[Amps] ceramic vs glass

Sat Jan 24 11:19:33 EST 2015

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 at gmail.com>
Sent: Saturday, January 24, 2015 9:40 AM
Cc: "Amps reflector" <amps at 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 at telus.net> wrote:
>
>> Date: Sat, 24 Jan 2015 12:53:21 +1030
>> From: "Leigh Turner" <invertech at frontierisp.net.au>
>> To: "'Bill Turner'" <dezrat at outlook.com>, <amps at 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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>>
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