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@gmail.com> wrote:
From: Hsu <hsu4qro@gmail.com>
Subject: [Amps] The quality of Chinese 811A and 572B
To: amps@contesting.com
Cc: ham_amplifiers@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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