I didn't mention any numbers. If I did I would have pulled them out my
butt like most do. I really don't know where you would find any reliable
data on it other then peoples experience and hearsay. Duty cycle plays the
most important role in all of this.
My sole point was, tubes properly cooled last way longer in full tilt buggy
then those that are not. The muffin fan jobs you mention and specifically
the SBs are not rated anywhere near the tubes capability. Niether is the
P/S for that matter.
Having used both types at many MARS stations and myself, we opted for
something that used chimneys as we did not have to replace the tubes. More
money initially but not popping bottles in and out. I was sitting here
trying to recall if I ever replaced a 500z in a top end amp, ie Henry. or
whomever. I do recall putting them in muffin fan decks often.
Nope, didn't look up the spec sheet. Last time I looked at one cooling was
stated verses usage with minimums. I'll have a look.
So, my opinion and experience speaking and nothing else.
Paul
WD8OSU
On Sat, Jan 24, 2015 at 11:19 AM, Carl <km1h@jeremy.qozzy.com> wrote:
> 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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>>>
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