[Amps] The quality of Chinese 811A and 572B

[DAVE WHITE]

Hi Hsu
 
I hope this helps:
 
A "good" report":
I used a pair of Chinese 572Bs in restoring a Heathkit SB200 for a friend.  They worked extremely well, gave matching currents and full output as per spec and lasted well.  These were sourced via RF Parts at the Dayton Hamvention in 1999.  The fact that they're still working and still at full output shows that they are good tubes.
 
A "bad report"
A pair of supposedly matched Chinese 3-500Zs sourced from the same supplier showed vastly different grid and plate currents at zero bias and the same HT.  We tried several sets before we found anything remotely matched.  The glass envelopes were also rather odd shapes so the air flow through cooling chimneys was uneven.  The pins in the sockets were not aligned, causing us to have to modify the sockets to take them.  The tubes seemed to glow MUCH brighter than the Eimac tubes, perhaps indicating a mis-spacing of elements internally and perhaps a thinner anode meaning that they had nowhere near 500 watts dissipation.
 
We've noticed this problem with old Soviet or Czechoslovak tubes too, but in recent years the quality of Svetlana Russian tubes seems to have increased - along with the prices which have also vastly increased too.
 
I think the problem with the 3-500Zs was one of quality control and materials - however I don't know the name of the factory that made them.  
 
Now as international e-commerce trade opens up, perhaps the manufacturers should retail directly, so the good ones can build up their good reputations.  However, they have to do this without pricing themselves out of the market - people take a chance on Chinese tubes because they are significantly cheaper than Eimac or Amperex etc.
 
I hope your friends in manufacturing find this info useful.  Feel free to contact me if I can help further.
 
Anyone else out there got feedback?
 
Kind regards
 
Dave G0OIL


--- On Fri, 14/11/08, Hsu <hsu4qro at gmail.com> wrote:

From: Hsu <hsu4qro at gmail.com>
Subject: [Amps] The quality of Chinese 811A and 572B
To: amps at contesting.com
Cc: ham_amplifiers at yahoogroups.com
Date: Friday, 14 November, 2008, 3:20 AM

Hello ,Guys!
   When I became a ham operator in 1992, I often heard some  complaint about
the quality of Chinese 811A and 572B.Yeasterday, My friend  and I  call the
manufactorer  and talk with the engineer about this, they are very surprise.As a
engineer, they seodom to  communicate with the user,due to the handicap of
language and culture etc.Some standard was different with the West.For example,
Chinese 811A's Plate dissapation only have 40W and with thin plate.If it run
60W Plate dissaption,the life will be very short.
 Well, They decide to increase the tube  quality in next year. They ask me to
send this information here, and want to hear all the complaint especialy  come
from the tube amplifier's  manufacturer  about the 811A and 572B,They want
to make good winning like Chinese 3-500Z.
  Thanks in advance!
             73!Hsu
  
  
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