25 Jun
2023
25 Jun
'23
5:06 p.m.
-----Original Message-----
From: Tony Duell <ard.p850ug1(a)gmail.com>
Sent: 25 June 2023 18:00
To: rob(a)jarratt.me.uk
Cc: General Discussion: On-Topic and Off-Topic Posts
<cctalk(a)classiccmp.org>rg>; Brent Hilpert <bhilpert(a)shaw.ca>
Subject: Re: [cctalk] Re: Rainbow H7842 PSU Fault
On Sun, Jun 25, 2023 at 5:52 PM Rob Jarratt <robert.jarratt(a)ntlworld.com>
wrote:
That is what I failed to notice and I thought that somehow there was a fault in the switch
unit.
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