-------- Original message --------
From: Nigel Pugh via Jukebox-list <jukebox-list@lists.netlojix.com>
Date: Fri., Feb. 24, 2023, 11:03 a.m.
To: Steve Wahl via Jukebox-list <jukebox-list@lists.netlojix.com>
Cc: Steve Wahl <steve@pro-ns.net>, Nigel Pugh <pughn@npsyssoft.force9.co.uk>
Subject: [Jukebox-list] Re: Weird Question

I'm in agreement with what Steve says here.

If you like a challenge then I'm sure it can be achieved, but you will end up with an impractical jukebox as I really don't know how many 10 inch 33rpm records are available to give you a good choice of stuff to listen to.

I would convert it to 45 if you want more flexibility, which has been done commercially in the past on that machine.

You will have to make tonearm and cartridge adjustments to make sure you don't grind your LP's into dust, and re engineer the trip mechanism to work with a lighter tracking weight.

If you ever wanted to sell it at a later stage, it would also limit the market of interested buyers.

Regards

Nigel, Uk

>
> On 24 Feb 2023 at 16:25, Steve Wahl via Jukebox-list <jukebox-list@lists.netlojix.com> wrote:
>
>
> Are 10 inch 33 RPM records widely available? (To my knowledge, most
> 33's are 12", and changing a seeburg M100A to 33 was occasionally seen
> because the unmodified M100A could handle both 10" and 12" 78 RPM
> records.)
>
> I've never heard of someone making a 78 based AMI D (or E,F,G) play at
> 33. I think you'd have to roll your own modification to make this
> happen.
>
> I have an AMI F 120, the pictures I recall seeing tell me the details
> would be similar, but I could be wrong about areas where the F differs
> from the D.
>
> The turntable motor turns at a fixed speed derived from the frequency
> of the incoming AC power. The speed of the turntable is set by the
> RPM of the motor and the ratio of the motor spindle size to the
> turntable rim size.
>
> I think in terms of circumference of the two when visualizing this in
> my head, the distance around the motor spindle moving the rim of the
> turntable the same distance in one rotation of the motor. But the
> diameter of each is much easier to measure, and the way the geometry
> works out, the ratio of circumferences is the same as the ratio of
> diameters.
>
> The idler wheel is a single edge contacting both the motor spindle and
> the turntable drive rim, so its size has no bearing on the final
> speed. (If the D has a two-tier idler, with one diameter touching the
> motor and a different diameter touching the TT rim, then it does
> factor in.)
>
> You can change the final speed by either changing the ratio between
> the motor spindle and the turntable rim, or by changing the frequency
> of the power going into the motor. Prior art for this: A player
> designed for 60Hz power (US) will turn slow when run on 50Hz power
> (Europe), and conversion kits compensate for this by increasing the
> diameter of the motor spindle with a coil-spring like colar placed
> around it. And Seeburg multi-speed jukes that could play both 33 1/3
> and 45 RPM did so by powering the motor from electronics that changed
> the frequency.
>
> To go the mechanical route, you'd have to reduce the motor spindle to
> 33/78ths of the original diameter by turning it down with a lathe or
> something. I have no idea how you'd do that accurately, while making
> sure the result is perfectly circular so as not to add wow and/or
> flutter.
>
> Electronically, my math says you'd have to create a power frequency of
> 25.38 Hz (60Hz * 33/78). Again, I have no experience on how you'd
> accomplish that, but there's probably a circuit out there somewhere.
>
> One final thought occurs to me: A YouTube guy, I believe his name was
> Chris Cuff, who is no longer with us, used to convert 45 RPM RCA
> changers to portable, battery powered players. To do this, he would
> substitue a DC motor for the original AC, and I recall the DC motors
> had tunable speed. Substituting a motor of a different (and tunable?)
> speed might be the easiest approach for making a D go 33 RPM.
>
> In short, unless I'm missing something, this is not an easy, well
> traveled road you're looking down!
>
> --> Steve
>
> On Thu, Feb 23, 2023 at 06:56:20AM -0500, Jamie McElroy via Jukebox-list wrote:
> > Hello all,
> > I'm still a bit of a novice but have been fortunate enough to have restored
> > an AMI G-80 and F-80, so relatively the same in most respects but I'm
> > learning.
> >
> > So here is my question. Is it possible to change the speed of the turntable
> > motor on a AMI D-40 Jukebox from 78rm to 33rpms? I don't know if that's
> > possible. Does anyone have any thoughts? I was hoping to restore my D-40
> > and play 10 inch 33 Lps on it. Please let me know if I'm just crazy or this
> > a possibility? Thank you as always.
> >
> > Jamie
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> --
> Steve Wahl steve@pro-ns.net
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