because I thought it might be getting old, not because it failed. I built the 5W in 2015 I think, and it used to get hand-me-down tubes.

Edit: I'm not sure what the maximum voltage is for a 5AR4, but I'm pretty sure the difference between 110 and 130 isn't significant enough. Peaks should be above 130 even with 110V. The capacitors are the most likely things to fail with extra voltage, because if you're pushing 110V up to 400 and you're using 450V caps, then you're probably going over that when the wall voltage gets to 130V.

I think the unfortunate thing here is that I don't have a great way to test anything here. Maybe it was a bad couple of years and they're fine now, but it would take me years to figure that out, because it's not like they fail right away ... hmmm, maybe I need MOAR TONE KINGS. Mmmm.
« Last Edit: November 28, 2019, 01:21:53 PM by midwayfair »
Myself's music & things I make: http://jonpattonmusic.com. My band: http://midwayfair.org. PCBs of my designs from: http://www.1776Effects.com (Bearhug Comp & Cardinal Harmonic Trem); http://www.jmkpcbs.com (Hamlet+ delay & Blue Warbler envelope vibe); Snow Day OD/Flabulanche: www.madbeanpedals.com