[Amps] Life of tubes in ham service

Thu Dec 28 02:15:54 EST 2017

"I think" the GI-7B would be an easy tube to convert to transverse 
cooling to replace the no longer available Eimac tubes in the 
MLA-2500s.  The coolers are easily replaced by removing a single screw. 
A lathe and mill could easily build custom radiators. It'd be a simple, 
straight forward conversion.  IM products?

73, Roger (K8RI)

On 12/27/2017 Wednesday 9:59 PM, Stan Gammons wrote:
> How does one go about identifying what mfg made the Russian tubes? The 
> GI-7BT's I have have purple ceramic.  They have some marking on them, 
> but no mfg name.
>
> One of these days I'll get around to building the amp using the pair 
> of GI-7BT's...
>
>
> 73
>
> Stan
> KM4HQE
>
>
> On 12/27/2017 08:46 PM, Jim W7RY wrote:
>> They were probably Burle brand? They were famous for pink ceramic. 
>> RCA made a few too.
>>
>> 73
>> Jim W7RY
>>
>>
>>
>>
>> -----Original Message----- From: Alek Petkovic
>> Sent: Wednesday, December 27, 2017 8:42 PM
>> To: AMPS
>> 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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>>>>
>>>>
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-- 
Roger (K8RI)

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