[Amps] SB-220 saga continues

[W7RY]

Sounds like the relay in the amp is energizing when you turn on the amp. My guess is that your relay contacts in your transceiver are stuck (shorted). 

Unplug the PTT cable from the amp or the rig. I but it works fine then. If so, you need to repair your rig. AND add a PTT buffer between the amp and the rig so it does not happen again.

The PTT line of the SB220 has a .01 or .02 uF cap across the plug. When the transceiver keys the amp, the relay in the rig must short out the .02 uF cap and this causes a pretty big arc across the relay contacts of the rig. 

73

Jim W7RY

  ----- Original Message ----- 
  From: Alfred Frugoli 
  To: amps at contesting.com ; YCCC 
  Sent: Saturday, November 08, 2008 8:23 PM
  Subject: [Amps] SB-220 saga continues


  Hello everyone,

  So it seems I've got a problem with my SB-220.

  When the amp is off, but connected in the RF path, everything is fine.

  When I switch the amp on I've suddenly got lots of attenuation happening on
  the receive path.  Transmit seems fine - amp tunes OK etc.

  My first suspicion was that there were dirty relay contacts on the receive
  side.  Cleaned the contacts with no success.  Then I realized that the
  problem only occurs when the amp is on.  So a trip to the schematic tells me
  I don't understand.  In the RX mode the RF path through the amplifier should
  be the same as when the power is on.  So I'm not sure where my attenuation
  is coming from.

  Just testing it a few minutes ago I can make an S5-7 station almost
  completely disappear by turning on the amp, so I've got somewhere in the
  area of 20db of attenuation happening!

  Thoughts?

  Thanks.

  73 de Al, KE1FO

  -----
  Visit my amateur radio contesting blog at ke1fo.wordpress.com.
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