SV: SV: SV: [AMPS] SB-220 conundrum

measures measures@vcnet.com
Fri, 21 Jan 2000 08:08:15 -0700


>Thanks Rich,and this SB 220 I repaired had been at a commercial company full
>of transmitter specialist and everybody looked for that parasitic that was
>no parasitic at all , hi! 

Parasites can usually not be found without a spectrum analyzer coupled 
loosely to the anode-resonance.  When one sends hs dits, damped ringing 
is observed at the anode's vhf resonance.  

>Just by replacing this lonely diode and its, of
>course, reservoire condenser solved the problem. No chain is stronger
>than..... etc etc. 

The best solution for the SB-220 (and TL922) is to remove 110vdc from the 
relay's bias contacts.  Also, the 100k R should be probably be connected 
across the NO contacts.  If this is not done, the filament transformer 
can be destroyed by a bad tube.  
>
thanks, Hans.

-  Rich..., 805.386.3734, www.vcnet.com/measures.  


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