If some of the UK tuners actually do work and others
don't or the ones that do work are prone to quit, it really
could be both bad design and poor quality control. Le'ts say
that the phase lock loop which is at the heart of almost all
modern tuners for AM and FM uses circuitry that is being run at
something near its design limits so that a very small change in
value of one of the components causes the loop not to lock any
longer.
That is potentially bad design because of the following:
No matter where you live, the real world rules. We have
humidity, temperature and dust and all those things can effect
certain components.
If the circuitry goes out of spec due to one or more of
those components changing slightly, it quits working. Since
everything must be top notch, any slight variation in one or
more parts means that your tuner may quit which is related to
quality control. In this case, the real world parts that are
available may not be up to this job so poor design begets
quality control issues since you are asking for an almost
impossible level of perfection in finding parts good enough for
the circuit.
I have no actual knowledge of the phase-lock loops used
in this tuner, but I have actually built circuits with
phase-lock loop IC's and they are excellent devices until you
start to run them near their upper frequency limits at which
time they get flaky.
If you can tweak and tune on a work bench to make the
circuit work, but it quits after some of the parts age slightly
or the room gets a little cold or hot, it's never going to work
reliably.
Let's hope they come to their senses and design
something that keeps working even if it rains during the first
quarter of the Moon. I am joking, but one does sometimes run in
to designs that aren't very fit for the real world and its
slings and arrows.
I hope you had a happy Christmas and may your new year
bring phase-lock loops that lock and track properly.
Gordon's description of what the PLL's do is spot on.
The circuits I built with them were not frequency synthesizers,
but FM detectors. Those also have several factors that must be
tweaked to get proper operation. It's a fine line between
decoding a clear signal and loosing tracking which makes the
loop never really work at all.
Martin
"Mrs. Lynnette Annabel Smith" writes:
> Hello Dane
>
> I think you're missing the point. I never said it was quality control, it
> is a design flaw as I said in my first post. A design flaw is very
> different to quality control.
>
> The design flaw is an issue whereby some models, (they've only seen it in
> UK models so far), develop a fault on the tuner's phase lock loop
> circuitry (whatever that is), and the PLL cannot synchronise. Gordon is
> telling me that the PLL is an IC which stabilises the base frequency of
> the tuner so that the multipliers function properly. Well I don't pretend
> to understand, but there you go. Apparently there is an intermittent
> design flaw somewhere in that lot which is causing the tuners to
> basically go AWOL and refuse to tune. It isn't anything remotely to do
> with quality control, whatever name you want to give it, (Or rather,
> Martin does). :)
>
> Merry Christmas all
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