[Amps] SB220/221 - won't load on 80

R.Measures r at somis.org
Mon Nov 10 03:30:26 EST 2003



>Amp folks -
>
>I'm also working on a SB221 that belonged to my father (K6VO).  He had this 
>Amp out on his workbench for several years before he passed away in 1999.  I 
>have studied it to see what its status is - it has the parasitic suppresser 
>mods, the Harbach filter capacitor and meter boards installed.  Looks like 
>he was all done.
>
>I fired it up, no HV.  I found that the multi-meter's negative lead was not 
>connected to ground - fixed that, there is HV after all.  The Amp seemed to 
>tune up, but no power output.  The problem turned out to be a missing wire 
>to carry the RF from the load capacitor to the antenna relay.  It goes from 
>above the chasis through a hole to a lead on the relay that also has a 
>RFchoke to ground.  I can't imagine why this wire would have been removed, 
>unless it was for some planned modification.  Are there any mods that might 
>require removing this wire?

**  not  likely.  
>
>The Amp works well on all bands except 80 where it doesnt want to tune up 
>into my dummy load.  It works OK at 3.9mhz, but musters only a 100watts or 
>so at 3.5.  I see there is a 500pf capacitor added in the circuit for 80, 
>the bandswitch seems to be working OK, I doubt the capacitor would go bad, 
>but who knows.  

**  the 500pF mica  80m Load padder C sometimes shorts. 

> That's what I'll check, any other suggestions?
>
>   Dana
>
>
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