[TenTec] Hercules 444 amp

[Bob McGraw - K4TAX]

Based on typical usage of 3 hrs per day for 5 days per week this is 15 hrs 
per week.  The in 52 weeks this is 780 hours per year.  With a tube expected 
life of 20,000 hours,  that equates to some 26 years of tube life.

Of course someone asked me recently what I thought the average transmitting 
tube life would be.  I responded "depends on how many times they are 
abused".

Exceed grid current maximum = abused.
Exceed plate current maximum = abused.
Flashover in the PA circuit = abused.

In a properly designed and tuned amp none of the above should ever occur.

73
Bob, K4TAX


----- Original Message ----- 
From: "Wade Staggs" <tvman1954 at gmail.com>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Sunday, August 10, 2014 12:54 PM
Subject: Re: [TenTec] Hercules 444 amp


> *At least for now, even if we could afford one of the Big Gun Solid State
> Amps. I would hope that we would have the good sense to stick with an Amp
> which runs 1 or 2 of the 3-500ZG Triodes. They are as tough as Nails. How
> can you argue with a system that with proper care, will run a lifetime. 
> The
> tubes in our SB-220 are Original. This means that they are approaching
> their Fortieth Birthday. We recently replaced the Capacitors and Relay. 
> The
> Amp was still working Great when we did this Preventative Maintenance. 
> And
> Even a Cave Man with Knives and Bear Skins can repair the Amp if needed. *
> *                                                                     73
> from Wade/KJ4WS*
>
>
> On Sun, Aug 10, 2014 at 12:01 PM, Robert <rmcgraw at blomand.net> wrote:
>
>> Many to most design parameters do change radically when converting from
>> BIPOLAR to MOSFET devices.
>>
>> I seen to think MFJ does have their products in the reach of the average
>> ham.  I find typically they offer reasonable designs, reasonable quality 
>> at
>> reasonable prices. Maybe it's the hams average reach that needs 
>> adjusting.
>> The days of the SB-200 and SB-220 KIT prices are long gone.
>>
>> Good quality amps, those that are clean and don't spew garbage across the
>> bands, require good design and good quality parts.  Then add a high duty
>> cycle and it places more demand on the designs and the parts choices.
>>
>> 73
>> Bob K4TAX
>>
>> Sent from my iPhone
>>
>> > On Aug 9, 2014, at 5:38 PM, Brian Carling <bcarling at cfl.rr.com> wrote:
>> >
>> > So maybe the Hercules can be converted to use MOSFETs. Seems like it
>> should be possible.
>> >
>> > I also think MFJ needs some competition on MOSFET linear amplifiers to
>> get the price point within reach of the average ham.
>> >
>> > There is just not a good reason why so many linear amplifiers should
>> cost $3500 to $9500 when you look at the parts cost and manufacturing 
>> cost.
>> >
>> > [/SOAPBOX]
>> >
>> > Best regards - Bry Carling
>> >
>> >
>> >
>> >> On Aug 9, 2014, at 5:24 PM, Douglas <sparks06524 at yahoo.com> wrote:
>> >>
>> >>
>> >> Date: Sat, 9 Aug 2014 10:12:45 -0400
>> >> From: Brian Carling <bcarling at cfl.rr.com>
>> >> To: "k9yc at arrl.net" <k9yc at arrl.net>,
>> >> Discussion of Ten-Tec Equipment
>> >>    <tentec at contesting.com>
>> >> Subject: Re: [TenTec] Hercules 444 amp
>> >> Message-ID: <86F80EE5-1044-42AA-9641-D8859123467B at cfl.rr.com>
>> >> Content-Type: text/plain;
>> >> charset=us-ascii
>> >>
>> >> Seems like a lot of RF power transistors are similar, so it
>> >> should not be too difficult to find a substitute.
>> >>
>> >> Best regards - Bry Carling
>> >>
>> >> ------------------------------------------------------------
>> >>
>> >> Ah -  but it is hard to find a substitute. The Ten-Tec factory can't
>> find one.
>> >>
>> >> There were only a few designs of 250 to 300 watt 50V bi-polar power
>> transistors made. The remaining ones are hard to get and have an HFE that
>> is too high. Several such transistors have been totally discontinued.
>> Motorola for example is out of that business. M/AComm bought some of 
>> their
>> designs but in general bi-polar RF transistors are considered passe. RF
>> MOSFETS are now the name of the game.
>> >>
>> >> Per another poster: I've not had trouble with the power supply 
>> >> drifting
>> upward with temperature rise. Perhaps they solved that with compensation.
>> >>
>> >> 73,
>> >>
>> >> Doug/WA1TUT
>> > _______________________________________________
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