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Author Topic: SB-200  (Read 656 times)
W3HD
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Posts: 23




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« on: October 25, 2007, 01:28:36 AM »

Their is a bypass switch on my SB-200, when I turn it on my S meter drops, turn it off S meter goes up, sometimes my RX goes down to nothing
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KA5N
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Posts: 4380




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« Reply #1 on: October 25, 2007, 02:36:04 AM »

The SB-200 didn't come with a "by-pass switch" so it must be a mod of some sort.  I can only guess as to its function.  From the description of the complaint, the switch or an associated relay must be dirty.  So many mods are ill-conceived, poorly executed, or just plain wrong.  About the only mod that makes any sense on the SB200 is a standby switch which prevents the amp from being keyed while the power is on.  Without knowing more about this switch I can't give more help.  Probably the mod isn't needed and would be best removed.
Allen
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W3HD
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Posts: 23




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« Reply #2 on: October 25, 2007, 04:17:55 AM »

Thank You
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N3JBH
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« Reply #3 on: October 25, 2007, 04:42:31 AM »

While my experience with the SB-200 stand by modification is rather limited.
The only mod I know of is really a rather simple one that involves the use of a spst type switch wired in series with the keying line. If this is the case it would be a relatively easy and straight forward mod to trace and remove to trouble shoot.  Jeff
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KI4NX
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Posts: 121




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« Reply #4 on: October 25, 2007, 10:08:46 AM »

The mod of the SB-200 with a push-pull switch became the SB-201. The switch is on the variable resistor controlling the sensitivity of the SWR meter. When you pull it out the amp was effectively off. When you pushed it in, the amp would activate the relay upon transmit.  If the switch is wired wrong, as has been stated, anything is possible.

Ken
KZ4y
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W1QJ
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Posts: 1438




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« Reply #5 on: October 25, 2007, 04:28:09 PM »

What is happening is this, when you switch that "added switch" the antenna relay is being engaged which is taking the antenna out of the circuit and ready to except power from the transmitter.  The way it is working tells me it was not intended to be a bypass switch but rather a manual transmit switch.  The reason most likely being that the Sb-200 has a 120vdc antenna relay and a solid state modern transciever can not switch that so the guy put in a manual TR switch (like in the olden days)He did not want to spend the money for a soft key mod or wanted to build his own.  You need to address the 'soft key" issue at some point anyway.  But I can tell you it is NOT a bypass switch, it is a manual TR switch as it is working.  Lou
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KE3WD
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Posts: 5694




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« Reply #6 on: October 26, 2007, 09:44:10 AM »

Not being able to examine the amp and that switch circuit, I'm not going to even try to tell you explicitly what that added switch is really doing in there or how it is wired.  (!)  

*Might* be switching the relay, might not, we have no way of knowing from here.  

The only surefire solution would be tracing the circuit and maybe even drawing it out.  

Logically, it should most likely be switching the relay coil, but there exists the possibility of some kludge installed by someone somewhere...


KE3WD
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WU6X
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Posts: 12




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« Reply #7 on: November 02, 2007, 05:05:23 PM »

I had the same problem with keying the my SB200 with my new FT-857D. Solved it by adding an external relay. See my post on the Digital section of this forum.
73,
WU6X
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