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 Post subject: Re: Amateur horn gramophone, 1930s?
PostPosted: Fri Jan 04, 2019 3:42 pm 
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Victor V
His epigrams are all his own, the man's an epigramophone!
Joined: Mon Oct 24, 2011 1:21 pm
Posts: 2486
Location: The Somerset Levels, UK.
I have found that picking a machine up by holding the turntable rim with both hands, and getting a helper to give the spindle a sharp tap, usually produces the desired result.

Obviously lift the machine no more than half an inch off the work bench, and place something soft such as a folded towel underneath for it to land on.


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 Post subject: Re: Amateur horn gramophone, 1930s?
PostPosted: Mon Jan 07, 2019 7:42 am 
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Victor I
Joined: Thu Apr 27, 2017 5:52 am
Posts: 190
Location: Redruth, Cornwall, U.K.
I have now safely dislodged the turntable. My method was to push a thick piece of cardboard under the turntable, insert two medium-sized screwdrivers (one on each side) between the cardboard and the turntable itself, and then twist the screwdrivers so that the edges of the blades applied pressure upwards. Almost at once the turntable came unstuck, while the cardboard ensured that the wood beneath it was unmarked.

I found that one of the three motor-screws was looking rather battered and had been driven in so far that the washer underneath it was buckled. Evidently the constructor of the gramophone had miscalculated slightly when drilling the hole for the crank, with the result that he had some difficulty in inducing the motor to line up correctly with the hole. I have seen other signs that precision of measurement was not this person's strongest suit!

Oliver Mundy.


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 Post subject: Re: Amateur horn gramophone, 1930s?
PostPosted: Tue Jan 15, 2019 7:42 am 
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Victor I
Joined: Thu Apr 27, 2017 5:52 am
Posts: 190
Location: Redruth, Cornwall, U.K.
The gramophone is now in what is probably its final form, with the Garrard 30 motor and a Meltrope III sound-box installed.

The only problem in fitting the motor was that the socket into which the crank screws apparently stuck out a little farther than the corresponding part of the Garrard 20, with the result that it abutted against the side of the case and pushed the motor off-centre. I had to ream out the hole in the case (fortunately the escutcheon-plate amply concealed the modification) and the difficulty vanished; I suspect that if the various holes in the case had been more precisely located in the first place the change would have been effortless. I can now play the longest twelve-inch sides with comfort. The only slight drawback is that the winding process is more laborious than before, presumably because the gearing is different; I wish I had a crank with a shorter shaft (this, being designed for the larger dimensions of internal-horn cabinets, sticks out too far) and a longer throw. I should say that I re-used the crank from the 20; the new motor had its own crank, but the shaft was even longer.

As for the Meltrope, I have been following the current discussion (http://forum.talkingmachine.info/viewtopic.php?f=11&t=36232&start=20) with interest and had expected that this unusual design would need some tuning. Of course it may yet benefit from this; however, even as it stands it has given me a slight but detectable improvement in the elusive lower frequencies*. At first the higher tones were a little too fierce and 'projected', like those produced by the mica diaphragm of my old H.M.V. No. 4; this however was remedied by simply pushing a wad of tissue-paper into the elbow of the horn, the result being well balanced and not at all muffled or blurred in effect.

*My test record is the pre-war Decca set of Vaughan Williams's Tallis Fantasia by the Boyd Neel String Orchestra. The cello/bass pizzicati near the beginning give a good clue to what one can expect in that register, and the rich string tone would quickly show up an tendency to blast.

Oliver Mundy.


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 Post subject: Re: Amateur horn gramophone, 1930s?
PostPosted: Tue Jan 15, 2019 8:11 am 
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Victor V
His epigrams are all his own, the man's an epigramophone!
Joined: Mon Oct 24, 2011 1:21 pm
Posts: 2486
Location: The Somerset Levels, UK.
A competent model engineer should be able to shorten the winding handle and tap a new thread onto the cut end.

With two springs, the Garrard No.30 motor will take longer to wind than the single spring No.20.


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 Post subject: Re: Amateur horn gramophone, 1930s?
PostPosted: Tue Jan 15, 2019 8:24 am 
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Victor I
Joined: Thu Apr 27, 2017 5:52 am
Posts: 190
Location: Redruth, Cornwall, U.K.
epigramophone wrote:
With two springs, the Garrard No.30 motor will take longer to wind than the single spring No.20.


This of course is what one would expect. In fact, however, the single-spring 20 required about sixty turns for a full wind whereas the 30, despite the extra spring, calls for only fifty; this is why I say that the gear-ratios between crank and barrel must be different. Presumably the makers thought that users of the 30 would not wish to turn the handle a hundred or more times and therefore adopted a higher gearing, which would naturally entail more effort. Or it may be significant that the 30 is an early example with no patents listed on the base-plate whereas the 20 cites two (1928 and 1930); perhaps the ratio was changed during the production run of these motors.

Oliver Mundy.


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