[TenTec] Hercules 444 amp

Sun Aug 10 19:08:12 EDT 2014

My AL-80A is S/N 095, purchased 1 Jan 1986. It has the QSK-5 installed 
and, before that, had the older PIN-5 QSK switch, that finally bit the 
dust. I've modified the PS to be a FW bridge at 4 kV B+ so it runs only 
on 240 VAC. It still has the original 3-500Z in it and I have a spare. 
That mod required that I build a new PS in it and, because it changed 
the output impedance, alter the Pi-L output circuit for more inductance 
on 80 and 160 m in particular (I had to make a bigger toroidal inductor 
for 160 m). I added a bit to 40 m, too.

It's currently on the shelf because I got an AL-1200 for a good price, 
added a QSK-5 switch to it, replaced the filter capacitors (added 
another capacitor) and bleeder resistors and changed the HV PS to be 4 
kV (I'm a  B+ junkie). Under full load, B+ is about 3.6 kV, up about 900 
V from the original design. The AL-80A is a very nice amp and stone 
simple inside and the 3-500Z is extremely tough. At the higher B+ it 
sings very nicely and is much easier to drive, though the total output 
only increased by about 100-200 W, depending on the band.

Kim N5OP

On 8/10/2014 3:11 PM, Rick - DJ0IP / NJ0IP wrote:
> I support your opinion, Wade.
>
> My old AL-80A is only 28 years old, but has been used HARD in at least 20 or
> 30 big 48 hour contests.  When I wasn't using it, it was loaned out to
> others who were.  It is on its original 3-500zg tube and its output power
> has only dropped about 100w per band.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Wade Staggs
> Sent: Sunday, August 10, 2014 7:54 PM
> To: Discussion of Ten-Tec Equipment
> 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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-- 

Kim Elmore, Ph.D. (Adj. Assoc. Prof., OU School of Meteorology, CCM, PP 
SEL/MEL/Glider, N5OP, 2nd Class Radiotelegraph, GROL)

/"In theory there is no difference between theory and practice. But, in 
practice, there is." //-- Attributed to many people; it's so true that 
it doesn't matter who said it./