18 May
2009
18 May
'09
3:02 a.m.
Chuck Guzis wrote:
On 17 May 2009 at 21:32, Steve Stutman wrote:
The problem with the onboard regulation is that many of those original
regulators, though they might be working, are actually no longer any
good. Not sure if it's just age, or it's a lifetime of certain ones
running too near max, but in all the ones I've replaced, I've cut the
amperage draw of the board way down, sometimes in half.
If they're going to be replaced *anyway*, then makes sense just to
remove them and their associated, equally suspect tantalums/aecs
altogether. In my IMSAI, I feed each board power from a dedicated,
pluggable line running to it... ground is still done through the connector.
jS
Consider that back in the 70s linear regs like
LM309 and 7805 needed
fair overhead on the rail.
Newer LDOs by def need less.
While I can understand that using a 78xx/79xx vintage regulator might
be important for the sake of accuracy, I'd be sort tempted to use
modern monolithic switching regulators if one wanted to preserve the
S100 "on board" regulation.
No more "scorched PCB" or big honking heatsinks--and less conversion
of amps into heat.
--Chuck