>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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