Modern 5y3s

[bluzmn]

I think I read on this forum (or maybe on another one, because i couldn't find it with a search) that 5y3s being manufactured today are no good, but I don't remember the reason. Could someone please remind me? And I do have an NOS 5v4; would that be a suitable substitute?

[Justin Thomas]

What I've heard is that the modern 5Y3s don't drop enough voltage in a vintage amp that was designed for one, and so filter caps and other components may suffer undue stress or suddenly fail when a new replacement is fitted. I've also heard that Sovtek 5Y3s are basically "GZ34 rejects," because they don't meet the higher specs, but they still "work." So label them as something less... That said, I've never seen a Spvtek 5Y3, so I don't know what the innards look like to compare. Also that said, I have never had a rectifier tube in any of MY amps short or fail, regardless of what brand or date they were. I HAVE repaired several amps that suffered a blown rectifier, but they also had blown fuses and/or power tubes/filter caps.

When buying new, I use JJ. Of the 3 I've had, all work fine. As far as a substitute, they pretty much will all "work," but in the case of using a 5V4 in place of a 5Y3, watch out that your voltages don't rise and blow any other components, mainly filter caps. I'm now partial to 5R4s, myself - drops as much voltage as a 5Y3 but takes higher input voltages & output currents.

Justin

[g1]

Justin is correct, it's a higher than normal voltage problem with the Sovtek's (unless they have now changed). I recently got one and had to exchange it for a different brand (JJ) because the voltage it put out was too much for the vintage amp to handle.
The sovtek that I was first given was older stock, so it is possible they have corrected the issue but I don't know and wouldn't take a chance again.

[Tubegamblar]

The only one that I did find out to work as they should are the JJ 5Y3S, good price also, at least here in Europe. Personally I don´t ever use a 5v4. Only my humble opinion. Let's hear others so it is interesting.

[Justin Thomas]

Why not a 5V4? Just curious. I also have a couple. I didn't use one in my last build for some reason, though I forgot what it was. Maybe too high AC input voltage?

Justin

[Leo_Gnardo]

I've also heard that Sovtek 5Y3s are basically "GZ34 rejects," because they don't meet the higher specs, but they still "work." So label them as something less...

That's the story I've run across - Sovtek (and any other New Sensor brands eg. TungSol, ElectroHarmonix, Svetlana, Mullard, others) 5Y3 don't have the "sag" factor consequently deliver significantly more high voltage than expected.

I get new 5Y3 from Ruby, made in China and tested by Magic Parts, never a problem. They perform as expected.

It's possible JJ's are also OK, haven't tried their 5Y3 yet.

FWIW JJ had a bad QC problem with GZ34/5AR4 about 5 to 7 years ago. Any still left on the sales shelf from then, bad news. There's no manufacture date printed on tube or box, so if you get stuck with those, you're hosed. In recent times I haven't heard anybody having problems with them, in fact JJ seem to have been on an overall improvement track.

[Justin Thomas]

The only Sovteks I like to use are the 12AX7s & those damned-near-indesructible 5881WXTs. The one set of TSRI 5881s I got redplated in my Bassman head and cathode-biased Prosonic, and every EH power tube I tried blew up with a short. Well, okay, it was only a single 6V6, but... I refuse to give you another chance to blow up my Champ!

I only use the stuff that's branded Sovtek, no fancy labels for me... Chinese pre tubes in function positions - too microphonicer for gain stages... otherwise it's JJ or some of my used but still good or NOS stash. Most of my best tubes come from scavenging...

Justin

[Diablo]

Why sweat the problem with new production 5Y3? There are so many good used vintage 5y3 tubes out there that you can buy them for peanuts. You can even buy NOS for cheap if you're so inclined.

[bluzmn]

To answer Diablo, I had already bought a Sovtek 5y3 when I read somewhere about the problem with voltage drop. I'm planning to put it in a Joyo JTA-05, which comes with a 5ar4 installed, so the voltage shouldn't be a problem. I've heard that it's printed on the circuit board that you can substitute a 5y3 for a "darker" sound; but if the Sovtek is just a relabeled 5ar4, it might not make any difference in the sound.
@Justin - I also found an EH 6v6 in my stash; should I just throw it in the dumpster?

[jammo]

I know this thread is a little over a year old but wanted to clear up some details that the previous posters have not touched on. The Sovtek 5Y3's in question that put out too much voltage and can be hazardous to old amplifiers and even some new are identified by the fact that they have only 4 pins. They are actually Russian/Soviet military 5C4M tubes and might be more like a 5V4 rectifier. Some ebay hawkers say they are a sub for a 5AR4/GZ34 but the GZ34 handles 250ma current and these only 140ma.
So if your new Sovtek has 5 pins you should be OK. Also on this subject, and especially if you are in the market for a vintage GZ34, these same Russian 5C4M rectifiers were picked up by companies like Siemens and National rebranded and relabeled as GZ34s. They are easily identified by the 4 pins, round glass tops, glass smaller in diameter than the base, two support rods inbetween the plates, and a funky upper mica spacer that looks nothing like old or even new real GZ34s. There are currently two ebay sellers that are hawking these fake GZ34's and one seller from Germany even makes a claim that they were made by mullard or made in Germany on Mullard tooling, which is preposterous. Caveat Emptor - buyer beware.