[Amps] Ham Tests, was Price per Watt Conversation

[Roger (K8RI)]

The problem with high power transistors is the form factor.  Typically 
you only need one with similar, but sufficient characteristics, but you 
often need to go through many to find one that will fit "if one exists".

73, Roger (K8RI)

On 4/28/2017 11:07 PM, Jim Thomson wrote:
> Date: Sat, 29 Apr 2017 02:06:08 +0000
> From: Bill Turner <dezrat at outlook.com>
> To: Amps group <amps at contesting.com>
> Subject: Re: [Amps] Ham Tests, was Price per Watt Conversation
> On Fri, 28 Apr 2017 18:36:01 -0700, K9YC wrote:
>
>> When we have to give up on a product because parts become unobtainium
>> (remember the first Ten Tec solid state amp, when Motorola discontinued
>> the devices only a year or two into production?)
> REPLY
>
> <I wouldn't worry too much about transistors becoming unobtainable
> <because equivalents will nearly always be available. Compared to
> <tubes, transistors don't have nearly as many physical variations and
> <many of the later ones will be drop-in replacements. Not so much with
> <tubes without replacing sockets and re-wiring.
>
> <In either case, where there's a will there's a way.
>
> <73, Bill W6WRT
>
> ##  tell that to my buddy, who lives 5 blocks away from me. He has
> a ten-tec hercules  SS  500 watt amp. Transistors are un obtainium.
> There is no drop in replacement either. There is no way to even re-design
> and rebuild the damned thing.   Its a door stop, worth nothing. Nobody
> has been successful in getting a TEN TEC Hercules to work.  They
> are all door stops.
>
> ##  at least with a 3-500Z amp,  you can shovel anything into it.  Like
> 3-500Z,  3-400Z,  4-400A,  4-400B, 4-400C.   I have used all 5 of those
> tubes.   Phillips  8163 will also work.  A  3CX-1200 A7  + D7  will also
> plug right into those sockets.  A  3CX-1200Z7 will also work.
> The pair of 3-500Z sockets could also be replaced with a single 8877
> socket, and new fil xfmr, plus some minor changes.
> Same B+ supply, same  plate current, same plate load Z.   Pi or PI-L output stays
> the same.   Perhaps some minor changes to values of caps on the PI tuned input.
> TR relays stay the same.  Away you go, back in business.  Heck,  you could also stuff
> a russian  GS-35B  triode in there, and it too will work.
>
> ##  Id be pissed, if the megabuck SS amp becomes obsolete, with transistors no longer
> made, or no drop in replacement for them.   Then there are other concerns, like if the amp
> company that made the amp, went out of business... like EMTRON.   What if the amp maker
> decides that the main cpu, or display board is no longer available.
>
> ##  I own 4 x drake L4B amps... only 1 which I bought brand new back in 1977.
> Replaced one bad TR relay, and one bad HV diode. One pair of 3-500Z tubes finally went
> soft..after being beat on for several hours per day...after 18 years.     Like an idiot, I sold the
> new amp to a buddy in 1979, who beat on it 7 days a week, till  I bought it back in the mid 90s.
> They just run and run.
>
> ## easy to modify and update too, like  adding vac relays for qsk, + some pwr supply mods, etc.
> Adding 160m to one is a simple task.  OEM, they also work on the 3 x warc  bands.   It will
> work on any freq from 3.2  to  30 mhz..with just some minor cap changes on the PI tuned inputs.
>
> ##  if one of em blows up.... I have 3 x spares.  Parts are interchangeable between all of em.The
> B+ supply is outboard in its own box, that was oem drake.  Called a L4PS.   I have the 4 x mating
> L4PS supplies, and any of em will plug into any of the 4 amps, since they are all identical.
>
> ##  Ok, no auto tune, who cares, I just tune one up for each band, or tune one for say 80 cw...and another
> one for 80 low ssb..and a 3rd one for  80 high ssb.   Oem, they will handle 2 kw on bypass mode.  So just
> string em all in series, nose to tail.  A simple rotary switch ensures that only one amp can be keyed at any one time.
> Key line from xcvr goes to rotary switch, with separate cables to each amp.  Simple mech interlock.
>
> ##  tubes are all interchangeable, as is any other component.   You could do the same with  2-3  SB-220s.
> Fairly easy to repair or modify a SB-220 or any other  3-500Z amp.  I would not know where to even start
> with a $7K  SS amp.   If I cant fix and maintain it myself,  I really dont want it.  Touch wood, I have had aero issues
> with the 4 x yaseu xcvrs.
>
> Jim  VE7RF
>
>
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