Usually the filament volts gets 'em.
For example, here in VK6, in the old Yaesu 2100 amps, the filament
voltage is around 7% high. In the Ameritrons, it is 10% high.
Our mains typically reach 245V.
Once you get the volts back to spec, the Shuguang (Chinese) tubes are
every bit as robust as the Cetrons. Their emission is excellent. and
they are absolutely plug and play with the Cetrons. No mods or
adjustments are necessary.
Over the years, I have bought and sold over 200 of these these tubes and
to date, I've had 2 that were duds. One was cracked glass and the other,
a G-F short. I have never heard of low emission from them before.
73, Alek.
VK6APK
On 3/05/2013 6:39 AM, Jeff Blaine wrote:
Jim,
I don't know why either. Maybe I don't understand the spec or the
application or some other error. Or it could be a faster roll off in
emission at higher sustained currents. No idea. I gave up on the
tube as my goal was to build a RTTY contesting amp out of the SB200.
Eventually went with the GI7b which has been a work-horse. However,
in retrospect, I could have paid for a LOT of 572b had I not done what
ultimately turned out to be an extensive and costly conversion.
73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie
-----Original Message----- From: MU 4CX250B
Sent: Thursday, May 02, 2013 5:32 PM
To: Jeff Blaine
Cc: L L bahr ; amps@contesting.com
Subject: Re: [Amps] 572b
I'm afraid I don't understand why the plate dissipation would affect
longevity, provided the tubes have adequate cooling. Exceeding rated
grid current or plate current, or using the wrong filament voltage
could kill the tubes, as could inadequate cooling, but I don't see
why running the tubes at their rated dissipation with plenty of air
would shorten tube life, if all other tube parameters were within
specs,
73,
Jim w8zr
Sent from my iPhone
On May 2, 2013, at 4:22 PM, Jeff Blaine <keepwalking188@yahoo.com> wrote:
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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