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[email protected] · October 24th 16, 08:39 AM posted to uk.transport.london

On Sat, 22 Oct 2016 18:41:57 -0500
wrote:
In article , (tim...)
wrote:
You can usually expect to get guaranteed supply for 5-7 years out of
a supplier, but more than that and you are stuck having to make
alternative arrangements. You might stretch a repair stock to 10-12
years by buying in before an item becomes obsolete, but 30 years!

And with modern electronics, the timescales get shorter and shorter.

I disagree - it depends on what components you use. If you use some specialist
flavour of the month DSP then sure, you're going to have problems down the
line (pun intended), but plenty of old components are still available. Want
a new Z80 in 2016? No problem. Ditto plenty of other kit.

So its up to the manufacturer to choose items that he can make a fair guess
will still be around in 10-20 years time and if that means using a discrete
CPU + TTL and I/O chips instead of some all in one DSP or SoC then thats what
they'll have to do. As for traction kit its not as if no one makes thyristors
any more.

Yet radios manufactured back to the mid-80s are still today installed in
train cabs and used at least until recently. A substantial cottage industry
grew up finding and repairing such radios to keep the railway going. No
doubt the same sort of thing will have to happen with the successor GSM-R
technology.

And you've rather proved my point there - if the components or suitable
substitutes weren't available then these radios wouldn't be repairable.

--
Spud

[email protected] · October 24th 16, 08:58 AM posted to uk.transport.london

In article , d () wrote:

On Sat, 22 Oct 2016 18:41:57 -0500
wrote:
In article ,
(tim...) wrote:
You can usually expect to get guaranteed supply for 5-7 years out of
a supplier, but more than that and you are stuck having to make
alternative arrangements. You might stretch a repair stock to 10-12
years by buying in before an item becomes obsolete, but 30 years!

And with modern electronics, the timescales get shorter and shorter.

I disagree - it depends on what components you use. If you use some
specialist flavour of the month DSP then sure, you're going to have
problems down the line (pun intended), but plenty of old components are
still available. Want a new Z80 in 2016? No problem. Ditto plenty of other
kit.

So its up to the manufacturer to choose items that he can make a fair
guess will still be around in 10-20 years time and if that means using a
discrete CPU + TTL and I/O chips instead of some all in one DSP or SoC
then thats what they'll have to do. As for traction kit its not as if no
one makes thyristors any more.

You completely misunderstand electronics manufacturing. Kit has only got
smaller because functions are more and more integrated into single chips.

Yet radios manufactured back to the mid-80s are still today installed in
train cabs and used at least until recently. A substantial cottage
industry grew up finding and repairing such radios to keep the railway
going. No doubt the same sort of thing will have to happen with the
successor GSM-R technology.

And you've rather proved my point there - if the components or
suitable substitutes weren't available then these radios wouldn't be
repairable.

They're repaired by cannibalisation, silly!

--
Colin Rosenstiel

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