[ARC5] Dynamotors and receivers

[Mike Hanz]

On 6/9/2013 1:17 AM, Kenneth G. Gordon wrote:
> Tonight, I tested an R-25 receiver I have been working on here by powering
> it with a DM-34 dynamotor. I first cleaned then greased the dynamotor's
> bearings with that grease that Mike Hanz recommended.

If you aren't already doing so, you might want to keep the tube of 
grease wrapped up in some paper towels and a plastic sack in your 
freezer.  It has a high oil saturation compared with other greases and 
will bleed on your shelf more, especially if you keep the tube in a 
vertical position.  Lowering the temperature and laying the tube 
horizontally will reduce that tendency.  In the tiny amounts present in 
a high speed motor bearing, the separation rate is optimal for 
lubrication, according to the Mobil engineer that I talked with about 
the tendency.

> I was using clip-leads to connect everything together with. At first, there was
> some minor "crackling" noticeable in the audio, but when I connected the
> frame of the dynamotor to the chassis of the receiver with another clip-lead,
> the crackling disappeared.

Heh, heh...great minds think alike, Ken... :-)   ARC began adding a 
small pair of copper straps to the postwar receivers on diagonal shock 
mounts to accomplish essentially the same thing.  I think they began the 
practice with the R-23A in 1945, so they must have noticed the same thing.

           73,
  - Mike  KC4TOS