25 Jun
2023
25 Jun
'23
5 p.m.
On Sun, Jun 25, 2023 at 5:52 PM Rob Jarratt <robert.jarratt(a)ntlworld.com> wrote:
Before I confuse matters too much I should point out that I was not using the Rainbow
power switch unit but one from a DECmate. I had erroneously thought there was a fault with
the Rainbow one. I think the fan supply may be different on the DECmate switch, so ignore
the bit about the fan turning.
It appears that there are 2 ways of powering (different types of) fans
with this power supply. Whether one was used in the Rainbow and the
other in the Decmate I know not. But anyway :
A 12V DC fan running off the DC output of the power supply. This is
the one shown in my schemtic for the supply. Note the jumper link in
the fan power plug that means the supply doesn't get mains if you
forget to plug the fan in.
A 115V AC fan connected to the unused pair of pins on the AC input
cable to the power supply (top right of the 'switch/fan assy' in my
schematc. This uses the primary winding of the startup transformer as
an autotransformer on 230V mains.
Note that the latter fan will run if the chopper side of things is
dead, the former won't.
-tony