[ARC5] BC-454-B Dymamotor Question

[Mike Hanz]

On 1/19/2013 4:52 PM, Mark K3MSB wrote:
> I decided to refurbish the dynamotor that produced the least offensive 
> waveform and it's on the bench completely disassembled.
> C34 Across the LV contacts -- It's a square Micamold.  Is this really 
> a mica cap, or a paper cap?  It tests OK up to 600V on my IT-28,  and 
> measures around 0.001 on both my IT-28 and digital checker.  If it's 
> paper, I'd probably replace with a disc on general principle.

I agree with you.  K1LKY gave you the clue to determining its type.

> It looks like the negative winding on the LV side was completely 
> broken from the terminal screw;  I'm not sure if the dynamotor would 
> have even worked if that was the case.  I was pretty careful 
> disassembling the unit, so I don't think I yanked anything too hard.  
> Maybe it was hanging on by a few strands to begin with.   I'm now 
> using only side of the crimp connector now and I used a bit of 
> solder;  looks OK now.

Happens all the time.  You did good.

> Brushes look OK,  but the top half of the HV brushes are a reddish / 
> orange color.  I will VERY VERY lightly sand the brushes at the 
> contact points.
> Armature looks OK.

The brushes don't need sanding, but it is good policy to mark their 
locations and direction of rotation.  That will preserve the profile 
established during the run-in period.  The commutators usually benefit 
from a very light wiping with 400 grit wet/dry sandpaper, but you must 
blow out the resultant particles if you do this.

> I notice the there is nothing connected internally to the ground pin 
> on the base connector.

Take a look at Figure 8-48 in the AN/ARC-5 manual below (removed for 
qth.net recipients).  There has to be some sort of ground connection 
like that, or getting power to and from the dyno will be strangely 
problematical.  :-)

73,
  Mike