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Post by Edward RawdeIt usually takes a while to work out why they did it that way, and it's pretty much essential to spend that time before you start
fiddling with the circuit. That wasn't true of the guy who'd put in the 741. He was very much in the John Larkin "if it sort of
works, ship it" camp.
Which of John Larkin's products have you purchased and tested and what improvement
do you think should have been made before it was shipped?
Absolutely none of them. The timing gear he sells to the American
National Ignition Facility is based on a 1978 Hewlett Packard scheme,
written up in their journal, and it depends on starting up a 50MHz
free-running oscillator in a very predictable way.
Faster oscillators have less jitter, and while synchronising to a
continuously running faster oscillator twice may introduce extra jitter,
the net jitter on the time delay can be quite a bit less.
I had much the same problem in 1988 and went for a free-running 800MHz
oscillator.
It turns out that the first version of John's 50MHz oscillator had a
nasty - if small - sub-harmonic oscillation and he's finally found a
better version.
Post by Edward RawdeManagement liked him because he was quick. Production was less enthusiastic.
Management likely expected that problems would be found which would have to be dealt with at a later time.
I got to cleanup his mess ten years later, and only because some of the
parts he had used had gone obsolete.
It didn't mention another error - his 741 had to drive a few metres of
shielded pair, which was a big enough capacitative load to make it
oscillate, to which his solution had been to hang on a 100uF
electrolytic, so the oscillation was at too low an amplitude to be
visible. There's a standard solution for that - National Semiconductor
Applications note AN-4 Fig.14. which he should have known about.
I'd certainly had to deal with it more than ten years earlier
Post by Edward RawdeWould you be kind enough to give your opinion of John Larkin once per month instead of twice per day?
When he starts claiming to do electronic design once a month rather than twice a day.
I still don't see why it matters so much when the two of you are in different countries and, correct me if I'm wrong,
you've never used or tested any of JL's products.
One of his standard insults is to claim that his critics don't design stuff.
Post by Edward RawdeYou can't deny that JL has a successful business.
Whether his business would be more successful if he adopted different design techniques is not something I wish to go into
because it simply doesn't matter to me.
He's the electronic equivalent of a vanity publisher. He give people who
can't design their own electronics, bespoke electronic solutions to the
problems that they think they have. I did a bit of that at Nijmegen
University in the Netherlands, and most of what I found myself doing was
getting people to recognise that they had a standard problem for which
they could buy a standard solution off the shelf.
--
Bill Sloman, Sydney
