B&O RX-2 Belt Length

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msp1
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B&O RX-2 Belt Length

Post by msp1 » 13 Jun 2018 06:56

I'm new to the forum, and have a B&O RX-2 that "drags" each time the tonearm drops. I'm not finding much in the way of reliable sources online for a replacement belt. One of the websites (turntablebasics.com) calls for a 29.5" belt (out of stock), which differs from most other models. An EBay seller lists a 27.3" belt to fit all these models --1800, 2000, 2200, 3000, 5000, RX-2, which contradicts the other site. Before I pull mine apart, possibly risking the old (original )belt integrity without a replacement in-hand, does anyone know where I can find the proper belt length? It's not spec'd in the service manual, just "belt" and a part #. Also, any ideas where to find a good belt?

Thanks
Mike

Coffee Phil
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Re: B&O RX-2 Belt Length

Post by Coffee Phil » 13 Jun 2018 17:42

Hi Mike,

Welcome to the forum.

Sadly, B&O no longer supports their turntables. We have to look elsewhere.

Here is a link to the manual: https://www.vinylengine.com/library/ban ... -rx2.shtml

First off remove the top platter and lightly place your finger on the sub platter with the motor running to determine if the belt is slipping or the motor is slowing. If the belt is slipping remove it and measure the length. Assume it has stretched and reduce the number by ~ 5%. Measure the thickness and width if it is a flat belt or the diameter if it is round. With those numbers call Gary at Voice of Music.

http://www.thevoiceofmusic.com/

He may be able to Help you. He may even be able to work from the model number of your machine.

If the old belt is not slipping, but rather the motor is slowing, some trouble shooting will be required.

Phil


msp1 wrote:I'm new to the forum, and have a B&O RX-2 that "drags" each time the tonearm drops. I'm not finding much in the way of reliable sources online for a replacement belt. One of the websites (turntablebasics.com) calls for a 29.5" belt (out of stock), which differs from most other models. An EBay seller lists a 27.3" belt to fit all these models --1800, 2000, 2200, 3000, 5000, RX-2, which contradicts the other site. Before I pull mine apart, possibly risking the old (original )belt integrity without a replacement in-hand, does anyone know where I can find the proper belt length? It's not spec'd in the service manual, just "belt" and a part #. Also, any ideas where to find a good belt?

Thanks
Mike

msp1
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Re: B&O RX-2 Belt Length

Post by msp1 » 14 Jun 2018 07:14

Thanks Phil for the quick reply. I did some experimenting, and it's not clear that the belt is slipping when I apply a little pressure to the sub-platter. The belt does seem fairly loose, but I have no experience with how tight a new belt should be. I can make it slip a bit by pulling on the belt.

I can say that, under load of top platter, an album, and the tonearm assy., continuous music sounds okay. If I cue the tonearm up and back down, the music slows quite noticeably for a second before catching back up to normal speed. It does make me wonder how accurate/constant the speed is while playing. I was thinking a replacement belt could be a cheap test and possible fix if I could find the proper belt, but not if it's really a motor/other problem.

Does that warrant further debug?

BTW, the old belt is 29.5" x 3/16" flat.

Thanks,
Mike

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Re: B&O RX-2 Belt Length

Post by Coffee Phil » 14 Jun 2018 08:26

Hi Mike,

I’m thinking a new belt may Help. You don’t want the belt tight enough to put a large bearing load on the platter bearing or motor bearing but it should not be loose. If Gary does not have a recommended belt for your our machine ask for one 28” in length with the same width. If he also has one with the correct thickness that would be good. Belts do effect platter speed, however your machine has a servo controlled DC motor which is adjustable so you don’t have to fret as much over an exact belt as if you had a mains driven synchronous motor.

With the new belt you will have to adjust speed. It should be no big deal. I’m sure the procedure is in the service manual.

Do keep us posted on the progress.

Phil
msp1 wrote:Thanks Phil for the quick reply. I did some experimenting, and it's not clear that the belt is slipping when I apply a little pressure to the sub-platter. The belt does seem fairly loose, but I have no experience with how tight a new belt should be. I can make it slip a bit by pulling on the belt.

I can say that, under load of top platter, an album, and the tonearm assy., continuous music sounds okay. If I cue the tonearm up and back down, the music slows quite noticeably for a second before catching back up to normal speed. It does make me wonder how accurate/constant the speed is while playing. I was thinking a replacement belt could be a cheap test and possible fix if I could find the proper belt, but not if it's really a motor/other problem.

Does that warrant further debug?

BTW, the old belt is 29.5" x 3/16" flat.

Thanks,
Mike

msp1
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Re: B&O RX-2 Belt Length

Post by msp1 » 15 Jun 2018 07:40

Hi Phil,

I hadn't even thought about re-calibrating the speed. I don't know of anyone who might have a turntable strobe. I hope a printed strobe mat and 60Hz incandescent light will be close enough, or an app like RPM Calculator (or both). I do have an old Sears timing light, but no spark plug wires on a turntable to sync to...

I'll order the belt, and take it from there. Thanks!

-- Mike

Coffee Phil
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Re: B&O RX-2 Belt Length

Post by Coffee Phil » 15 Jun 2018 19:26

Hi Mike,

You can print one of these strobe discs from this site. It will be very accurate. Incandescent lamps do work but the contrast will be poor as they do not respond to the voltage as rapidly as neon or non electronic ballasted fluorescent lamps do.
https://www.vinylengine.com/strobe-discs.

If you have an old fluorescent lamp with what is called a magnetic ballast it will be good.

Good strobes can be made with LEDs. The circuit as well as a demo of one which I did is in this thread: https://www.vinylengine.com/turntable_f ... ht#p896583

Phil

msp1 wrote:Hi Phil,

I hadn't even thought about re-calibrating the speed. I don't know of anyone who might have a turntable strobe. I hope a printed strobe mat and 60Hz incandescent light will be close enough, or an app like RPM Calculator (or both). I do have an old Sears timing light, but no spark plug wires on a turntable to sync to...

I'll order the belt, and take it from there. Thanks!

-- Mike

msp1
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Re: B&O RX-2 Belt Length

Post by msp1 » 01 Jul 2018 07:23

Update:
I sent the old belt to Gary at V-M Audio Enthusiasts for an accurate measurement. He measured 28.85" IC x .95 = 27.4", which is right on for the 27.3" belt. I installed it, and did my best to re-calibrate the speed. I tried the Strobily app on my phone with a printed paper strobe disc. I couldn't get a consistent read though. I also used the RPM Calculator app as well, which I understand is not as accurate as a strobe. I also realized the platter has strobe patterns, which I believe are calibrated for 50Hz (being European made), but I think I'd need to find/build a real strobe light. I'd always wondered why nicer turntables used to have the built-in light, and when one would use it. This would have been the time.

In any case, I played a couple of old albums which sounded good. I do still get some lag when the tonearm drops, though it seems somewhat better. I expect there's something more with the motor or other internals starting to go. I'm not sure this turntable is worth that much more in parts, but I can live with the behavior for now, unless it worsens.

Thanks for all the info.!

-- Mike

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Re: B&O RX-2 Belt Length

Post by kimchi » 02 Jul 2018 19:03

Don't be discouraged! You have a great-sounding turntable and you're nearly finished so don;t give up so easily.

msp1
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Re: B&O RX-2 Belt Length

Post by msp1 » 03 Jul 2018 03:49

What would be the next in debugging the lag?

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