[time-nuts] Re: HP Z3801A project update

[ed breya]

The new boost converter is working great for external DC power input. 
Yesterday I put the Z3801A guts back into the carcass, after being out 
of commission since October when I started the latest round of additions 
and changes. The bench supply I've been using doesn't have enough oomph 
to do cold start (fold-back trips at about 3 A), but another, heavier, 
fixed output one works just fine. Once thoroughly warmed up, at room 
temperature, the Z3801A is running well and quite efficiently.

With 13.6 V, 1.8 A external input, it's about 24.5 W in, making 24 V, 
which is running the Z3801A, the two fans, and the 12 V converter that 
powers all the peripherals like the digital clock (in dim mode, when AC 
is off - forcing to normal brightness adds about 120 mA load to the 
external source), control circuitry, and indicators. Considering the 
boost converter's best case overall efficiency may be around 90 percent, 
that means only 22 W or less is running the whole works. The hand-off 
works great too, in both directions. Line power and external DC can now 
back each other up without a hiccup.

Ed