[TenTec] Centurion & Tubes

Sat Aug 4 00:22:09 EDT 2018

Rick,

Transistor amps were the future at least 10 years ago - good choice on your 
part. I and several friends have had excellent performance and service life 
with 3-500, 4CX1000A, 572B etc. Yes, occasionally one gets a lemon. A friend 
bought a NOS Eimac a few years ago - failed less than 5 days after he 
installed it.

Auf Wiedersehen,

Mike
W8TRN
----- Original Message ----- 
From: <Rick at dj0ip.de>
To: "'Discussion of Ten-Tec Equipment'" <tentec at contesting.com>
Sent: Friday, August 03, 2018 21:36
Subject: Re: [TenTec] Centurion & Tubes

>I put my 25 year old NOS into my AL-80A and let it cook for a while, then 
>slowly applied power.
> I slowly ran the output power up until about 400w out.
> It increasingly was showing a light blue inside.
> Then pop, boom, BANG.  Blew the fuse in the house.
>
> I sold the amp, and sold the tube for 20 bucks.
> Now I run a transistorized amp.
>
> 73,
> Rick, DJ0IP
> (Nr. Frankfurt, Germany)
>
> -----Original Message-----
> From: TenTec <tentec-bounces at contesting.com> On Behalf Of Stan Gammons
> Sent: 04 August 2018 04:28
> To: tentec at contesting.com
> Subject: Re: [TenTec] Centurion & Tubes
>
> Hi Bob,
>
> The 3-500 is subject to going gassy.  IF and that's a big if, I put the 
> old Eimac 3-500 in the amp (best I can read the date code on it, it was 
> made in 1979); I'll bring the amp up with a variac.  The variac I have is 
> 110/120 volts, so I'd have to re-wire the amp since it's wired for
> 220 volts.  Yes, when a tube flashes over; it's fireworks for sure!
>
>
> 73
>
> Stan
> KM4HQE
>
> On 08/03/2018 09:08 PM, Bob McGraw K4TAX wrote:
>> A comment on 3-500 type tubes.  These types of tubes have an extremely
>> high vacuum.   NOS units are subject to air leakage into the envelope
>> around the pin seals.  The coated anode in the 3-500Z and 3-500ZG
>> serves as the getter to burn the extraneous air out of the envelope.
>> It is a very incorrect belief of many hams that having the filament on
>> for a few hours will burn the air out. This is not true with this type
>> of tube thus having only the filament on serves no useful purpose.
>> The only correct way to burn the air out is to have the tube
>> operational and with enough voltage and current to cause the anode to
>> show color.   It is this heat and chemical action of the anode coating
>> that removes the extraneous air from the envelope.
>>
>> Other smaller tubes may have a getter that is ignited by external
>> microwave energy.  Once the getter is ignited, it is consumed, and any
>> leakage from that point forward will only deteriorate the tube.
>> Again, having the filament on for some hours does no good in this regard.
>>
>> External anode tubes, such as the 3CXxxx and 4CXxxx types, are
>> different designs and thus running the heater will remove any remnants
>> of air leakage as the getter is part of the cathode coating.
>>
>> If you intend to prepare a 3-500ZG or such, a filament supply, an
>> adjustable bias supply, and an adjustable HV supply, with proper
>> metering for each supply is the correct way to static burn in this
>> type tube.  The values are adjusted such that anode does show color.
>>    Just putting the tube in an amplifier and hitting the switch will
>> most likely produce a flash, bang, pop and the smoke may then exit the
>> box.
>>
>> 73
>>
>> Bob, K4TAX
>>
>>
>> On 8/3/2018 8:30 PM, Stan Gammons wrote:
>>> I think most/all of the 3-500's are made in China now.  One can still
>>> find some Eimac's that may still be good after all these years.  The
>>> near 40 year old one I have may still be good.  Need to put it in my
>>> L-4B some times and see. This is what we get for outsourcing so much
>>> of our manufacturing to China.  I've said for many years that that
>>> was a bad idea. At one time Amperex tubes were made in France.  Don't
>>> know if that's still the case.  I'm thinking no.  Maybe we can talk
>>> CPI/Eimac into making 3-500's here again? Probably not, but might be
>>> worth a try.
>>>
>>> 73
>>>
>>> Stan
>>> KM4HQE
>>>
>>>
>>> On 08/03/2018 08:12 PM, Bob McGraw K4TAX wrote:
>>>> Yes, thanks to the new tariffs we can expect tube prices to go
>>>> through the roof.   Most tubes are made in China and branded under a
>>>> US company.   a.k.a. RF Parts.
>>>>
>>>> Bob, K4TAX
>>>>
>>>>
>>>> Sent from my iPhone
>>>>
>>>>> On Aug 3, 2018, at 5:03 PM, Carter <k8vt at ameritech.net> wrote:
>>>>>
>>>>>> On 8/3/2018 4:45 PM, Greg S via TenTec wrote:
>>>>>> There will be a price increase SOON. RF Parts apparently will no
>>>>>> longer be importing Chinese tubes.
>>>>> Hmmm...bad news, as I thought China was the *only* one making
>>>>> 3-500s. If not China, who else?
>>>>>
>>>>> Carter
>>>>> K8VT
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