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Chinese 572B tubes and RF Parts

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J. Aaron Holmes

Sat Mar 03 2007, 08:44AM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

!grr

Well, I suppose the end of this story can be guessed from the title, but I'll admit I'm still having a hard time believing it. Anyway, I ordered a matched trio of Chinese-made 572B tubes from RF Parts, as they seemed like good "beginner" tubes to play with (intended on using two and keeping one for a backup). Anyway, they got here today, and straight out of the box I found a number of problems: One tube had a very significant crack around the grid lead seal in the base. It was very plain to see, and were it not for the metal it was wrapped around, a large piece of glass would probably have been jingling around in the bottom of the tube. A second tube had a misaligned metal plate on one of the grid posts that was so far bent down that it was within an eighth of an inch of the tube plate. Seemed like a great place for arcing. I'll have to dig out the camera and take some good photos of these, but they just look like j-u-n-k, period.

In any event, the tubes will be heading back to RF Parts next week. I haven't decided whether I'll bless them with my business again, or if I'll take my business of replacing the tubes to somebody else. If I bother to pay for new tubes again, I'll probably buy the Svetlana 572B's or go NOS on eBay.

So there you have it. Think twice about buying Chinese-made tubes, or at least the Sino/Shuguang 572B's. I know some of you have used the Chinese "Taylor" 833-A and -C tubes without trouble, though. I guess they must be ok.

Grumble, grumble...
Aaron, N7OE

Sulaiman

Sat Mar 03 2007, 11:21AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Could it be that the breakage and internal mis-alignment are due postal damage?

If subject to impact the internal parts could have moved.

(I have seen equipment that looks perfect on the outside with major internal damage due to shipping mis-handling)

Dr. Drone

Sat Mar 03 2007, 04:18PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
Location:
Posts: 1673

J. Aaron Holmes

Sat Mar 03 2007, 06:09PM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

I suppose it's possible that the cracked grid lead seal could have been shipping-related, but it's only the inside half of the seal that's cracked, so it's pretty wierd. The tilted metal on the grid support is welded in place. It was almost certainly that way straight from the factory. That is the one that bothers me the most.

These pictures turned out HORRIBLE. Positively awful. But they'll give some idea of what I'm talking about. I really should have used my video camera instead, since it seems to be able to focus at much smaller distances:
http://silicon-arcana.com/tubes/cracked_grid_lead_seal.jpg
http://silicon-arcana.com/tubes/bad_grid_post_plate.jpg

I read the Chinese tube reviews on eHam.net before buying these, and felt pretty good about ordering them. There aren't any reviews of the 833's on there, but the 3-500Z and 572B clones scored well. I actually have a Chinese-made 3-500Z clone, and it looks as good as any Eimac tube I've ever seen. The 572B's just look like a lot of corner-cutting was taken at the factory. I'm not impressed at all by their appearance. I'm totally willing to believe other Chinese tubes are different though.

It's a bummer, as I'd pretty much gathered everything else needed to make a nice 572B coil, so I probably will go ahead and get the Svetlanas or find something NOS.

Regards,
Aaron, N7OE

Terry Fritz

Sun Mar 04 2007, 02:38AM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Hi,

If you think they just look bad, for goodness sake don't plug them in or you will "really" find out how bad they are!

My tube coil came with Chinese tubes (811). After I glued both top caps back on and also glued one back into the base (they "rattled apart" in the mail

) they lasted about 15 seconds... One had two internal wires to the pins miss routed too close and shorted with a dramatic bang... The other had a miss formed glass part in the base which probably would have failed in another 5 seconds.

I replaced them with Svetlana types. The new Svetlana tubes are approximately 10,000,000 times better

Rock solid, very high quality, and zero problems...

So tell RFParts you want Svetlana "only"... Yes, they are the most expensive, but not too much more... I would have a hard time believing the Chinese tubes I have seen would ever run for any length of time and I doubt they are even tested... The quality is unbelievably poor... I don't even know why they bother to try to make tubes... A lot of stuff from China is really nice, but they don't do "tubes"... I almost doubt if they even know what they are supposed to be used for... It's like they made a cheap "visual" copy from a picture or something...

So just get the Svetlana and be happy. You won't need extras unless you break it or turn the coil up way too high... They should last forever...

Cheers

Terry

...

Sun Mar 04 2007, 02:58AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

I haven't really had any trouble with RF parts, but in general the chinese 811a tubes are crap compared to the nos design. The biggest problem I have is with the internal wire that goes to the gird gets close to the filament and then arks over... But in general the plates can only handle a fraction of the power a 'real; 811a can.

