I wonder how long ago those RF Parts 3-500Zs were manufactured. RF Parts, on
their website, acknowledges quality control issues that existed several
years ago, but claims to have narrowed their sources while "helping" to
improve quality control at the currently favored factory. The 3-500ZGs I
recently obtained from RF Parts are performing well in my Drake L-7. While I
haven't measured individual parameters, a close visual inspection at
installation time found no trace of the reportedly obvious poorly centered
elements, plate caps, pins, and imperfect glass, etc. that seem to have
plagued earlier batches, as reported elsewhere and acknowledged by RF Parts.
Your mileage may vary, but for what it's worth, mine have been just fine.
Chuck, N4NM
----- Original Message -----
From: "DAVE WHITE" <mausoptik@btinternet.com>
To: <amps@contesting.com>; "Hsu" <hsu4qro@gmail.com>
Sent: Friday, November 14, 2008 5:15 AM
Subject: Re: [Amps] The quality of Chinese 811A and 572B
> 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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