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Author Topic: Spastic Rx volume on ProIII  (Read 4290 times)
AF3Y
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Posts: 3793




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« on: December 14, 2012, 09:28:34 AM »


The Rx volume level on my 5 year old ProIII will just drop 80 - 90 percent rather often, and a quick tap on the key, or mic, depending on mode, with "kick it back up" to normal. The drop in volume usually happens immediately after I transmit.
The drop in Rx is not noticable in the meter, but it sure is to my ears.
I ran a query on the ProII reflector and some say it is a problem with the NR button. Beats me, but I dont like sending my Call and then not be able to hear the DX well, especially if the DX has a weak signal to start with.

No loose wires, etc.  This happens with external speaker OR with headphones.

Gene AF3Y

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KG6YV
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Posts: 514




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« Reply #1 on: December 14, 2012, 10:58:30 AM »

You probably have a loose/intermittent plug somewhere in the radio (sorry I can't guess where). 
You can choose to troubleshoot the circuitry with a scope looking for the signal line that goes bad or open up the rig and start going thru all plugs on the front panel and whatever other board contains receive circuitry.
It may also involve the transmit/receive relays in the radio (dirt, cold bad flow solder job on board).

Or, perhaps some one with a Pro III will give you a better lead. 
Or, you can take your chances and send it to an ICOM service center where they may or may not see the problem.  Even shipping the radio may vibrate the connection to completely dead or completely fixed.

The inter-module plugs on these radios sometimes go intermittent and require re-seating or cleaning/re-seating.
Flow soldered boards may have a bad joint somewhere that vibration can cause to break intermittently.

Greg
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K8AXW
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« Reply #2 on: December 14, 2012, 06:24:09 PM »

Gene:  This is a common problem, one that I've dealt with many times.  Most of the time it's a dirty control....it could be gain control or band switch or any one of the other controls on the radio.

I suggest you use the radio and the next time you notice this drop in volume tap the volume control.... twist the bandswitch and if that fails to bring the volume up, then proceed to the other controls....tapping them gently on the end of the knob. 

If you find one that corrects the problem the best thing to do is open the radio and clean all the controls with a good contact cleaner. 

One other thing that is could be is dirty antenna relay contacts, if this radio uses a relay.  Small relays can be cleaned by simply putting a small strip of paper between the contacts, then hold the relay closed with a finger or pencil and pull the strip of paper through the contacts.  Really bad cases may require contact cleaner on the paper strip.

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KA1MDA
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« Reply #3 on: December 22, 2012, 12:14:03 PM »

a quick tap on the key, or mic, depending on mode, with "kick it back up" to normal

Sounds like it could be a dirty T/R relay or something related to the T/R switching.
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AF3Y
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« Reply #4 on: December 22, 2012, 03:00:29 PM »

I decided to go ahead and put it in for repair.  When I get it back, I will advise what the problem was.

73, Gene AF3Y
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KA5IPF
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« Reply #5 on: December 23, 2012, 08:00:34 AM »

A T/R relay would cause the s-meter to drop also.

Clif
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AF3Y
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Posts: 3793




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« Reply #6 on: January 04, 2013, 02:56:59 PM »

An update....... The Rig was all OK. So....... I started looking elsewhere.

The problem turned out to be the UnUn. Replaced it, and everything seems to be OK Grin.  I spoke with Bob at Balun Designs and he thinks it may be the connector in the UnUn box. I am sending it out to him to take a look at it.

Thanks for all the replies. Next time, I'll get the dummy load out and start checking before I automatically think its the rig. Roll Eyes

73, Gene AF3Y
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