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Author Topic: Yaesu 757gxii speech processor issue  (Read 1615 times)
KD0OCY
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Posts: 17




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« on: December 27, 2012, 08:35:46 PM »

At first, I noticed that I was not getting any power out on ssb and I thought... Oh no! I've finally done it! I blew a final!  Then I tested it with other modes.  CW, AM and FM all worked (or at least put out the full 100 watts power into my dummy load). Then I narrows it down to my processor button.  Turning the processor button to the off position allowed me to put out full power in ssb.  I was experimenting with a mixer running through the RCA phone input (monitoring my ALC levels and adjusting settings to produce a clean signal) when it happened which I assume might have contributed to my problems.  I am trying to find out why I can put out full power without the processor but when I turn the processor on ssb puts out nothing. Any insight would be appreciated.
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KA4POL
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Posts: 2028




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« Reply #1 on: December 28, 2012, 02:03:30 AM »

You would need to check out the signal path. You might have destroyed some part of the processor section.
If you don't have measuring equipment I advise against doing this yourself.
You also can find support in the 757 Yahoo group.
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N4NYY
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Posts: 4799




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« Reply #2 on: December 28, 2012, 04:02:15 PM »

You would need to check out the signal path. You might have destroyed some part of the processor section.
If you don't have measuring equipment I advise against doing this yourself.
You also can find support in the 757 Yahoo group.

I hit more 100W peaks with the processor on on my FT-950 (narrow for DX). When I turn the processor off (for rag chew in wide mode), my peak are much less. Is his 757 putting out no power with the processor off?
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KD0OCY
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Posts: 17




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« Reply #3 on: December 28, 2012, 07:17:02 PM »

Thanks for responses! To clarify...

Processor on = no power on ssb.

Processor off = normal ssb power output.
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KE3WD
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Posts: 5689




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« Reply #4 on: December 28, 2012, 08:01:00 PM »

Thanks for responses! To clarify...

Processor on = no power on ssb.

Processor off = normal ssb power output.

Which = Something blown in the processing circuitry. 


73
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KA4POL
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Posts: 2028




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« Reply #5 on: December 28, 2012, 11:20:12 PM »


Which = Something blown in the processing circuitry. 

73

That is why I suggested to check out the processor circuitry. A DVM would be the minimum approach, better of course would be using an oscilloscope.
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KE3WD
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« Reply #6 on: December 29, 2012, 09:10:11 AM »

... I was experimenting with a mixer running through the RCA phone input (monitoring my ALC levels and adjusting settings to produce a clean signal) when it happened which I assume might have contributed to my problems. ...

There's a safe assumption <grin>

Also tells me that the problem is likely at or near the Input of the speech processor circuit.

You likely shoved a ~1.2 - 2V AC Line Level signal through a ~50milliVolt or so Mic input.  That would certainly be inappropriate and could blow something active in the circuitry back to the sand from which it came. 

 First place to check.


73
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KD0OCY
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« Reply #7 on: December 31, 2012, 07:53:30 AM »


There's a safe assumption <grin>

Also tells me that the problem is likely at or near the Input of the speech processor circuit.

You likely shoved a ~1.2 - 2V AC Line Level signal through a ~50milliVolt or so Mic input.  That would certainly be inappropriate and could blow something active in the circuitry back to the sand from which it came. 

 First place to check.


73

I was aware that something like that could happen. I was having a lot of trouble getting my ALC to do what I wanted and it would have been fine if I realized I had my processor on.   Thanks for confirming what the issue is. You've all been very helpful.
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KD0OCY
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« Reply #8 on: December 31, 2012, 06:15:58 PM »

Thought I would let everyone know it was even lesser of a deal than I imagined. Somehow (probably while I was plugging things and unplugging from the back) the compressor setting was turned all the way down.  Now it appears that my processor works. Thanks for the input though. Glad I didn't have to replace anything.
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KA4POL
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« Reply #9 on: December 31, 2012, 11:06:56 PM »

Good to hear that. And you have made some experience as well. Check the easy things first and don't panic  Cool
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