[AMRadio] : BC 610 needing POWER 220VAC

Rick Brashear rickbras at airmail.net
Sat Apr 8 14:39:05 EDT 2006

Sounds good to me Don, that's the only way I ever run it anyway, wide 
open.  Although I do have a variac in line it is to insure the line 
voltage doesn't get too high.  In my area it sometimes jumps as high as 
125 volts and that would do the old power tranny no good at all.  So, I 
have a line voltage monitor and variac to keep the voltage to 115 - 117 


Donald Chester wrote:

>> From: Rick Brashear <rickbras at airmail.net>
>> Well, Brian, you are right, the 11 ohm dropping resistor is only in 
>> series with the plate transformer... Of course, you're also right as 
>> is Jim that this would throw the modulation bias off... As indicated 
>> earlier, it's easy enough to operate with lower power by simply 
>> adjusting the coupling.  I say "easier" sometimes that rascal can be 
>> real touchy.
> It's best to run the BC-610 in the full power mode.  HV protect is for 
> tuning up without risking damage to the final tube or other 
> components.  Running the rig in HV protect will result in very poor 
> voltage regulation on the final, due to the series dropping resistor 
> in the HV xfmr primary.  Running it with reduced loading will throw 
> the load impedance to the modulation transformer way off, with the 
> possibility of blowing the xfmr or arcing something over in the final.
> The only proper way to reduce power would be to operate the plate 
> transformer from a variac or some other kind of autotransformer, to 
> provide a well-regulated source of reduced a.c. line voltage.  Then 
> the modulator bias would have to be reduced, but that would require 
> extensive modifications, due to the combined audio driver 
> plate/modulator bias power supply arrangement.
> Best to just run the BC-610 according to the stock instructions in the 
> manual, if you are not confident about doing extensive modifications 
> to the rig.
> Don k4kyv
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