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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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14th Feb 2018, 5:10 pm | #1 |
Heptode
Join Date: Apr 2015
Location: Manchester, UK.
Posts: 711
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AR-88LF. Tuning box.
Hi all , My 88 has backlash in the tuning box I read somewhere that someone had posted up a thread regarding this but I can't find it any help with this would be appreciated thanks Chris .
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14th Feb 2018, 6:57 pm | #2 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,901
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Re: AR-88LF. Tuning box.
There shouldn't be any backlash if it's been assembled properly. All the gears mate with doubled ones which are sprung apart. If someone throws it together without pre-loading the springs you get backlash..... also if the bearings are worn or loose.
David
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14th Feb 2018, 6:59 pm | #3 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 14,007
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Re: AR-88LF. Tuning box.
There shouldn't be backlash. The design of the large tuning-gears is that they are each made of two separate gears whose mesh with the other gears is controlled by small coil-springs interposed between them so the two large gears are kept in tension.
What can happen though is that over the intervening decades the original lubricant can go hard - this then essentially glues the two gears together and prevents the anti-backlash springs from doing their thing. The answer is of course to strip out the gearbox, separate the pairs of gears [watch out for flying springs!] and use a suitable solvent to remove all the old congealed grease - then reassemble using a light oil or semi-fluid grease [I use the 'moly-grease' intended for constant velocity joints on front-wheel-drive cars]. It takes time and effort, but you should be rewarded with a velvety-smooth backlash-free tuning drive. |
14th Feb 2018, 7:36 pm | #4 |
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Join Date: Dec 2010
Location: Exeter, Devon and Poole, Dorset UK.
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Re: AR-88LF. Tuning box.
I have a spare recovered AR88 tuning assembly no idea about the condition until I drag it out.
However I agree with the previous comments the old lubricant becomes a sort of yellow glue! Cheers Mike T
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14th Feb 2018, 8:26 pm | #5 |
Heptode
Join Date: Apr 2015
Location: Manchester, UK.
Posts: 711
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Re: AR-88LF. Tuning box.
Thanks for your replies guys the springs that keep the tension on the split gears are loose so I guess that's not helping . I will remove the box on Friday (day off) and let you know .
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14th Feb 2018, 10:36 pm | #6 |
Octode
Join Date: Dec 2010
Location: St Ives, Cambridgeshire, UK.
Posts: 1,180
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Re: AR-88LF. Tuning box.
Chris,
Here's two threads linked below which may be the ones you saw. https://www.vintage-radio.net/forum/...d.php?t=117076 https://www.vintage-radio.net/forum/...ad.php?t=77441 Andrew
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14th Feb 2018, 11:59 pm | #7 |
Heptode
Join Date: Apr 2015
Location: Manchester, UK.
Posts: 711
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Re: AR-88LF. Tuning box.
Excellent Andrew thanks some good details and pics from Gezza and co should help me get to grips with it .
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