[AMRadio] BC1-J Mod trans. is fine.

[Donald Chester]

>From: KC4QLP at aol.com

>also be sure the transmitter chassis is grounded...and that you have the
>chassis of your modulation transformer well grounded/connected to the 
>chassis
>of the transmitter.I've seen in commerical installs where some dummy had 
>left
>the transformer just sitting on the floor of the transmitter,not bolted
>down..and with every modulation peak there would be a small arc from the
>metal feet of the transformer to the grounded chassis of the transmitter.
>I'm surprised it didnt whipe out the mod transformer in that case.
>
>Bob Carter
>  Operations/Engineering

Better still, mount the entire transformer on good insulation.  Why put 
unnecessary high voltage stress on the insulating material in a transformer, 
especially if it is 50+ years old?  If the frame of the transformer is 
grounded, you have full DC potential  between the core and the winding, and 
the only thing standing between the two is the insulating material, often 
nothing more than plain old paper, maybe impregnated with wax when the 
transformer was built back before WWII. If the entire thing is floating, 
then the core/frame is going to pretty much climb to high voltage DC 
potential, due to the "capacitor" consisting of the winding, insulation and 
core.  The spark you noticed from the transformer sitting loosly in the 
cabinet floor was due to capacitive discharge.

Just treat the transformer as if the entire thing was strapped to the +HV 
lead.  It might not hurt to attach a warning label.  You wouldn't want some 
unsuspecting soul to have one hand on the transformer case and the other to 
ground, just at the moment when the old paper insulation decids to let go!

I float all my HV filter chokes, modulation transformers and modulation 
reactors above ground.  There is simply no good reason to subject the 
internal insulation to that additional high voltage stress.

Don K4KYV

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