"You get what you pay for"

J. Aaron Holmes

Sun Mar 04 2007, 03:01AM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

Hehehhehe... Terry, your reply makes getting busted tubes almost worth it

LOL!! "Cheap visual copy from a photo". I love it! I think the quality definitely varies though, as I have a Chinese 3-500ZG that looks fantastic (rebranded "RF Parts", although I got it at a flea market). That particular Chinese tube has rated well on various ham sites, too. But from what I've lately read, it seems the Chinese have been making some of these tubes a lot longer than others. The 572B appears to be a relatively "new" thing. Still, just the look of these is pretty inexcusable. I suppose the most disappointing thing is that RF Parts would sell them, since they're generally regarded as a pretty good business.

A coworker of mine built a VTTC a few years ago using two of the Svetlana 572B's. Despite that hams love to complain about them because they're electrically different from the Taylor clones, he runs them with a level-shifted MOT and they haven't flashed over; they're seeing like 15kV from the tank ringing and they're only rated for 2.5kV! I was pretty impressed. Stupid me for not just buying a pair of *those*.

I'm torn now between the desire to complete my 572B-based design and the desire to get some 3-500 and 3-1000 sockets. The 3-1000Z sitting on my desk has the most wonderfully symmetrical structure inside, its draw has increased substantially after seeing these Chinese 572B's. Yikes!! Still, I could buy a nice pair of Svetlana 572B's or I could spend the same money on a 3-1000 socket, so probably I'd be stupid to do the latter

) (but I've done stupider things before, like what this thread is about...)

Regards,
Aaron, N7OE

Steve Conner

Sun Mar 04 2007, 11:43AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I like to play with tube audio. I've bought quite a few Russian military tubes, and even some brand new Russian designs specially for audio, but I've not tried Chinese tubes, and I wouldn't really care to either, from what I've heard. The Russian stuff seems to be pretty good.

Another interesting tube maker is JJ, started by a guy who bought out the old Tesla tube plant in the Czech Republic. He has a great reputation for quality. I think he only makes smallish audio tubes though.

Speaking of which, maybe those Chinese 572Bs were made for audiophool duty

They only need to be visual clones, since tubes always sound about as good as they look :P

There's a guy over here who brings a tube coil powered by a Svetlana 572B to most of the teslathons. I've seen him smoke a lot of components on it, but never the tube.

I have a 4-400A with socket and filament transformer, pulled from an old induction heater, that I keep meaning to do "something" with :/

J. Aaron Holmes

Sun Mar 04 2007, 10:26PM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

Steve Conner wrote ...

Another interesting tube maker is JJ, started by a guy who bought out the old Tesla tube plant in the Czech Republic. He has a great reputation for quality. I think he only makes smallish audio tubes though.

Yeah, nothing too big listed on the web page. You could probably get a spark by sticking boatloads of those ~450V tubes in parallel, though

Call it a "MMT" (Multi Mini Tube) coil

A "hollow state" relative of the OLTC. OLVTTC? At 5V on the filament, you could just series 48 of them to avoid the need for a filament transformer, hehehehehehhh...

EDIT: In fact, THIS should be a contest: Who can get *any* sparks from an OLVTTC

(48 300B's with filaments in series and plates in parallel would have to do *something*, I think!)

Regards,
Aaron, N7OE

J. Aaron Holmes

Mon Mar 05 2007, 08:13PM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

(Followup - sorry for the double-post)

I talked to a guy at RF Parts this morning. He seemed eager to remedy any issue I had with the tubes, which was nice. Also, he confessed, they actually hadn't sent me a matched set despite my having ordered one. Doh!

I told him I blamed their online ordering system, which is pretty ambiguous in its treatment of matched parts. Basically, I could specify either "3 matched 572B's", or "1 572B-M3", since they have part numbers for the matched sets, yet they also have a "Matched" checkbox on the order form next to the quantity field. Wierd. Since their ordering example used the former approach, that's what I did, however now you may all learn from my experience

In exchange for my trouble, I was offered an "upgrade" to the Taylor-branded tubes, which the guy insisted had a great reputation and were not only more aesthetically-pleasing, but also more rigorously hi-pot tested. Basically, they're the "top pick" Chinese tubes and come from a different factory. Hmmm... The other thing he told me was that the Svetlana 572B's were out of production, and would soon be gone forever

...so I'm not sure what I'll do. The tubes I ordered are on their way back. Now I'm torn between the desire to get the Svetlanas and own a bit of history (for about $60 more for the set) and the desire to validate the use of a current-production tube in a VTTC. What to do, what to do? The latter would seem to have more value for the VTTC'ing community, however I'm not especially eager to go through this again. Hmmm...

Regards,
Aaron, N7OE

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