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Old 10th November 2006, 10:44 PM   #1
Trout is offline Trout  United States
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Question Sovtek 5Y3 Issues

Is it me? or have a really bad batch of Sovtek 5Y3's gotten distributed to the USA.

I built 4 Fender Deluxe's this week, Bought (8) JJ6V6's, (8) JJ 12AX7's (ecc83's) and (4) Sovtek (labeled Fender) 5Y3's.

Of the 4 Sovteks, 2 have arc'd out resulting in blown fuses.

Does anyone actually make a 5Y3 that has a better than 50% mortality rate?

In each case, I pulled the tube ( less than 30 minutes total run time) Replaced it with either a Old GE, or a couple RCA's from my NOS supply and cured the problem.

I built these amps basically to spec and kept the low cap values that were used back in the 50's to 60's.

Who else or were else can I get 5Y3's not from New Sensor/Sovtek?

Trout
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Old 10th November 2006, 10:50 PM   #2
anatech is offline anatech  Canada
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Hi Gene,
I've never heard of anyone having a problem with rectifiers under normal loads. Wierd.

You're like a lightening rod for strange stuff!

-Chris
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Old 10th November 2006, 11:05 PM   #3
rdf is offline rdf  Canada
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Hi Chris, I've had my share of sparks with Sovteks too. CLC supply, first C = 18 uF followed by 10H, B+ = ~320 Vdc with under 100 ma load took out two 5AR4s. No NOS tube of various types had any issues. I wonder if Sovtek-labeled rejects are making it to these shores, the tubes were purchased locally.
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Old 10th November 2006, 11:07 PM   #4
Trout is offline Trout  United States
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haha I know,


Weird thing is the amps are perfect. The Caps are perfect, Just the *&&*(^ Rectifier tubes !

On those Sovteks, I can not find a specs sheet, But one thing for sure, They are not really 5Y3's based on voltage drop. Maybe 10V drop?

I always thought REAL 5Y3's were more like 40-50V drop. These ( when working) do not offer as much sag as I like, But there are so few sources these days I grabbed a bunch just ti get by.

The PS is wired 5Y3 ( Pin8 to 20uf-5K-20uf-22K-20uf

Im gonna post a pic of the tube.

Trout

EDIT,
Below is the photo of one of the bad tubes. This tube has less than 20 minutes use since removed from box. On the initial power up of the amp, It worked fine. I removed the tubes, Mounted the chassis in the cabinet, Installed the tubes, And POOOOF, 4th of july in a box!

Notice the center of the tube.
Click the image to open in full size.
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Old 11th November 2006, 01:52 AM   #5
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I thought a 5Y3 was a directly-heated rectifier; that looks like a cathode sleeve to me, like a big 6X4. Anyway, GE and RCA 5Y3's are relatively cheap, so why not use the good ones?
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Old 11th November 2006, 04:17 AM   #6
anatech is offline anatech  Canada
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Yes, I have my doubts about those rectifiers as well. I can accept some Sovtek failures, but not like that.

-Chris
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Old 11th November 2006, 01:17 PM   #7
Trout is offline Trout  United States
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I checked around a few musician/guitar amp forums and it appears that this is becoming a pretty common problem.

Besides the fact that they are not really 5Y3's (based on specs) the failure rate is very high.

One of these tube companies really need to step up to the plate and make a "Real" 5Y3. I am amazed that companies like Fender would be selling these in Fender Boxes with Fender Printed on the tube side by side with the Sovtek print/logo.

The only other new production 5Y3 I have seen is a ST bottle out of china. And looking at the only supplier that handled them, It appears they are no longer available.

In the guitar amp world, The 5Y3 is a important tube to run a lot of old amps as well as the hundreds of reproduction amps.

Trout
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Old 12th November 2006, 01:31 AM   #8
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I have heard about these "5Y3's" from Sovtek in this forum somewhere, and from e-mail to my web site. Many reports are similar to yours. Because of this I have not tried these tubes. I have abused several Sovtek 5AR4's (100 uF input cap and a 750 VCT transformer) with no issues. Others have had them blow up under far less extreme conditions. Either way these tubes are NOT 5Y3's regardless of what is stamped on the glass.

Most people know about the experiences that I have had with Sovtek 300B tubes. 4 failures that happened in the 4th month, right after the 90 day warantee expired. New Sensor said tough s***. These were not cheap tubes. I put the amp in the closet to be robbed for parts. About a year later I got 5 used Sovtek 300B tubes for $100, so I resurected my 300Beast P-P amp. Those tubes have been playing fine for 3 years.

