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Old 20th Jan 2020, 6:53 pm   #1
Final anode
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Default JRC JST-135 Vfo knob removal

Hi
I am taking off the front to change some of the tact switches on my JST-135, does anyone know the hex key size for the VFO knob, 1.5mm seems a loose fit and I wouldn't have thought it was 1/16, don't want to risk breaking it.
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Old 20th Jan 2020, 9:04 pm   #2
g4aaw pete
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Default Re: JRC JST-135 Vfo knob removal

Hello Dave

I don't have the definitive answer, but:

Kenwood TS830 = 2mm
Kenwood R5000 = 1.5mm

just as a point of reference!
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Old 20th Jan 2020, 11:01 pm   #3
Final anode
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Default Re: JRC JST-135 Vfo knob removal

1.5 feels sloppy as though it's going to damage the key or the grub screw, if the grub gets damaged it's trouble! Will get a 1/16 which is 1.588mm, 2mm is to big
Thanks
Dave
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Old 21st Jan 2020, 1:17 am   #4
jonvk2fsw
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Default Re: JRC JST-135 Vfo knob removal

HI the hex key you need 1.45 mm or 57.5 thou . A very odd size but I just checked the one on my nrd525 knob .all the best JON VK2FSW PS a 1.5 mm may fit but seems very tight
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Old 21st Jan 2020, 6:56 am   #5
Radio1950
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Default Re: JRC JST-135 Vfo knob removal

Hi there,

I just checked, and my JRC NRD515, an earlier receiver, has knobs with 2.00mm AF "allen type" grubscrews.

Imperial 5/64 inch also "feels" correct size, but I am sure that my knobs would be 2.00mm ex factory.

This would correlate with your finding that 1.5mm AF is 'loose".

May not be applicable to your knobs, so double check.

Very good luck to you.
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Old 21st Jan 2020, 6:42 pm   #6
Final anode
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Default Re: JRC JST-135 Vfo knob removal

Thanks everyone, I got it off! A 1/16" 1.588mm fitted perfectly but it still wouldn't budge! So I used a piece of 10 gauge wire put it into the hole and the hex key head, I then heated the wire with a soldering iron being careful not to catch the plastic, heat conducting down to the grub did the trick, JRC must have used various size grub screws during production, got the pcb off now to change the faulty tact switches, BTW its a fantastic rig, superb receiver, has the 240hz filter which is too narrow looking for a 500hz, read some were you can use Kenwood or Icom, can anyone confirm?
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Old 21st Jan 2020, 9:15 pm   #7
g4aaw pete
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Default Re: JRC JST-135 Vfo knob removal

Quote:
Originally Posted by Final anode View Post
read some were you can use Kenwood or Icom, can anyone confirm?
Think the orientation of the in / out pins may be differnt.
Shown is the underside of a Kenwood filter.
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Old 21st Jan 2020, 10:49 pm   #8
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Default Re: JRC JST-135 Vfo knob removal

Yes Pete thanks, the JRC is in line & 2 threaded studs, it's the Icom I think fits but the grounds are soldered the FL52A somewhere I've seen it mentioned online, not sure on the impedance though, probably better of waiting for a JRC one to pop up on ebay.
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