I don't know where you get those numbers from but they are obviously
improperly weighted.
First of all the 3-500 fan amps far outnumber the ones with chimneys by a
huge amount,
the SB-220/221/HL-2200 alone sold in the 30-50K range according to many. Fan
failures are actually very few if the owners had enough smarts to oil the
bearings and remove the filth off the blades once in awhile. For an amp that
first sold in 1970 it has an extremely good track record
considering the abuse it gets by clueless hams.
Reports of SB-220's with filament pin solder melting can always be traced to
builder inability to read and follow directions,
or a later owner being lazy or forgetful.
The positioning of the fan blade on the shaft is critical; plus that little
aluminum top piece is critical to direct air below the
chassis....many left it off after servicing the amp. A couple of other
brands were designed by those who didn't understand air flow and created air
dams below the chassis; drilling a few 1/4" holes at the end to equalize
release solved that problem.
The Command Technologies amps are another case of an air dam frying
components; this time the PS board and components.
The AL-80 family is also a huge 3-500 seller going back 30 years and fans
arent a problem for most even at the ridiculous power the manual says is OK.
Tubes and RF components fail but not due to the fan. When manufacturers
switch to a cheap plastic fan to save money you can expect noise and quality
problems.
The Ameritrons with blowers and chimneys have their share of blower failures
or just noisy bearings that owners tolerate; the sales totals are actually
quite low so you hear little about it but there are far more active amp
forums than this very obsolete email reflector.
Something else you obviously missed is that Eimac approved in writing and
later in spec sheets the use of fan cooling as far back as the 60's for the
Johnson Thunderbolt which used 4-400A's. The stipulation was that seal
temperatures not be exceeded and Im not
aware of any 4-400, 3-400, or 3-500 that had a glass meltdown in normal
use....CB use doesn't count!
Carl
KM1H
--------------------------------------------------
From: "Col. Paul E. Cater" <paulecater@gmail.com>
Sent: Saturday, January 24, 2015 9:40 AM
Cc: "Amps reflector" <amps@contesting.com>
Subject: Re: [Amps] ceramic vs glass
I'm dubious about some of the ceramics. The ones that require more parts
to
protect it then actually use it and the old Russian jobs.
The 500Z is a time proven design. Many of the failures are do to
mechanical issues, over optimistic ops, and not the tube itself. I have
never understood why someone would build up a pair of 500s and put a
muffin
fan on them. Cheap commercial jobs do this to save money. It is really a
disservice to the tube and it's capabilities. The mean time between
failures on muffin fan types and actual blowers with chimneys on these
guys
is enormous.
Paul
WD8OSU
On Sat, Jan 24, 2015 at 9:08 AM, Jim Thomson <jim.thom@telus.net> wrote:
Date: Sat, 24 Jan 2015 12:53:21 +1030
From: "Leigh Turner" <invertech@frontierisp.net.au>
To: "'Bill Turner'" <dezrat@outlook.com>, <amps@contesting.com>
Subject: Re: [Amps] 5 Minutes for Ameritron 811H to warm up?
Personally I wholeheartedly concur with your sentiments here Bill; most
of
my shack amps are of the ceramic tube variety and indeed do seem to last
forever.
My only exception amp is the venerable Kenwood TL-922 with its nostalgic
pair of Eimac 3-500Z glass bottles...they too have proven very reliable
workhorses! The proviso rider with any tube is absence of abuse.
73
Leigh
VK5KLT
## whats the most anybody has gotten out of these russian ceramic wonder
tubes
like GU-74B etc ?? Can you get 20 years out of them, beating on em 7
days a week,
like an Eimac 3-500Z ?
## What is longest anybody has gotten out of an Eimac 8877 ??
## at least with the bigger eimac ceramic tubes, like 3x3, 3x6, 3x10,
4x5, 4x10,
they can be re-built till hell freezes over, unlike their throw away,
smaller ceramic
siblings. IMO, you get a bigger bang for the $ with the bigger ceramic
tubes, esp
since being thoriated tungsten fil, you can reduce the fil V way down,
like 12% or more,
further extending tube life. Take a 3x3... rated for 2.5 A CCS plate
current...then run it
at 1.5 to 1.7 A plate current..alon with reduced fil V. It will last
forever.
The typ 2 x 3-500Z amp is rated at 800ma max plate current.... and my L4B
runs
at 800ma..just to get 1290w po.
Jim VE7RF
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