[Amps] SB-220 Still testing

Gary Smith wa6fgi at sbcglobal.net
Tue Oct 16 11:51:41 EDT 2007


Rf parts house brand has a good warranty, have been told they ask no 
questions you tell no lies if one goes south..

73's,
Gary...wa6fgi

----- Original Message ----- 
From: "Darryl Kwasny" <djkwasny at yahoo.com>
To: <amps at contesting.com>
Sent: Tuesday, October 16, 2007 8:11 AM
Subject: [Amps] SB-220 Still testing


> Well, I'm slowing overcoming my problems with the SB-220. I ran both tubes 
> for several hours yesterday. With the plates disconnected. I then removed 
> one tube and connected the plate. Fired it up and got about 100ma without 
> drive. Tried driving it and the plate current would just drop to 0. 
> Checked all the mods from Rich and everything looked good. So I sat around 
> and pondered it for a while. I figured no ground to grid. Looked again and 
> was disappointed to see that there was indeed a 30 ohm grid resister. 
> Pondered some more and then checked the grid to ground. Nothing! I checked 
> right across the resister and nothing! That resister was new and not 
> smoked. It was a bad resister right out of the box. I suppose the warranty 
> from Rich is long gone. :-)
>
>  Anyway, replaced the resister this morning, popped one tube in and gave 
> it some drive, drove it a little harder and it responded will. Drove it to 
> about 250 to 300 watts out then shut it down.
>
>  Took the tube out and put the other one in the other socket. Turned the 
> amp on and it took out that grid resister. I suspected that tube might be 
> bad because of the small bang a few years ago.
>
>  Would everyone agree that the tube is belly up?
>
>  I am going to look around for new Chinese tubes. Is any one manufacture 
> any better than the others, if so which one. I am going to contact a guy 
> that gets Pentas, are they one of the preferred brands?
>  If not, which ones?
>
>  Thanks, Darryl - K5WAS
>
>
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