My experience, and the experiences of others, points to a serious lot to lot variation in quality with their tubes. I have heard stories of some of the tubes produced during the recent mob takeover attempt being suspect also.

I refused to use Sovtek tubes for about 3 years because of my 300B issues, and I have still not put them in anything that I sell and support, although that may change. I have recently purchased a big box full of "previously auditioned" Russian tubes for $10 each. Many were Sovtek or Electro Harmonix. I have been subjecting some of these tubes to some rather extreme testing with good results so far. The long term reliability of any of them is not yet known.

I will be testing the long term effects of operation, often in excess of the specifications to determine which tubes to put in the amps that I sell, which will be adjusted to operate under normal conditions. I am compiling the data for a chart that outlines the expected power output and distortion under different operating conditions from mild to insane, and Triode or UL mode. This is going into the instruction manual for the SimpleSE which will be on my web page. Many other tubes by different manufacturers are being tested also.

I have about 8 Electro Harmonix KT88EH tubes and 2 6550EH tubes. These appear to be the same tube, and I have one of each in my amp currently. These have extra heat radiating fins welded to the plates which allow these tubes to handle more power than a conventional KT88. These tubes will dissipate 45 watts before any hint of glow appears. I have been running 2 at this level (despite protests from the power transformer) for about 3 weeks. No issues yet. Cool blue glow that dances around on the glass. All of these tubes do this at this power level. These have the best bass and make the most power of any tube tested.

I also got some Sovtek 6L6WXT's and some Electro Harmonix 6L6GC tubes. They appear to be the same tube, but they are NOT a classic 6L6GC. The plate structure is rectangular with 3 holes in each side like a KT88. These tubes can take the most abuse of any 6L6 type that I have tried including 525 volts. Again I haven't been able to blow one up yet, but I will keep trying.

I also have ONE Electro Harmonix 6CA7. Again this doesn't look like any 6CA7 that I have ever seen. For one it is a beam tetrode, not a true pentode, and it has the rectangular plate structure like their 6L6 tubes. Since I have no match for this tube I haven't tortured it much. I have a bunch of Electro Harmonix EL34's and they look like normal EL34's! They are true pentodes. I haven't tried any yet. I have some NOS american and Japanese 6CA7 tubes and they are all true pentodes. There are reports of American 6CA7's that are beam tetrodes, but I haven't seen any of them.

I have some Sovtek KT88's. They look like the old Tung Sol KT88's, and will only handle about 35 watts.

Clearly they have taken some liberty with the tube specifications on some of their tubes, and in the case of the 6L6WXT changed the name slightly to reflect the modified structure. On these tubes at least the changes seem to improve the tubes ability to handle abuse from people like me. The 5Y3 doesn't seem as successful. It must be noted that all of these tubes are from the same vintage, and because of their previous use, the bad ones may have already been weeded out. They also came from a reseller who pre-tests their tubes and puts a little blue sticker on them to aid in matching.
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Old 12th November 2006, 01:41 AM   #9
anatech is offline anatech  Canada
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Hi tubelab,
I've been running a matched set of 6CA7EH in my HF-87 for a couple years now with no trouble. A 6CA7 is a beam tetrode. EL-34 is a pentode. Anyway, the Electroharmonix are way better than the Sovteks I used to buy. The 12AX7EH and 6922EH are very quiet. Love'em. I did have one noisy 12AX7EH. But it's not worth whinning about it since I'm in Canada. Besides, one tube. I did get a mis-boxed 6L6 once, they fixed me up.

Those 6L6EH are tough! They sound great. They are, as you stated, beefier than a 6L6GC it seems, more like a 7581A I think.

The Sovtek 6L6 types are not very good. Those roll over and die when pushed a little.

-Chris
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Old 12th November 2006, 02:20 AM   #10
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alexistheo wrote:
Quote:
I thought a 5Y3 was a directly-heated rectifier; that looks like a cathode sleeve to me, like a big 6X4.
Yes, you're right. But there is a special industrial version of a 5Y3 known as a 6087. It's a GE 5-star tube that has an indirectly heated cathode and with specifications very similar to a 5Y3. I've use them and they're very nice tubes if you can find them NOS.

Perhaps the Ruskies were trying to copy these. Don't know. But years ago there were strict specifications a manufacture had to adhere to. Even down to the number you put on the tube. Since all the big U.S. plants quit making tubes, everything has changed. Now, it seems, you can build a tube however you want and call it anything you want, and no one cares.

In the words of that infamous cigar store wooden Indian (Al Gore), "there's no controlling legal authority". MUHAHAHAHAHA!!!

Victor
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