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Author Topic: TS-950SD has RF on signal only with antenna tuner on?  (Read 1834 times)
KM4AH
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Posts: 799




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« on: April 03, 2011, 11:40:19 AM »

This rig has RF with the antenna tuner on and no RF when the antenna tuner is off. Has anybody had this problem? Any ideas? Thanks
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W8JX
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Posts: 12081




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« Reply #1 on: April 03, 2011, 12:26:10 PM »

Should not be hard to trouble shoot. Antenna is not being switched properly to bypass tuner.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
KM4AH
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Posts: 799




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« Reply #2 on: April 03, 2011, 01:06:19 PM »

It bypasses the tuner OK, the problem is when the signal is going through the tuner. Possibilities I have considered are maybe a bad shield connection on the internal coax jumper, or maybe a bad relay connection, but seems like that would be an intermittent signal rather than RF. Beats me.
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W8JX
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« Reply #3 on: April 03, 2011, 02:24:54 PM »

I misunderstood, I thought it was when you went to bypass. Those old style "coffee grinder" tuners could match a wide range of SWR's but can be troublesome when they get older. Track down a schematic and trace signal path is what I would do here.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
K8AXW
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Posts: 6357




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« Reply #4 on: April 05, 2011, 07:29:57 AM »

What kind of tuner?  What's a "coffee grinder tuner?" 

If you're talking about a simple, manual tuner, when you flip/turn a switch to bypass the tuner, the RF is fed through the ANTENNA connector to the bypass switch to the INPUT terminal.  If the tuner uses relay switching, then the relay takes the place of the switch and the bypass switch controls the relay.  Still the same simple signal path and should be easy to troubleshoot. 

An ohm meter will make it easy to find the problem.  You can also save yourself some time by cleaning the switches and or relay contacts before you start.
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W8JX
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« Reply #5 on: April 05, 2011, 07:42:07 AM »

What's a "coffee grinder tuner?" 

Thats what I call the old style tuners with servo driven variable cap/inductors in them vs newer SS ones that just use relays and banks of inductors and CAPS's.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
KM4AH
Member

Posts: 799




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« Reply #6 on: April 05, 2011, 01:49:06 PM »

Looks like luck was on my side. I unplugged and replugged all the connectors to the tuner control board. Probably had nothing to do with it, but can't hurt in a 20 year old rig. I unplugged and cleaned the coax connectors going to the tuner. RF is gone. I suspect the shield to ground connection was oxidized.

Thanks for the responses.
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