SB-220 Power Output Decline

[Michael A. McCarthy]

> Date:          Tue, 11 Feb 1997 11:30:55 -0600
> From:          ocker at chasind.com (Charlie Ocker)
> Reply-to:      ocker at chasind.com (Charlie Ocker)
> To:            cq-contest at tgv.com
> Subject:       SB-220 Power Output Decline

> Greetings,
> 
> I'm looking for information/advice/opinions to help me troubleshoot a SB-220 
> amp.  It's output power is declining.  When I first put it into service in late 
> November, 1996, it output a kW on 80-15.  Output on 10 was low, around 300 watts 
> max.  It served me well in the CQWW CW.  Ocassionally, the amp will emit a loud 
> POP! noise when turning on.  This POP! is an exception rather than a rule, and 
> it has happened with the tune/cw - ssb switch in either position.  History of 
> the amp is that it was built new in 1974, and has been in storage from 1985 to 
> November, 1996.
> 
> Now, I notice that the output on 20 is down to 600 watts out max.  No output on 
> 10 or 15.  Still have full kW out on 80 and 40.

   It is possible that the power supply caps have dried out.  This
is a common problem with electrolytic caps that sit for long periods
of time.  This might be causing the "pop" and the low output.
   Generally, dimminishing output power is due to either the power supply
filter caps or transformer crapping out or the tubes going soft.

73 and GL,
Mike W1NR