Discussion:
Need idler solution for RCA SHF-7 circa 1958
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John-Del
2017-11-26 03:20:36 UTC
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One of my customers dropped off this hifi to be done before Christmas. It's got the usual bag of issues but the biggest one is the idler pulley. The rubber tire is now some sort of plastic and cracked; no chance of turning it down to expose soft rubber.

Does anyone know of a source for the idler tire or an off the shelf O-ring that might fit or one that can be modified to fit?

John
Wolcott, CT
Foxs Mercantile
2017-11-26 05:14:45 UTC
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Post by John-Del
One of my customers dropped off this hifi to be done before Christmas. It's got the usual bag of issues but the biggest one is the idler pulley. The rubber tire is now some sort of plastic and cracked; no chance of turning it down to expose soft rubber.
Does anyone know of a source for the idler tire or an off the shelf O-ring that might fit or one that can be modified to fit?
John
Wolcott, CT
<https://www.mcmaster.com/#o-rings/=1af20e1>
--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com
John-Del
2017-11-27 21:22:04 UTC
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Post by John-Del
One of my customers dropped off this hifi to be done before Christmas. It's got the usual bag of issues but the biggest one is the idler pulley. The rubber tire is now some sort of plastic and cracked; no chance of turning it down to expose soft rubber.
Does anyone know of a source for the idler tire or an off the shelf O-ring that might fit or one that can be modified to fit?
John
Wolcott, CT
I ended up taking an old stock capstan belt from a camcorder and cutting it down to size to stretch over the original hardened tire that I chose to leave in place. The fresh new "tread" added some OD to the idler tire but it still clears so no binding. So far, so good. Smooth and quiet. Further info: this is an RCA changer RP-205. Pretty common unit covering many years. Looks like a VM copy.

I'm actually surprised how good the sound is on this old table model mono HiFi. Also surprised to find this has push pull 6V6 outputs and three speakers. Probably good for an honest 10W I'd guess.

John
Wolcott, CT
Peter Wieck
2017-11-27 21:54:15 UTC
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Jeff nailed it in one as a source for O-rings - but my habit is to turn down the Idler )---II---( like so. Then pop on a nice soft O-ring O)---II---(O like so. A dab of super-glue (make sure it spans the full 360) and you will be home-free. This can be done by chucking the idler in a drill or a Dremel, and just touching lightly it with a round file, at a moderate speed.

And, most old-fashioned hardware stores (we have one nearby) has a box of O-Rings of all sorts of sizes. And often faucet-repair kits will yield useful ones as well.

Peter Wieck
Melrose Park, PA
John-Del
2017-11-28 00:21:29 UTC
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Post by Peter Wieck
Jeff nailed it in one as a source for O-rings - but my habit is to turn down the Idler )---II---( like so. Then pop on a nice soft O-ring O)---II---(O like so. A dab of super-glue (make sure it spans the full 360) and you will be home-free. This can be done by chucking the idler in a drill or a Dremel, and just touching lightly it with a round file, at a moderate speed.
And, most old-fashioned hardware stores (we have one nearby) has a box of O-Rings of all sorts of sizes. And often faucet-repair kits will yield useful ones as well.
Peter Wieck
Melrose Park, PA
I don't have a lot of time to mess with this as it's not my main area of service (I do these things for prior customers) most particularly at this time of year. The flat belt retread fixed it and I'm inclined to ship it that way. If something goes wrong I'll consider an O-ring solution.

Good tip about the hardware store. There's one - one town away that I frequent just because it has been there over a hundred years and owned by the same family. Good chance they'd have a selection that might yield a suitable candidate.

If I could identify the correct size (I would actually prefer a square seal) and if I did these routinely I'd order a metric crap load of them from McMaster. I was hoping someone said "I do these all the time, use xx-xxx", just pops right in."

