[ARC5] BC-348 Dynamotor

[Kenneth G. Gordon]

On 2 Jan 2016 at 14:12, 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!

OK. That says to me that there are two possibilities, 1) the armature is 
damaged. If so, it will have to be rewound. You MAY find a local "motor 
shop" who can rewind it for you. Or 2) one of your restuffed caps shorted 
out.

There is an excellent motor shop in Troy, Idaho, which is a very small town, 
about 7 miles from here, so perhaps you will have one there. I have no idea 
of the cost.

Now, the second question in my mind is, "Why?". What damaged the 
armature, if it IS damaged?

There are two possibilities to my mind: 1) a component, most probably a 
bypass capacitor in the dynamotor was bad or shorted, or shorted out shortly 
after you fired it up. 2) there is a leaky or bad bypass cap in the receiver.

Dave gave an excellent procedure to check the receiver.

You have already restuffed the caps in the dynamotor, but you may wish to 
check those again, possibly with a "megger".

You may get very lucky and find that one of your restuffed caps is shorted 
out, and that the armature MAY still be good.

Ken W7EKB





Kenneth G. Gordon W7EKB

"Courage is being scared to death but saddling up anyway."--- John   Wayne