25 Aug
2014
25 Aug
'14
3:49 p.m.
On 2014-Aug-24, at 8:56 AM, drlegendre . wrote:
Then I caught a slight whiff of "that"
smell, and switched-off, to hunt
On 2014-Aug-24, at 2:50 PM, drlegendre . wrote:
Anyway, it was getting very late, and I'd been at
it for over eight hours.
I'd accidentally swapped the +18 & -18 lines, and that was causing the
excessive current & heat.
The 8080 uses +12 & -5, both of which are derived from the +/-18 lines through
discrete zener-diode-&-series-resistor regulators.
Those regulator components may have been the source of the burning smell.
Hopefully the forward-biased zeners clamped the bad voltages and saved the 8080, but you
should ensure that those regulator components are within spec and still functioning
properly. If the regulator components got as far as burning enough to smell them, it may
be a good idea to replace them.