John
Wolcott, CT
John-Del
2017-11-30 19:29:07 UTC
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Post by John-Del
Post by Peter Wieck
Jeff nailed it in one as a source for O-rings - but my habit is to turn down the Idler )---II---( like so. Then pop on a nice soft O-ring O)---II---(O like so. A dab of super-glue (make sure it spans the full 360) and you will be home-free. This can be done by chucking the idler in a drill or a Dremel, and just touching lightly it with a round file, at a moderate speed.
And, most old-fashioned hardware stores (we have one nearby) has a box of O-Rings of all sorts of sizes. And often faucet-repair kits will yield useful ones as well.
Peter Wieck
Melrose Park, PA
I don't have a lot of time to mess with this as it's not my main area of service (I do these things for prior customers) most particularly at this time of year. The flat belt retread fixed it and I'm inclined to ship it that way. If something goes wrong I'll consider an O-ring solution.
Good tip about the hardware store. There's one - one town away that I frequent just because it has been there over a hundred years and owned by the same family. Good chance they'd have a selection that might yield a suitable candidate.
If I could identify the correct size (I would actually prefer a square seal) and if I did these routinely I'd order a metric crap load of them from McMaster. I was hoping someone said "I do these all the time, use xx-xxx", just pops right in."
John
Wolcott, CT
Follow up: The retreaded idler works perfectly on this RP-205 changer. I took an old wide flat capstan belt and cut it about a quarter inch smaller than the circumference of the idler, glued the *carefully* cut ends together, and stretched it over the old idler. I ran a bead of cyano around the circumference to keep the new belt from "inchworming" along the outside of the tire. I chucked it into my drill and gave it a light buzz against an abrasive stone to smoothen the glue seam and minimize any high spots.

I also chucked up and spun the turrets to give the rubber tires (no cracks, fairly soft) some bite. Cleaned and degreased all the surface contact parts and reassembled everything with a bit of spindle oil.

The motor (Alliance) was running slow even with some fresh oil in it so I pulled it apart and soaked the bearings in carb cleaner, and let them dry. I refilled the bearing wick cups with spindle oil and reassembled. Runs immediately at speed and doesn't lose speed with the changer cycling. It also runs just slightly warm after a couple of records, but not hot.

I should have mentioned that the first issue I encountered was what was probably a few ounces worth of grip solution slathered on every rubber surface and the inside of the platter. Looked like a murder scene. It dissolved and cleaned up with acetone.

A friend had a new needle/cartridge (stupid powerpoint deal) so I bought that from him to replace the skating and dull LP needle. A tweak for the landing adjustment finished it.

They picked it up a few days ago and were thrilled with the way it played. Strangely, the amp looks all original and played nicely with no noises or hums anywhere. I suggested that it should be recapped in the near future. They may bring it back after Christmas.

John
Wolcott, CT
g***@gmail.com
2017-12-12 00:57:00 UTC
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Post by John-Del
One of my customers dropped off this hifi to be done before Christmas. It's got the usual bag of issues but the biggest one is the idler pulley. The rubber tire is now some sort of plastic and cracked; no chance of turning it down to expose soft rubber.
Does anyone know of a source for the idler tire or an off the shelf O-ring that might fit or one that can be modified to fit?
John
Wolcott, CT
You may look at casting a new part. I am working on an AP1 1960 RCA automobile 45 rpm record player and will have to cast the bellows that support the base and the rubber idler roll ??
John-Del
2017-12-12 16:09:43 UTC
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Post by g***@gmail.com
Post by John-Del
One of my customers dropped off this hifi to be done before Christmas. It's got the usual bag of issues but the biggest one is the idler pulley. The rubber tire is now some sort of plastic and cracked; no chance of turning it down to expose soft rubber.
Does anyone know of a source for the idler tire or an off the shelf O-ring that might fit or one that can be modified to fit?
John
Wolcott, CT
You may look at casting a new part. I am working on an AP1 1960 RCA automobile 45 rpm record player and will have to cast the bellows that support the base and the rubber idler roll ??
I don't think anything that extreme needs to be done with this particular idler tire. As Jeff and Peter suggested above, just milling a groove into the original hardened tire and dropping an O-ring into the groove is suitable repair for this particular idler tire. The wheel itself will last forever. If a square cross section O-ring seal is available in the same size, then removing the old tire from the wheel entirely and installing the square seal would be even better IMO.

In any case, time was of the essence and I repaired it by retreading it with a sectioned flat belt as described above and sent it home where it's playing Christmas Carols every day. They called me several days ago and are thrilled with how it's playing. Their father in particular couldn't believe it would ever play again (he's in his 90s and bought it new). If it throws the belt in the future I'll go with a better solution.

Do you have a pic posted anywhere of the bellows for that AP-1?

John
Wolcott, CT

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