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Hello guys.  I have a L&R watch cleaning machine that works but the speed control rheostat knob doesn't work well.  Does anyone know of a replacement part for this?  or a good substitute?  I found one by Allied a RHS25RE.  It's a 1 amp 25 Ohm and good to 550 volts.  I know the Master machines are 115 volt at 75 cycles.  Would this work?

I would like to get my machine back up and running again.

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5 hours ago, SonnyBurnett said:

 the speed control rheostat knob doesn't work well.  Does anyone know of a replacement part for this?

Normally, especially on conservative restorations, these are cleaned . You can drop it in e.g. Isopropil alcohol, then blow compressed air into it 

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11 hours ago, SonnyBurnett said:

Does anyone know of a replacement part for this? 

Just like in watch repair a general description of I have a watch and it needs a part just doesn't cut it. We would really need to see what the original part looks like and its characteristics like numbers it has on it then we can pick a replacement because conceivably it's not the only one in the universe they ever used and I seriously doubt most people even have a clue of what that uses unless they ever replace there's providing they even have one.

 

11 hours ago, SonnyBurnett said:

RHS25RE

Then for all of us that don't grasp what that is by just the part number I have a picture and it looks expensive. Now that I can see what it is I think the cleaning device up above is good. 

 

https://www.digikey.com/en/products/detail/ohmite/RHS25RE/824061

 

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12 hours ago, jdm said:

Normally, especially on conservative restorations, these are cleaned . You can drop it in e.g. Isopropil alcohol, then blow compressed air into it 

Well I'd have to un-solder  to take it out, so if I'm going to do that, I'm going to replace it, especially since the brass band around the stem has broken loose.

 

6 hours ago, JohnR725 said:

Just like in watch repair a general description of I have a watch and it needs a part just doesn't cut it. We would really need to see what the original part looks like and its characteristics like numbers it has on it then we can pick a replacement because conceivably it's not the only one in the universe they ever used and I seriously doubt most people even have a clue of what that uses unless they ever replace there's providing they even have one.

 

Well, it's an L&R precision cleaning machine Master model.  The speed control rheostat is the knob in the very front that controls the speed of the motor.  I have it apart at work, I'll take some pics of it but it doesn't have any numbers on it that I remember seeing.

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If it is a wire wound rheostat, you don't have to replace it. Just spray it with contact cleaner and work the knob a few times to grind away the oxide layer on the wire coils and it will be fine.

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15 hours ago, HectorLooi said:

If it is a wire wound rheostat, you don't have to replace it. Just spray it with contact cleaner and work the knob a few times to grind away the oxide layer on the wire coils and it will be fine.

Correct. I was one of these "take everything apart" guys, now with age better wisdom is growing.

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Back in the old days when you did not have a clicker to change channels on your TV, there was a rotating mechanical channel selector to perform this task (and back then, the reason people bore children was so that they could order them to get off the couch and change the channel!!)  The contacts would oxidize and result in intermittent continuity.  They sold "Tuner Cleaner" spray that you sprayed on the contacts as you spun the channel selector.  I cleaned a lot of tuners during my years as a TV tech.

Yes, I agree that a wire-wound rheostat should work perfectly fine after spraying with contact cleaner spray.  There is, of course, the possibility that the wiper is mechanically compromised...in which case cleaner will not solve the problem.

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On 11/20/2021 at 7:19 PM, HectorLooi said:

If it is a wire wound rheostat, you don't have to replace it. Just spray it with contact cleaner and work the knob a few times to grind away the oxide layer on the wire coils and it will be fine.

Here is the Rheostat.  I can get the machine at work if more pics are needed. I'm an electrician for a hospital so I have it at work for the repair.  There seems to be a brass ribbon soldered to the wiper that is wrapped around the shaft.  You can't see it well in these pics.  I was concerned about creating a short if it touches the wire.

I haven't tried cleaning it yet and I won't mess with it until I solder on a new cord.  All the old rubber insulation has vulcanized and falls off if you breathe near it.

 

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Edited by SonnyBurnett
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8 hours ago, Plato said:

No way I'd reuse that part, it's already been mucked about with, replace it with a new pot. I bet the knob is a standard size used today.

https://uk.rs-online.com/web/c/passive-components/variable-resistors/potentiometers/?searchTerm=potentiometer

that was my first thought.  "This has been messed with" but it's old and this is my first machine, I thought it could have just been a bit crude.                                                                                                                                                      I kind of want to replace it too.  Problem is like with your link you sent me, I don't know what replacement part I actually need.  I talked to Dave at Dave's Watch Parts and said he used to buy them at www.surplussales.com, but I still don't know exactly what to get.  115 volt at 75 cycles and I think it's 60 Ohm.

Edited by SonnyBurnett
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23 minutes ago, SonnyBurnett said:

that was my first thought.  "This has been messed with" but it's old and this is my first machine, I thought it could have just been a bit crude.                                                                                                                                                      I kind of want to replace it too.  Problem is like with your link you sent me, I don't know what replacement part I actually need.  I talked to Dave at Dave's Watch Parts and said he used to buy them at www.surplussales.com, but I still don't know exactly what to get.  115 volt at 75 cycles and I think it's 60 Ohm.

I don't suppose you can find a circuit diagram? I sent the wrong link too, this is the correct link:

https://uk.rs-online.com/web/c/passive-components/variable-resistors/rheostats/

There must be something equivalent to what you need. But, like others have said, it might look/work a lot better when cleaned. 

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9 hours ago, SonnyBurnett said:

Dave contacted me and said this one might work.  Anyone got any thoughts?  Its on the very bottom of the page.

(RWA) A-29418-5

  https://www.surplussales.com//Potentiometers/Rheostats/PotsRheost-3.html.

Do you mean the (RWA) RP151SD750KK? I can't find (RWA) A-29418-5.

75ohm would be near enough to 60ohm for a rheostat provided it can cope with the current/power.

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14 hours ago, Plato said:

Do you mean the (RWA) RP151SD750KK? I can't find (RWA) A-29418-5.

75ohm would be near enough to 60ohm for a rheostat provided it can cope with the current/power.

At the very bottom of the page in the link on the right side.  The last one.  On my screen it shows up as (RWA) A-29418-5

Rheostat, 800 ohm, 50 watt, 0.25 amp. Type R-50. 2-1/4" diameter body, 1-3/8" behind panel depth. 1/4" diameter x 1/2" long round shaft. Made by Memcor. NSN: 5905-01-013-4370.

Dave said this one is close enough it should work.  One thing I noticed is the wattage.  it's 50 watt and the machines are rated at 60.  Also the amperage, seems low.  Can't remember what the machine runs at.

Edited by SonnyBurnett
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