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Old 17th Oct 2019, 9:48 am   #1
Join Date: Oct 2019
Location: Sheffield, South Yorkshire, UK.
Posts: 2
Default Yaesu FRG-7 main frequency tuning dial broken/sticking

Hello all,

I've just moved house and I'm trying to set up a little shack in order to eventually take my Foundation license.

I have an old FRG-7 (well, a newer one, with the fine tuning dial) that my dad got me when I was a boy.

I've set it up, cleaned it out, and stuck 40' of wire into the man antenna connector (PL259). Works ok, I picked up some good CW on 20m.

But when I tried to WebSDR it to check calibration, I was quite a ways out.

Turns out my main tuning dial only rotates through about 700kHz (instead of the full 1000kHz). It will rotate to its maximum clockwise turn and stop, but about seven-tenths of the way back, it jumps, like a cog or thread is skipping. I have a video but I don't think the forum accepts those sorts of files.

I had it open and I can't readily see the problem, because the VFO (?) assembly is behind all those plates.

Just after a bit of advice - has anyone seen the issue before, or have any idea which part of the mechanism is responsible for the max/min turn of the tuning shaft?

Thanks in advance!
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Old 20th Oct 2019, 4:28 pm   #2
Join Date: Nov 2011
Location: Chippenham, Wiltshire, UK.
Posts: 213
Default Re: Yaesu FRG-7 main frequency tuning dial broken/sticking

There's a nut on the top of the main 0-1000 scale drum (under the S-meter). Make sure that it is tight enough to make sure the drum does not slip.

If the drum is securely fixed and not slipping, then you could remove the nut and then the drum to look underneath. Not sure if that will reveal the drive mechanism but it is sensible to check the mechanics before the electronics.

- Peter (G3PIJ)
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Old 20th Oct 2019, 6:23 pm   #3
Join Date: Oct 2019
Location: Runcorn, Cheshire, UK.
Posts: 5
Default Re: Yaesu FRG-7 main frequency tuning dial broken/sticking

You can turn the dial indicator disc by hand...tune to a known freq and turn the disc or dial...aim from a from mid way ie 5.500kcs as the dial get less accurate as you tune...but at least it will be accurate mid way...easy then to estimate the freq as you move away from the ctr figure.

Hope that makes sense.

Nick in the UK 2E0LPL.

It will be stiff.

I have one...had to do it with mine.

How long since it was last used.

Got mine around 1970 still work well...nice audio...tuning
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Old 25th Oct 2019, 1:41 pm   #4
John KC0G
Join Date: Mar 2009
Location: Minneapolis, Minnesota, USA.
Posts: 199
Default Re: Yaesu FRG-7 main frequency tuning dial broken/sticking

Steelstar, welcome.

I am sorry not to have replied earlier. I have been on the road.

IIRC, the FRG-7 tuning knob turns ten revolutions to cover the 1MHz band. Mounted on the tuning shaft is a set of 10 or so washers with tabs on prevent overtravel at each end of the tuning scale. These slide over each other, until they can slide no further. These washers are greased at the factory. The grease can dry out, and then washers stick together and limit the number of turns of the tuning knob. I think that the sticking washers can be anywhere in the stack

This happened to a friend's radio. Together we removed the washers from the tuning shaft, and cleaned off all of the dry grease. This was several years ago. We had a tough time getting access to the required area. It should not have been as difficult as it was. We could have overlooked something.

I would start by looking to see if you can see the bank of rotating washers, and going from there.

HTH, and please ask if you have more questions.

73 John
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Old 29th Oct 2019, 11:45 pm   #5
Join Date: Oct 2019
Location: Sheffield, South Yorkshire, UK.
Posts: 2
Default Re: Yaesu FRG-7 main frequency tuning dial broken/sticking


Thanks for your reply. Sorry I havenít responded, I didnít get a notification.

Yes, this was exactly the problem! Looks like one of the rings about halfway down the stack was either sticking or was slightly out of position, so it just kept sticking.

Itís in a really awkward position to service, and so I couldnít see what it was at first. I thought about taking the entire VFO assembly out but didnít want to deal with the (quite tight) desoldering, so I bought a broken Frog from eBay, stripped that down, and worked out fairly quickly what was going on. Good job too, the tuning spindle has nine ball bearings in it, and readjusting these rings guarantees theyíll all fall out.

In the end, and because it was a fiddly job, I replaced the entire set of rings with those from the donor, which were in great shape.

Iíve tried to highlight the problematic component in the attached picture, in case anyone else comes up against this issue. FYI, to reassemble the mechanism without un-mounting the VFO, you need the radio panel-down on a desk so the spindle is vertical and the ball bearings are held by gravity. Not easy.

Now I just need to get it on a known-good antenna so I can see if itís aligned correctly or if I have another problem (difficult to fully fine-tune even strong signals like Shannon VOLMET). I have a 7700 winging its way to me just in case!

Thanks again, and if anyone wants a non-functional late-model FRG-7 with a detachable VFO, give me a shout!
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