15 Nov
2004
15 Nov
'04
10:11 a.m.
"Voltage ok" may mean there's a crowbar,
or it may only mean there is
a voltage monitor. Those are very different things. Voltage monitors
I would suspect that latter, and not a particularly good monitor at that.
I've met PSUs where all the 'idiot lights' were on, but there were still
problems (excessive ripple on one of the outputs, for example).
wouldn't protect you against a regulator short.
Tore> But access to a complete array of spares if nessecary. Oh, and
Tore> the CPU is built in TTL logic, so no hard-to-get spares.
TTL is getting hard to find, especially the more obscure types such as
74S series. (And if the book says they want 74S, it's quite possible
no other variant will work...)
74S is trivial to find comparied with 74H (and yes I have found those in
classic computers) or 74L (not 74LS, of course) .Even some plain 74xxx
numbers are non-trivial to get now -- 74181 ALU, 7489 RAM, the fusible
link PROMs, 7456 and 7456 (mains - 1Hz dividers), etc, etc, etc. A look
through an old TTL databook will show a few dozen devices you'll no
longer see in the catalogues.
-tony