[ARC5] BC-348 Dynamotor

[Michael Hanz]

The fastest way to check whether it is the armature - or something 
beyond that in the B+ chain - is to remove all four brushes and connect 
a 0-~250 volt 30mA power supply to the B+ and B- brush holder threads 
under the brush caps.  Starting at zero volts and slowly ramping it up 
will give you a systems check all the way from the brush holders, 
through the dynamotor filter pack, and all the way into the BC-348.  If 
everything comes up properly and the receiver starts working (28v also 
needed, of course), then the problem is either in the brushes (I'm 
assuming you made sure they were free) - or the armature.  If it's the 
armature, you can do a resistance check between opposite and adjacent B+ 
commutator segments then to see if you run into any anomalies.  Anything 
more than that will require a growler - an automotive electrical shop 
will have one if you get that far.

Good luck,
Mike  KC4TOS

On 1/2/2016 4:12 PM, Mark McKeown wrote:
> I appreciate all the suggestions.  I have replaced (restuffed all the 
> caps in the base of the dynamotor assembly so it shouldn't be the 
> caps.  I am running the unit on the bench using a 24 volt supply.  The 
> supply is regulated and isn't pulled down by the dynamotor.  A 
> vibratach says the unit is running at 5000 rpm which may be reasonable 
> although higher than specified.  The armature gets hot with the 
> brushes out of the high voltage end but you can still touch it.  With 
> the brushes in I get 103 volts out instead of the 226 or so 
> specified.  The entire unit gets too hot to touch when the high 
> voltage section has the brushes in it.  I disconnected the hot leads 
> from the dynamotor to the base wiring and still only get 103 volts.  
> Any more ideas? Thanks!
>

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