Since I cleaned up my workbench last weekend, and all this talk about Rohde & Schwarz PSUs with BU508A, I decided to finally pull out the NGPV 40/3 and have a look at it:
It worked a whole lot better than expected, albeit being dusty and full of nasty stickers on the front panel. 30.00 Volts set, 29.96 measured. Not too far off.
The device has a fan, but totally silent. Maybe it is temperature controlled, 10 MΩ is not exactly a heavy load.
After a few minutes however, a well known smell seeped out of the thing. Something inside seemed to rise its temperature and heat the dust.
Maybe the fan wasn't temperature controlled after all?
The ubiquitous porn shot:
Here's the fan, blowing into a heat sink tunnel.
Did the rotate-with-finger thing. Boy, that needed some torque! No motor in the single-digit watts class would turn it!
Removed the whole power transistor assembly and the fan (which actually does have some temp control; a bi-metal switch puts it into full power when the heat sink gets too hot):
At first I went to my motor department to see whether I might have something to replace it with. Of course not. It's a rather small department anyway.
There was just one thing left to dot: try to fix it.
By now you should know that I'm not the greatest friend of riveted ties, but sure as hell the brackets are riveted to the stator. Grrr.
After drilling them off, the front bracket and bearing would slide off the axle without a hitch. Holding the back bracket and turning the rotor did turn the bearing in the bracket instead of the axle in the bearing! It took quite some force to get the axle out of its bearing.
I cleaned it all with IPA and reassembled the thing. To my amazement, the motor now ran smoothly.
Putting all together again, the PSU now runs with a blowing fan and without that distinctive smell.
Now it really deserved to be de-stickerized and cleaned.
One fine day I will have to check the GPIB functionality. This PSU is not really meant to be used by the front panel controls.