[Amps] SB-220

[Patrick Barthelow]

Hello Jeff,

 

First you have to locate the "spitting noise", and find the cause.  That noise is often arc over on a Tune capacitor.  (Or heaven forbid the bandswitch.)   Take a close look down into the RF Deck when that happens and you may see exactly where it is.  Try increasing loading capacitance to see if it goes away with that.  If so, just use more loading to keep circulating voltage and current in the tank down.  The spitting arc over can cause sharp edges, melt points that then become weak "launch points" for further arcover, and sometimes require burnishing to smooth out and stop the arcing.  If the arcover is on the band switch you might have more serious problems, WRT solutions.

Write with your findings of where the spitting arc is located...

Best Regards,   
73, de Pat Barthelow AA6EG

 
> From: jwill at chartermi.net
> To: amps at contesting.com
> Date: Sun, 13 Jun 2010 12:09:25 -0500
> Subject: [Amps] SB-220
> 
> Hello all,
> I just powered up a Heathkit SB-220 and I am trying to load it up on 3.770 MHz. I believe I am loading it up correctly, here are the results:
> Mode: CW
> Power into amp: 65W
> Plate current: .480
> Grid current: .180
> High Voltage (keyed): 2150
> Power out :760W (read with a bird peak reading meter)
> This seems OK on CW but when I switch to high power SSB the amp makes a "spitting"noise when I transmit.
> I am driving the amp with an Icom 761 and have the ALC hooked up from the 761 to the SB-220 and I was wondering if I needed to connect the ALC lead from the exciter to the amp if I never drive it with more than 100 watts in SSB.
> Thanks in advance, 73 Jeff KA0JW
> http://lists.contesting.com/mailman/listinfo/amps
 		 	   		  
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