Those old 30's era tubes with very low mu did not make very good SSB
linears. Even as a teenager I knew better than to use my PP 250TH AM/CW amp
on SSB after an appropriate bias change. I had a good mentor.
OTOH I did as many others and used a CE 10A or similar to drive a modified
GG 1625 to drive a few more to drive a pair of 803's on 80-20M. Bandswitch
by clip leads on the 1625's and the ubiquitous BC-375 tuning unit switch on
the 803's also in GG. I used the same BC-610 PS on the 803's as the 250TH's
and have no idea about output power or IMD but the meters wiggled properly
and I got good signal reports.
Not exactly a contesters rapid bandchanger, even the 10A used plug in coils.
My, we have come a log way!
Living on LI and a short bus/subway ride (later by car when I turned 17) to
Radio Row where cheap goodies were overflowing on to the sidewalks. The
BC-610 and other parts for the AM KW were mostly thru USAF MARS, and in NYC
the NIB 1625's were 7 for $1 and the NIB 803's $1 each.
These days I have, or had recently, 250TH's, 6C21's (run as 450TL's which is
what they were built as), HK354C's, and 304TL's in service for AM, they all
work fine with no gas problems but all are 60-70's date codes except the
354's which came out of a late 40's rig. Also used are GU-81M's and
QB5/1750's.
Linear amps here including HB are: 3-500Z's (LK-500ZC and Hunter 2000C),
8875's (MLA-2500) , 3X 8874's(Alpha 76PA), 8877 (Dentron 2000L and HB on
222mHz), 3CX1000A7 (HB on 2M), and a 8930 (AM 6155 on 432), 8122's (I have
several NCL-2000's including one on 6M). Obviously I have nothing against
ceramic tubes but neither did I have to pay much for them or the amps they
are in. The LK-500ZC gets the most and hardest use and the original 1986
Eimacs plus EBM Papst fan just keep on chugging along. I baby the 8874,
8875, and 8122 amps and the 8877 ones are surrounded by protection circuits.
The 3CX1000A7 is bullet proof and is what the 8877 should have been minus
the expensive socket.
Carl
KM1H
--------------------------------------------------
From: "Fuqua, Bill L" <wlfuqu00@uky.edu>
Sent: Saturday, January 24, 2015 11:29 AM
To: "Carl" <km1h@jeremy.qozzy.com>; "Col. Paul E. Cater"
<paulecater@gmail.com>
Cc: "Amps reflector" <amps@contesting.com>
Subject: RE: [Amps] ceramic vs glass
Naturally, there were a number of tubes that did not require fans at all,
but lost favor in the once the
3-400Z and 4-400A tube were being used in amplifiers, such as 250TH,
450TH, and the 813's. Also
still used are the 811A and 572B tubes.
73
Bill wa4lav
________________________________________
From: Amps [amps-bounces@contesting.com] on behalf of Carl
[km1h@jeremy.qozzy.com]
Sent: Saturday, January 24, 2015 11:19 AM
To: Col. Paul E. Cater
Cc: Amps reflector
Subject: Re: [Amps] ceramic vs glass
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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