[AMPS] TS940S CONNECTION TO HEATHKIT SB200 LINEAR

[measures]

>At 10:29 AM 10/20/1999 -0700, measures wrote:
>>
>>>
>>>Hi Bill.  Have a TS-940S and just wired up an amp a
>>>few days ago.   
>>
>>€  The TS-930s has a hv npn transistor that keys the amplifier - without 
>>the delay caused by a relay.  The TS-940s uses a relay.   The relay will 
>>cause hot switching in any high-speed switching amplifier.  The article 
>>about the TS-440s on my Website shows a circuit that replaces the pokey 
>>amplifier control relay in a 440 or 940 with a 300v npn transistor.  
>>Total cost is around 50-cents.  
>
>This is part of the story.  Actually, the TS-930 can switch that line with
>either a transistor or a relay, depending on a jumper setting inside the
>radio.  However, the transistor switch in the 930 is not rated to handle
>handle the SB-200 relay voltage or current - I think it's 60V/50 ma. or
>some such thing. 
 
Way worse news than that.  The supply is Negative, which is Shortsville 
for npn transistors.  As I recall, the npn transistor in the 930 has a 
200v rating.  .  

> .   I'm guessing the 940 is similar.  I was also warned
>against trying to switch my SB-220 with the relay, without a series
>current-limiting resistor.

True enough.  The SB-220 RL control line has a c. .0.02uF-GMVcap / 03uF 
cap across the jack.  Every time one transmits, the relay in the radio 
shorts out 120v of charge on the cap.  This eats contacts.  Adding 100 - 
200 ohms saves contacts.  
>
>For an SB-200, I suspect you get hot switching regardless of how fast or
>slow the transceiver is...

Not if you have a TS-820S.  
>
cheers,  Pete


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


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