Considerable wisdom being spoken here.
It is quite clear that early generation ham equipment, if not home built was
certainly home repairable (and modifiable ).
Most of the better early generation solid state or hybrid transceivers used
discrete components and plug in modules. They are still home repairable.
Incidentally, there was little interest in modifying them.
Later generation all solid state rigs use large boards and many contain
devices which are now out of production and in any case repair requires
specialist skills and equipment outside the scope of most users.
While the reliabilty of present generation transceivers is impressive, I
suspect that they will be worth very little in ten years time. This will be
very much the case if the manufacturers go out of business.
Will K2 rule?
Will homebrew stage a comeback?
73
end
Barry Kirkwood PhD ZL1DD
Signal Hill Homestay
66 Cory Road
Palm Beach
Waiheke Island 1240
NEW ZEALAND
www.waiheke.co.nz/signal.htm
----- Original Message -----
From: Peter Chadwick <Peter.Chadwick@zarlink.com>
To: <W8JI@contesting.com>
Cc: amps <amps@contesting.com>
Sent: Thursday, 06 December, 2001 7:58 AM
Subject: RE: [AMPS] AL1500
>
> Tom says:
>
> >you can expect it to last dozens of years.
>
> So you can with good tubes. There are many evidences of tubes such as
klystrons
> in TV and radar service which have still met full spec after 120,000
operating
> hours. My 6L6 regulator tube still meets full spec on gm and gas, and is
older
> than Tom or I.
>
> One problem, and this applies to all components, is that when you go down
the
> road of 'cost reduction', it's very rare that something doesn't have to
give. So
> tube quality now is likely to be worse than 50 years ago, especially as
the
> market is much smaller and we expect to pay much less in real terms for
> equipment. For example, the HRO as the top line receiver cost $279 in
1936
> without tubes, power supply or speaker. How many $k is that in today's
money?
>
> An example of cost reduction is the plastic IC. Plastic IC's are fine - if
> you're careful of the environmental conditions. Large temperature ranges
and
> humidity are killers for long term reliability. Such doesn't affect
3-500s,
> though! I did once have an interesting application problem where a
guaranteed
> life of 30 minutes was needed at a chip temperature of 225 deg C...that
was in
> the drill bit of an oil well drill.
>
> One area that I am convinced is responsible for a lot of unreliability is
the
> soldered joint. Interestingly enough, I'm currently engaged on an argument
with
> a big military manufacturer on this - if he accepts the argument, it's his
> problem, so he wants to blame an integrated circuit which he's taken off
the
> board for testing and then put back, with the result that the equipment is
> working again. WW2 solder had a lower tin content than pre war, because
of
> essential material supply, and I read that even with the construction
techniques
> of those days, that had an effect on reliability. Of course, when you're
> building a piece of equipment that is likely to be shot down within 100
hours of
> operation, long term reliability isn't the aim. Similarly with glass tubes
for
> hams - how many 'operating' hours does a PA tube get? Even in a contest, I
doubt
> the tube is actually operating for 30 hours - you have to receive part of
the
> time, at least!
>
> The major overload that many tubes won't stand is being dropped! OTOH,
vibration
> on IC packages can have curious effects on bond wires in non-plastic
packages. I
> wonder what 'g' forces a 6AG7 with its metal package can withstand?
>
> There was an interesting article in the IEEE Spectrum a few years ago
about
> tubes, and how the reliability wasn't that bad once you accepted the
shorter end
> of life. There had been this outcry about tubes being the cause of the
FAA's
> computer failures, when in fact, the major problem was very old connectors
on
> very old equipment, but it was politically advantageous for the Vice
president,
> no less, to hold up a miniature tube and tell the public that the FAA were
still
> using them.
>
> The advent of microelectronics has led to major increases in complexity,
and
> hence made increased reliability a sine qua non. Nevertheless, ICs do
fail, and
> not always because of overloads. With the increasing move to custom ASICs,
I
> predict that a number of todays expensive transceivers will become
> non-maintainable items when the manufacturer's stock of ASICs runs out.
The
> chances of keeping a forty or fifty year old piece of equipment working
will go
> down enormously, especially if the ASIC happens to have a long term
reliability
> hazard built in - and sometimes, it does happen with an IC that that is
the case
> - and it shows up years later.
>
> Finally, I don't think it's accurate to say that parasitics can't or won't
kill
> tubes. There's differing opinions on how severe and how long they have to
exist
> for to do it, and I'm much more in your camp on this one.
>
>
> 73
>
>
> Peter G3RZP
>
>
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>
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