20 Jul
2020
20 Jul
'20
3:03 p.m.
On 07/20/2020 07:00 AM, Peter Coghlan via cctalk wrote:
I have a MicroVAX 3100 which has a H7822 power supply.
The power supply
and the machine itself mostly work (there is a problem with the SCSI
interfaces but that's another story) except that the two fans in the
power supply don't run. If left on for a long time, the machine gets
too hot and a thermal trip operates, shutting it down.
The fans are DC 12V 0.2A and if I connect them to +5V or +12V, they
work fine and don't draw excessive current so there would seem to be
a problem with the section of the power supply which drives the fans.
Unfortunately, it's operation is not obvious and the power supply is
a pig to work on.
Yes, it probably has a temperature sensor and a fan speed
controller. If you don't care about noise, you
could probably just rewire the fans to 12 V directly.
Jon