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Old 4th May 2019, 9:52 pm   #1
Nanozeugma
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Default Murphy A48 tuning drum.

Just acquired an A48.
The tuning drive cord was snapped - didn't take long to sense why...
The vertical drum was jammed solid.
On it's own it runs true and free on it's pivots.
However when the clear cover is in place it jams it.
It's obviously bowed inward due to age / heat / chemical shrinkage.
I would imagine it had been like this for some time as it had ground away a fair amount of the printing.
You couldn't pack it out as it would then foul on the cabinet.

Any thoughts?
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Old 4th May 2019, 10:08 pm   #2
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Default Re: Murphy A48 tuning drum.

Reduce the drum diameter? Move the pivot points backwards?
I assume the frame is bakelite, so it won't straighten without breaking, could you reduce the thickness?
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Old 5th May 2019, 11:05 am   #3
Karen O
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Default Re: Murphy A48 tuning drum.

I can see some spacers/shock mounts, or something. Might these have collapsed, and caused the drum to move forward thus hitting the clear cover?
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Old 5th May 2019, 11:44 am   #4
Lloyd 1985
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Default Re: Murphy A48 tuning drum.

If it’s just the clear cover that’s deformed over time, could you not just replace it? I replaced the clear plastic tuning scale cover on an old Ekco once, it was a curved shape originally, and had suffered damage from something falling on the set in its past, I replaced it with some thin clear plastic I got from work, it was either 1mm or 0.5mm, can’t remember off hand now, but it was easy to bend it to the curvature of the original, and the set looks a whole lot better with a nice clear unbroken scale!

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Old 5th May 2019, 2:55 pm   #5
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Default Re: Murphy A48 tuning drum.

Last time I looked at one of these I think the drum suspension frame is either part of or attached to the tuning capacitor. On mine as is often the case the rubber mounting grommets on the tuning capacitor mounting screws had disintegrated causing the entire assembly to list to one side so the drum was fouling. Replacement of the grommets was the answer but it was a fiddling job as there isn't a lot of space to work. Cheers, Jerry
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Old 5th May 2019, 3:18 pm   #6
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Default Re: Murphy A48 tuning drum.

Hi people and thank for your input and suggestions.

The problem is definitely the clear plastic drum cover which bears the station names - or did! It is distorted.

The tuning capacitor shock mounts are well on the way to extinction but have not collapsed so the tuning capacitor / mount / drum do not lean.

It would have been nice to find an image of an undamaged cover on t'web but so far no luck - I've seen one remarkably similar to mine though - looks like a common problem.
This would have helped replicating the station names, many now worn away.
You can clearly see the abrasion marks where the drum has ground against the back of the cover.

I've appended a few images of the various bits in case anyone is interested.
Looks like I shall be playing silly ******* with plastic sheet and Letraset (if I can find the correct Font.)
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Old 5th May 2019, 3:57 pm   #7
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Default Re: Murphy A48 tuning drum.

Guess I'm lucky my A48 is fine, but I also have a A50 with exactly the same drum set up and this has done the same thing as yours with the station names rubbed away. Mechanically everything is fine I suspect it's shrinkage over time. I elongated the holes on this station name perspex, it gives it a bit more size to re-adjust the curve and clear the rotating drum.
I'll be interested to see how you replicate the text, sounds like it's going to be challenge.
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Old 5th May 2019, 8:52 pm   #8
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Default Re: Murphy A48 tuning drum.

Ah, didn’t notice from the first post that the names are actually printed on the clear bit. I wonder if water slide transfers could be used?

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Old 6th May 2019, 12:23 am   #9
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Default Re: Murphy A48 tuning drum.

Quote:
Originally Posted by MurphyNut View Post
Guess I'm lucky my A48 is fine, but I also have a A50 with exactly the same drum set up and this has done the same thing as yours with the station names rubbed away. Mechanically everything is fine I suspect it's shrinkage over time. I elongated the holes on this station name perspex, it gives it a bit more size to re-adjust the curve and clear the rotating drum.
I'll be interested to see how you replicate the text, sounds like it's going to be challenge.
It will, indeed, be a challenge
I've yet to source a suitable clear flexible plastic replacement (which is about 0.5mm thickness.)

As you evidently possess an undamaged example, I don't suppose I could persuade you to photograph it (for a complete station name list) could I?
Kind regards in any event Clive...
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Old 6th May 2019, 12:27 am   #10
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Default Re: Murphy A48 tuning drum.

Quote:
Originally Posted by Lloyd 1985 View Post
Ah, didn’t notice from the first post that the names are actually printed on the clear bit. I wonder if water slide transfers could be used?
A nice idea Lloyd, but I apprehend some difficulty in sourcing ready made transfers for things like Hilversum and Kalundborg
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Old 6th May 2019, 9:02 pm   #11
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Default Re: Murphy A48 tuning drum.

Worth a phone call to Mike Lewis. I have sent you a PM with his phone number and have spoken to him previously to make sure that he doesn't mind me passing it on. He has an extraordinary stock of bits and pieces so might possibly have a replacement dial drum or even a complete scrap chassis. I know he has a number of radios with terminal woodworm to dispose of so you never know. Cheers, Jerry
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Old 6th May 2019, 9:52 pm   #12
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Default Re: Murphy A48 tuning drum.

Thanks Jerry, I will give him a ring tomorrow, much obliged.
Kind regards, Colin.
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Old 8th May 2019, 11:52 am   #13
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Default Re: Murphy A48 tuning drum.

I wonder if it would be possible to apply some heat to original and attempt to reshape it, possibly using some doweling or metal tubing as a buck?

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Old 8th May 2019, 5:00 pm   #14
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Default Re: Murphy A48 tuning drum.

Hi Peter, thanks for your input.
If all the text was still present, i might be tempted to try.
As a good deal of the text has been ground away, it's looking like having to try replicating from scratch with modern materials - unless some kind soul can source an original in good condition from a scrapper...
Kind Regards,
Colin.
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Old 8th May 2019, 6:22 pm   #15
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Default Re: Murphy A48 tuning drum.

Quote:
Originally Posted by Nanozeugma View Post
I've yet to source a suitable clear flexible plastic replacement (which is about 0.5mm thickness.)
How about a large soft drinks plastic bottle? Most are completely clear and easy to work, I have made several dial cover replacements from them.
Water slide print inside?

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Old 9th May 2019, 8:40 am   #16
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Default Re: Murphy A48 tuning drum.

Quote:
How about a large soft drinks plastic bottle?
Hmmmm... I'll have a look...
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Old 11th May 2019, 8:49 pm   #17
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Smile Re: Murphy A48 tuning drum.

Try a R Whites Lemonade bottle (lemonade removed first though!!) This is nice and transparent and of a decent size and although the thickness will be a little less it should be more than adequate for a tuning window.
Christopher Capener
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Old 11th May 2019, 9:20 pm   #18
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Default Re: Murphy A48 tuning drum.

Nah, Morrison's Ginger Beer 2 ltr bottle, more bite!
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Old 12th May 2019, 9:54 am   #19
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Default Re: Murphy A48 tuning drum.

I concur - always liked Ginger Beer...
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