[JMS] Millen 90281 HV Power Supply

[Paul Christensen]

Thanks to a JMS list member, I now have a very nice Millen 90281 supply up
and running with a 90801 exciter.    Once a pair of NOS 816 mercury
rectifier tubes were found, they were heated for 30 minutes, then HV applied
at the lowest setting.  So far, all is well and the oil filter caps are not
shorted to their case.    I had not worked with mercury tubes in over thirty
years and had to re-familiarize myself with the start-up routine for new
mercury rectifier tubes.  

Incidentally, the big auction site has a vendor who sells low-cost,
solid-state 816 substitutes.  They appear to be a JAN type for the Signal
Corps.  Mine arrived in sealed containers.  These have not been tried in the
90281 as the 816 tube sockets require modification.  On the 816, the
filament/cathode appear on pins 1 & 4, while the cathode on the solid state
replacement is on pin 2.  It seems to me that a short jumper added between
pins 2 & 4 will allow either type of rectifier to work in the 90281 supply.

The supply does seem to be built well beyond what's needed even for high
audio duty-cycle, high-level AM.  The supply is racked up with a Lambda
model 28 and will be configured closely to N9OO's well-documented station
design layout.  

Finally, thanks to all who responded to my request.

Paul, W9AC