The 160W Pd of the Chinese tubes is a fallacy many fall into atho the
Shuguan spec clearly states 125W and I dont care what RFP claims.
The last few batches appear to have thicker anodes but I stress "appear".
OTOH they also take longer to show color when pushed as an AM linear in a
Clipperton L BUT I have also been increasing the bias a bit to improve
efficiency while not showing any linearity degredation on the SA. At 350W of
carrier output for several hours of 40 and 75M ragchews (no color at that
level) the amp and tubes appear no worse for wear. Naturally the built in
fan is running at full speed when in TX.
That amp is back to the customer and is the third 4 x 572B amp Ive made that
change to, the other is a Hunter Bandit 2000B.
The next step is to see how my main amp, a LK-500ZC, responds, and then to
the Alpha 76PA when I get a chance. A NCL-2000 is also in the repair que and
the owner is into AM so that will also get a look see into what can be done.
Carl
KM1H
----- Original Message -----
From: "Jeff Blaine" <keepwalking188@yahoo.com>
I have used about 8 of the Chinese 572 specifically for torture testing in
RTTY service and I can say without qualification that the plate dissipation
limit (IIRC 160w) is not something which will keep the tube in long
service. But whipping the hell out of these tubes in AM/FM/RTTY service
with all the guns blazing is not the common application.
I would expect the current breed to give long SSB service as long as
tuning is done properly and kept to a minimum. For CW, almost as well.
From there, it goes down hill fast.
Comparing them with prior generations makes no sense because there are
virtually zero NOS old tubes remaining. You either buy the Chinese
(through some direct or distribution method) - and that is the only source
available and take what service life you can get. Or you can flip to
another tube type at some considerable amount of work and expense.
73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie
-----Original Message-----
From: L L bahr
Sent: Thursday, May 02, 2013 5:00 PM
To: amps@contesting.com
Subject: Re: [Amps] 572b
If quality control is so poor, how do you test for longevity or
robustness? Just checking the emission when new may have nothing to do
with longevity. I'd like to know how well a Chinese 572B will hold up
compared to a Cetron 572B. I wonder what short cuts the manufacturer has
taken in production when many new ones go out the door with poor emission.
What else is wrong with them? Maybe it's time for these amplifiers to be
retrofitted with other type tubes.
Lee, w0vt
----- Original Message -----
There's no doubt that the manufacturer is the problem, but since they are
the only one making them and most Ham's just need a few, a reputable
distributer is very important in the supply chain. He tests them before
selling them to be confident that they worked when they left his facility,
that is one of the reasons he is considered reputable. It costs more, but
he must becompensated for his time. A reputable dealer is paramount in
buying a tube you know has a decent chance of being good, andis the one
thing you can do anything about-choose who you buy from !! Cheers, Matt
73AD7XN
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