[Amps] Life of tubes in ham service

Wed Dec 27 21:54:20 EST 2017

Those would have been the real Svetlana who started the pink ceramic which 
RCA copied. They still use it on the GS36B/4CX400A which is a superb tube 
and Ive converted several NCL-2000's to a pair. I have no problems with 
their tubes but some others are pretty iffy.

Carl

----- Original Message ----- 
From: "Alek Petkovic" <vk6apk at bigpond.com>
To: "AMPS" <amps at contesting.com>
Sent: Wednesday, December 27, 2017 9:42 PM
Subject: Re: [Amps] Life of tubes in ham service

>
>
> On 28/12/2017 8:21 AM, Carl wrote:
>> I have used a scope to monitor filament voltage on a large number of 
>> commercial amps and have yet to see one where the filament transformer or 
>> winding does not do an excellent job of limiting inrush.
>>
>> If the HV hasnt been recapped with over 25-30 uF total that transformer 
>> or winding is also a good inrush limiter also offering switch 
>> protection..
>>
>> If spending money is of no concern then by all means buy whatever keeps 
>> you happy amd hope you do a very good job installing it..
>>
>> Any old tube, today or in the future should be brought up on a Variac to 
>> be sure it hasnt gone partially to air which will not show up initially 
>> on a glass envelope. NOS US built 3-500Z's are already becoming scarce as 
>> are 4-400A's which can often be easily adapted. The 4-250A can be used at 
>> reduced power at the same voltages as the only difference is the anode 
>> construction; the PL-175A also shows up at times as well as various 4 
>> digit numbers for the others.
>>
>> IF OK then bring the filament, plus HV up slowly to about 1200V and look 
>> for the telltale glow of outgassing. Do notkey the amp and never with RF 
>> at this stage. With amps using the old CW/SSB switch about 1800-2000V in 
>> the CW position is the norm and if the gas is not excessive it will not 
>> cause an internal arc.
>>
>> In all amps I highly suggest a HV surge, aka glitch, resistor sizeed to 
>> limit fault current to a safe level and allowing fuses or breakers to 
>> blow. A 25 Ohm 50W  Vitreous Enamel resistor is the ONLY choice I suggest 
>> (25W on SB-200, AL80's power level is fine) as it will absorb the high 
>> current without self destructing as does sand type or other cheap 
>> substitutes.
>>
>> Ceramic/metal tubes are not immune to outgassing but that is limited to a 
>> small variety...at least this year. Id be worried about Russian and 
>> Chinese offerings.
>
> The technicians at the now defunct Coastal Shipping station, VIP, here in 
> Western Australia, said that the finest 4CX250/350 type tubes they ever 
> used, were the purple ceramic Russian ones. The best life and lowest 
> leakage. At the time, they were not easy to get but they said they were 
> miles better, in all respects, that the Eimac versions.
>
> I've not had any personal experiences to confirm or dispute their 
> findings.
>
> 73, Alek.
> VK6APK
>
>
>
>
>
>
>
>> Philips and other mainline EU tubes seem excellent IMO but I havent 
>> tested enough types to be 100% sure.
>>
>> There are several ways to regetter a tube which is a different subject I 
>> have detailed many times over many decades..Perhaps someone has preserved 
>> a file.
>>
>> Carl
>> KM1H
>> Amp service since 1964
>>
>>
>> ----- Original Message ----- From: "Leigh Turner" 
>> <invertech at frontierisp.net.au>
>> To: "'Rob Atkinson'" <ranchorobbo at gmail.com>
>> Cc: "'AMPS'" <amps at contesting.com>
>> Sent: Tuesday, December 26, 2017 5:27 PM
>> Subject: Re: [Amps] Life of tubes in ham service
>>
>>
>>>
>>> Rob, I concur with your succinct sentiments here about transmitting 
>>> tubes.
>>>
>>> The only proviso I would make is the inclusion of a soft-start mechanism 
>>> on
>>> the filaments to bring them up slowly in a controlled manner at initial
>>> switch-on; and ensure the filament voltage as measured at the socket 
>>> pins is
>>> tightly within manufacturer's specification.
>>>
>>> 73
>>>
>>> Leigh
>>> VK5KLT
>>>
>>> -----Original Message-----
>>> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Rob 
>>> Atkinson
>>> Sent: Wednesday, 27 December 2017 3:45 AM
>>> To: amps at contesting.com
>>> Subject: Re: [Amps] NXP 65V LDMOS 1K80H-1800W
>>>
>>> "What happens when they quit making tubes?"
>>>
>>> For some tube types that happened decades ago.  But you can still find
>>> plenty of good 810s etc. decades later.
>>>
>>> In other words, what happens when no tube of any type is made?
>>>
>>> Answer:  Not much, except prices may go up.
>>>
>>> What happens when tubes no longer exist?
>>>
>>> Not our problem because we'll all be SK.
>>>
>>> Why are you so flippant?
>>>
>>> Because millions of tubes have been made and for ham use, a pair of
>>> 3-500Zs (to use them as an example), will outlast all of us _if they
>>> are treated properly_.
>>>
>>> That's the rub.  Broadcasters wear out tubes because they run them day
>>> and night non-stop for a year or two and they lose emission.
>>>
>>> Hams don't do that.  The only time a tube wears out in a ham rig is
>>> when hambone abuses it, usually by running too much plate current or
>>> grid current.
>>>
>>> Most common is the single 3-500 "Kilowatt amp" that pisses away 3-500s
>>> every 3 years or so.  A certain manufacturer should get a medal from
>>> the Chinese company making 3-500s these days.
>>>
>>> If you know how to run your tubes, they'll be running after you are in
>>> the ground.
>>>
>>> 73
>>>
>>> Rob
>>> K5UJ
>>> _______________________________________________
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>>> Amps at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
>>>
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>>
>>
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>
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