[ARC5] BC-453 B dynamotor hum

[Richard Knoppow]

     You can find instructions on restoring motor-generators in some 
books on marine radio. They were very commonly used in shipboard rigs.  
The description below of undercutting the mica, etc, is very familiar.

On 11/3/2015 8:25 AM, Kenneth G. Gordon wrote:
> On 3 Nov 2015 at 11:10, Chris Bowne wrote:
>
>> I also suspect a stuck or badly worn commutator brush.  On accession I have had
>> the CW signal if my command set transmitter setup go from a normal clean note to
>> one with a buzz saw character.  A sharp "mechanical agitation" (thump) to the
>> dynamotor on the BC-456 modulator cleans things up.  Carbon/copper dust buildup
>> in the gap between the brushes and their holder causes binding and resultant
>> poor contact between the brushes and commutator.  Do you have another dyno to
>> swap in to see if the problem follows the dyno?
> For badly worn armatures, I have a document somewhere in the military
> collection here which advises turning the armature in a lathe, then
> "undercutting" the insulators which are between the segments of the
> armature. This requires a saw with a very narrow blade, and some careful
> manual manipulation.
>
> Also, that same document suggests that the brush-holders can become too
> tight for any number or reasons. Testing this requires you to check each
> brush for very easy movement into and out of the brush-holder. If there is
> even the slightest hang-up, you must either slim-down the brush, or widen
> the holder.
>
> Ken W7EKB
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL