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Old 17th Jan 2019, 12:23 pm   #1
Dred007
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Default "Sony Air 7" squelch replacement

Hello,

I have a little sony air 7 radio that is working nicely.
The volume pot was defective so I have replaced it with a new one.
Unfortunately the squelch is now dead. This potentiometer is a little special as it has an auto and manual feature (pot can be both turned and pressed up and down) I am simply unable to locate the same pot or anything like it. The best I have come up with is a pot with the same resistance but it only has three pins. The original pot has 8 pins (if I remember correctly) When I solder the new pot on, the sound is dead entirely.

So for now the only way I have been able to keep the radio alive was to solder a 100k resistor to two points which seems to bypass the dead squelch and enable the volume to work independently.

Does anybody have a clue how I could use the three pin pot?
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Old 17th Jan 2019, 2:34 pm   #2
ms660
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Default Re: "Sony Air 7" squelch replacement

You can't do any switching without a switch, if an ordinary pot is your only replacement option you will have to decide which mode you prefer, Manual or Auto, for Manual short out the switch connection nearest the pot to the switches middle connection, for Auto connect the switch connection that's furthest from the pot to the switches middle connection.

The only other alternative I can think of at the moment is a separate single pole change over switch mounted somewhere if there's room, and hard wired to the volume control panel.

Lawrence.
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Old 17th Jan 2019, 5:49 pm   #3
Dred007
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Default Re: "Sony Air 7" squelch replacement

Hi ms660,

Thank you for replying to me.
This could be great! I guess I would take the manual function for more control.

Could you please take a look at this picture, I just want to be sure this is the right one i need to short. (I have put a RED box at the point where I think you refer too)
https://i.ibb.co/8DPtsD0/IMG-20190117-174347.jpg

Thank you so much for taking the time to help me.

Regards,
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Old 17th Jan 2019, 6:04 pm   #4
ms660
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Default Re: "Sony Air 7" squelch replacement

Yellow (link) for Manual.

Light Blue (link) for Auto.

And remove your added resistor.

Hopefully....

Lawrence.
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Old 17th Jan 2019, 7:22 pm   #5
ms660
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Default Re: "Sony Air 7" squelch replacement

Re: PM.....Yes, I looked at the schematic and the volume control board layout, I found the full manufactures service manual online.

Lawrence.
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Old 17th Jan 2019, 9:37 pm   #6
Goldieoldie
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Default Re: "Sony Air 7" squelch replacement

Hi
You can repair these pots
What happens is the wiper becomes detached from the plastic holder
To take the pot apart you have to file the ends off the two rods holding it all together
Carefully taking notes as you take it apart ( take pictures ! ) you will see the wiper has come loose
Clean the surfaces and scrape for the glue to work
Use a drop of super glue to hold the wiper in place and then cover with epoxy
Reassemble and use large paper clips to replace the rods
Bend over the ends or solder
Fiddly job but do able
Cheers
Pete
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Old 18th Jan 2019, 7:03 pm   #7
Dred007
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Default Re: "Sony Air 7" squelch replacement

Unfortunately, the trace was broken during the unsoldering process.
Right bollocks I made of it. I did what MS660 said but the squelch still does not work.
I tested the potentiometer and it works fine and has the correct resistance.
After tracing the PCB back with wires, the volume would not work ^^
So I had to try a bunch of weird stuff and finally with a few more trials the volume is back.
I'd probly need a resistor or something as the volume pot turns the volume up way too fast, so it does not take a lot of turning before the volume is up full. Maybe less than 1/3 turning the volume pot and the volume is blasting away.

Anyway it's working again the squelch is just on all the time now where as before it was not working at all. I guess it's a fix in a way but far from great.

Here's a picture of the mess, maybe someone will have a laugh, maybe someone will not.

https://i.ibb.co/zsnsD12/IMG-20190118-162631.jpg
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Old 18th Jan 2019, 7:09 pm   #8
G6Tanuki
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Default Re: "Sony Air 7" squelch replacement

Quote:
Originally Posted by Dred007 View Post
I'd probly need a resistor or something as the volume pot turns the volume up way too fast, so it does not take a lot of turning before the volume is up full. Maybe less than 1/3 turning the volume pot and the volume is blasting away.
That is a symptom of you using the wrong "law" for the pot. Volume-controls generally need a Logarithmic resistance-curve because this matches the human ear's perception-of-loudness.
I suspect you may have fitted a Linear pot.
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Old 18th Jan 2019, 7:52 pm   #9
ms660
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Default Re: "Sony Air 7" squelch replacement

So far as I can make out (at least) from your last photo, you've connected the volume control and the squelch control as rheostats and you've connected the wiper along with one end of the squelch control to ground via the "Manual position" switch contacts and connector CN4/1.

Lawrence.

Last edited by ms660; 18th Jan 2019 at 8:05 pm. Reason: clarification
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