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russian tubes problems

mcdan

mcdan

Well-Known Member
Has anyone encountered as much trouble as I have had with Russian tubes?Tubes in question: Sovtek 5AR4 and JJ's, EH 5U4's too.
Shorts and grid leakage after less than 200 hours!
Similar with small signal tubes like 12BH7, 12AX7 etc.
Would be curious if others have had similar results.:thumbsdn:
 
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I don't handle the EH 5U4 so I can't comment directly, but one of my competitors uses them in guitar amps a lot and says they're good and reliable. The JJ 5AR4 has been problematic for people for a good while, the only ones I sell are tested under 120 ma. load.

The Sovtek/EH stuff is pretty bulletproof though, I've never had a bad 12BH7, and the 12AX7s are quite reliable. Right now, the Sovtek and EH stuff I'm seeing needs a lot of break in, they're pretty "sleepy" right out of the box; otherwise they are excellent. One caveat - above 450 volts I get a bit nervous about the Sovtek 5AR4.

How do you determine the tubes are shorted (I'm assuming rectifier shorts, am I correct?) or the small signal tubes are gassy? Maybe there's a clue there as to why you seem to have more than your share of trouble.
 
Rarely have probs with EH/Sovtek tubes. Only exception have been a few 5Y3 rectifiers and a run of EH 12AT7's that were highly microphonic. I won't use JJ or Ruby tubes. My experience with those has been early and high failure rates.
 
Celt said:
Rarely have probs with EH/Sovtek tubes. Only exception have been a few 5Y3 rectifiers and a run of EH 12AT7's that were highly microphonic. I won't use JJ or Ruby tubes. My experience with those has been early and high failure rates.
Click to expand...

Ruby is a rebrander, so it depends who made the tube if it's a good one or not. They rebrand almost all the current stuff - JJ, Chinese/Shuguang, SED, EH, etc. So a Ruby branded SED is fine, just like any other SED - and so on.
 
Nothing that I didn't already know. The problem with companies like Ruby and Groove Tubes is you never know what you are getting. I've had customers buy from both and have been sent mixed sets. I'm not taking chances with my customers. I'll go with what I know is reliable and offers good performance. Speaking of Russian tubes, so far I've been happy with the reissued Tung-Sols and Mullards.
 
I have had no problems so far with the Sovtek 5AR4. I use the Soviet Military equivalent of the 7189A, the 6П14П - ЕВ. They are performing well in my HH Scott 299 (first edition) amplifier.
 
Thanks for the replies. I guess I'm the lucky one when it comes to getting the bad apple.
 
mcdan said:
Has anyone encountered as much trouble as I have had with Russian tubes?Tubes in question: Sovtek 5AR4 and JJ's, EH 5U4's too.
Shorts and grid leakage after less than 200 hours!
Similar with small signal tubes like 12BH7, 12AX7 etc.
Would be curious if others have had similar results.:thumbsdn:
Click to expand...

Hello,

I am not denying your problems, but how can you get grid leakage
in a rectifier? Good luck finding adequate tubes.
 
Most current day production GZ34/5AR4 rectifiers appear to not have the reliability of the 'hayday' rectifiers of the late 50's through 1970.

My opinion of JJ, Sovtek, and Sino GZ34's is that they're each trying to produce a slightly better piece of junk than the other two. However, YMMV.

After replacing yet another failed new production GZ34 with a 1961 NOS Fat-Based Mullard exactly one year ago today, my Scott LK-72A really came to life, and other new production power tube's committed suicide.

I went back to mostly NOS, except for rolling different 12AX7's in the preamp section, and the amp sounds spectacular. No more arcing in the rectifier, no motorboating in the power tubes, no problems whatsoever.

. . Falcon
 
I ask that question myself! How does a diode have grid leakage? Yet when test the Sovteks each one shows grid leakage on one half. Different sides on each. (Sencore Mighty Mite) Put them in my MK-4's and blown fuses!
I do have one Mullard that tests perfect and performs great. Just have to find another at an affordable price.
 
FalconEddy said:
Most current day production GZ34/5AR4 rectifiers appear to not have the reliability of the 'hayday' rectifiers of the late 50's through 1970.

My opinion of JJ, Sovtek, and Sino GZ34's is that they're each trying to produce a slightly better piece of junk than the other two. However, YMMV.

After replacing yet another failed new production GZ34 with a 1961 NOS Fat-Based Mullard exactly one year ago today, my Scott LK-72A really came to life, and other new production power tube's committed suicide.

I went back to mostly NOS, except for rolling different 12AX7's in the preamp section, and the amp sounds spectacular. No more arcing in the rectifier, no motorboating in the power tubes, no problems whatsoever.

. . Falcon
Click to expand...

I could not agree more. I hate to use the Sovtek rectifier but as you may know, many sellers will strip the Mullard GZ34 (or HH Scott branded USA made by GE) and Telefunken 12AX7/ECC83 tubes out of a LK-48/72 or 299/222 and replace them with JJ or Sovtek or whatever. Watch their sales later and you may find the original Mullard/Telefunkens for sale. Hmmmm.

I am running a brown faceplate LK-72 right now. All original tubes, replaced capacitors (orange drops) and it just sounds fantastic. While I don't particularly like the current production GZ34, I have no problem with the Soviet Military replacement for the 7189A...
 
This might not be what you want to hear, but I think that tube rectifiers are among the things that really have been "beaten" by solid state. I'll use a couple 1KV Schottkys or even ultrafast diodes any day. As long as you derate properly, you can expect them to last basically forever. And they're cheap.
 
I would agree sorenj07, I see no need for tube rectifiers. I'm even looking at MOSFET amps although I've slapped myself for thinking it.
 
I've just replaced the diodes that were installed in my H-K Trio http://www.audiokarma.org/forums/attachment.php?attachmentid=86347&d=1207577486 by a good Sylvania NOS 5AR4. I did ask the question on another thread Trio Trio http://www.audiokarma.org/forums/showthread.php?t=158503 about the need or not to replace it. One point was that the other tubes were receiving the voltage all in a sudden instead of slowly and this surge could be bad for the tubes.

I also can add that I have a Reference 650 FET R which uses Hitachi mosfet drivers and that the sound is great, very powerfull, very neat. You can hear it doesn't hesitate at all when a huge bass punch happens ( my tenants doesn't like it... that's what I like... the punch). ALso, all the high freqs are very very precise and clean but it doesn't carry the warmth and the presence of tubes. It doesn't need ANY maintenance or yearly adjustment, NOTHING. Is that what you're looking for ?
 
Granted I use mainly Nos tube rectifiers, but I do not have any problems with them,
have replaced them with solid state and end up going back tubed, there's something
the tube rectifier does in the sound department that I very much prefer.

(Sorry not meant to derail the original thread intent)
 
I'm with Kegger - I prefer the sound of tube rectifiers. Of course I haven't tried the latest fast diodes except in my (few) solid-state projects.

If you have problems with modern production 5AR4s, I suggest the Japanese versions made in the 70s. Still fairly cheap - the Matsushita and Hitachi 5AR4s I have used in my equipment turned out to be excellent. Also make sure your PS capacitors are up to snuff. I'll also note that some amplifiers use too high of a value for the first capacitor - this can also lead to short life for anything other than the best-of-breed.
 
Hi.. Anyone using the Russian 5U4G/5C3S rectifiers?
Problem is: setting on bias voltage automatically drops to 0.93v from 1.2v when I changed from RCA 5U4GA to the Russian's! Will it be alright if I re-bias the EL34s in my Scott 250 Class A amps?

They're cheap, gorgeous and mucho looking. But sound wise ...??
 
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