[ARC5] BC-453 B dynamotor hum

[WA5CAB at cs.com]

J,

Also, the normal ripple at the dynamotor output when running off of say a 
battery is at several hundred cps, not at 60 or 120.  It would be a whine, 
not a hum.  You need a pretty clean 28 VDC supply.  Remember that the DC 
supply also supplies the field current, and if it varies at 120 cps you will get 
120 cps ripple on the 250 VDC output.

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480

In a message dated 11/03/2015 09:06:39 AM Central Standard Time, 
aaf-radio-1 at aafradio.org writes: 
> On 11/3/2015 9:44 AM, J Mcvey via ARC5 wrote:
> >OK, it's confirmed, it's a stupid problem!!!!  I THOUGHT that I scoped 
> the DC, but when checked again, It has deep ripples, more like alternating DC 
> than DC!I jumped a 0.5 uf to ground at the B+ terminal of the output and 
> the hum volume  dropped dramatically, but there was still an unacceptable 
> 80V ripple.
> >
> >Question: What is the the ripple normally seen at the dyno output?        
>          Is there possibly a defect in the dyanamotor where there is a 
> missing winding in the armature causing the ripple?
>