So the turntable in question is a pioneer rondo 3000x/y.
Everything seems to work fine except for speed.
My ac power is exactly 50Hz. And I've sanded off the 50 years worth of shmuts off the belt drive spindle...
But still to my ear its running noticeably fast. Basic app test shows 33.9rpm and 46.0rpm (both +/- 0.1rpm)
I cant see any adjustment pots on the motor
I tried to find a service manual but was unsuccessful.
And I've tried to google 'speed adjustment' but still couldn't find anything.
If there really isnt any speed adjustment, is it just a case of replacing dried out lubrication?
Thanks 🙂
Everything seems to work fine except for speed.
My ac power is exactly 50Hz. And I've sanded off the 50 years worth of shmuts off the belt drive spindle...
But still to my ear its running noticeably fast. Basic app test shows 33.9rpm and 46.0rpm (both +/- 0.1rpm)
I cant see any adjustment pots on the motor
I tried to find a service manual but was unsuccessful.
And I've tried to google 'speed adjustment' but still couldn't find anything.
If there really isnt any speed adjustment, is it just a case of replacing dried out lubrication?
Thanks 🙂
I suspect a picture of the motor and surrounding area (any circuit boards) might help. If it is a small DC motor then typically they can have presets located in the motor and accessible via holes in the rear plate. If so be careful not to use a metal screwdriver that can easily short to the case of the motor.
I tried to fix a B&O Beogram turntable many moons ago (30ish years ago). It would run fine at the beginning of the record and then slow down. Lubing the bearings helped, but the problem came back eventually.
Anyway. My point is that I doubt lubrication is your issue. You could always try adding a small drop of sewing machine oil to the bearings and see if that helps. But more lubrication would seem to imply less friction, thus, higher speed.
Tom
Anyway. My point is that I doubt lubrication is your issue. You could always try adding a small drop of sewing machine oil to the bearings and see if that helps. But more lubrication would seem to imply less friction, thus, higher speed.
Tom
I've just spotted this in a write up on HiFi Engine. If this is correct then...
A synchronous motor is locked to the mains frequency although it can be slowed by using an eddy current brake but I've never seen that done on turntable, VCR's yes, but never a turntable. Your quoted speeds may well be within tolerance for a budget deck. The error is 2.7 % @33RPM and 2.2* % @45rpm
When measuring frequency of AC you perhaps need higher resolution than just '50' for example 49.54 or 50.47.
A synchronous motor is locked to the mains frequency although it can be slowed by using an eddy current brake but I've never seen that done on turntable, VCR's yes, but never a turntable. Your quoted speeds may well be within tolerance for a budget deck. The error is 2.7 % @33RPM and 2.2* % @45rpm
When measuring frequency of AC you perhaps need higher resolution than just '50' for example 49.54 or 50.47.
1. It might always have run fast. I recall hearing such TT back in the day. The Rondo 3000 was a pretty low end series.
2. If the motor can be tilted, this might provide some speed adjustment.
3. New belt might be worth trying.
2. If the motor can be tilted, this might provide some speed adjustment.
3. New belt might be worth trying.
That gave me an idea... what about adding a thin flat belt of suitable width around the inner part of the platter that the main drive belt runs on to increase its diameter. I wonder what sort of effect say a 0.8mm belt would have on speed and whether it would alter W/F.
If it's driven by a synchronous motor and the mains frequency is correct the motor should produce the exact required RPM. It then boils down to whether the belt sits correctly on the pulleys.
The mains frequency is usually pretty dead nuts on. If it's out significantly the generators at the power stations get really unhappy. I once built a clock where I used the 50 Hz mains as the time base. It lost/gained only a few seconds over the roughly six months between daylight saving time changes.
Tom
The mains frequency is usually pretty dead nuts on. If it's out significantly the generators at the power stations get really unhappy. I once built a clock where I used the 50 Hz mains as the time base. It lost/gained only a few seconds over the roughly six months between daylight saving time changes.
Tom
In the UK that is true up to a point, the average over 24 hours is usually very accurate but can vary significantly at times of very high demand.
http://www.mainsfrequency.uk/fm-home
From above:
And:
This is the frequency right now here:
And a couple of minutes later:
Sorry, i'll have to send photos tomorrow morning in a few hours. But from what i could see, the motor is wired directly to 240v mains. Its a big chunky boi. Outside ferrite lamination plates are like 2~3 inches wide. I couldn't see anything adjustable on first inspection.
I measured the mains freq with my multimeter. I think it was 49.9x or something. I thought close enough as its less than 50Hz anyway.
Perhaps a new belt is needed after all... Its probably 10+ years old now. Its only recently lost enough tension for the belt to slip off the platter when installing... Though i've just read from google that a loose belt is supposed to cause slow speed... Though its sounded this fast in recent memory, but it might have always. I'm not sure i'm just noticing it more now that i cant unhear it... From my first rpm tests shows a speed +3%... I'm not sure if thats abnormal, but to my ears my grim dark synth songs now sound like their sung by chipmunks lol.
I could sand the spindles a little more but thats probably a bad idea as i cant unsand them...
Would any aussie diyers know where i could source a replacement belt in sydney on short notice? Local pickup might be suitable. Unfortunately jaycar doesn't have the right size 🙁
I measured the mains freq with my multimeter. I think it was 49.9x or something. I thought close enough as its less than 50Hz anyway.
Perhaps a new belt is needed after all... Its probably 10+ years old now. Its only recently lost enough tension for the belt to slip off the platter when installing... Though i've just read from google that a loose belt is supposed to cause slow speed... Though its sounded this fast in recent memory, but it might have always. I'm not sure i'm just noticing it more now that i cant unhear it... From my first rpm tests shows a speed +3%... I'm not sure if thats abnormal, but to my ears my grim dark synth songs now sound like their sung by chipmunks lol.
I could sand the spindles a little more but thats probably a bad idea as i cant unsand them...
Would any aussie diyers know where i could source a replacement belt in sydney on short notice? Local pickup might be suitable. Unfortunately jaycar doesn't have the right size 🙁
Yeah... And for a synchronous motor running at 3600 RPM with a 108:1 reduction gear for that magic 33-1/3 RPM the variation from 49.5 Hz to 50.5 Hz would result in a deviation of 33-0/3 to 33-2/3 RPM. A 1 kHz tone would vary by ±10 Hz. Is that audible? Probably if you switch fast enough between the two but for a slow variation or instantaneous "is this in tune?" test I doubt anyone would notice. Then again, I have not consulted science on this. Maybe humans have better pitch detection than I give us credit for.
For the 49.920 -> 49.982 Hz you show above I highly doubt anyone would notice a difference in pitch. Not thereby said that you could not measure a difference.
Tom
For the 49.920 -> 49.982 Hz you show above I highly doubt anyone would notice a difference in pitch. Not thereby said that you could not measure a difference.
Tom
That's going to be a traditional non adjustable mains synchronous motor a bit like this one. I came across an online comment somewhere suggesting your TT could be similar to a Pioneer PL12D Speed accuracy is quoted as 1% or better. There is a manual for the Pioneer on Vinyl Engine.
I'll be sure to post a video and a link to the original in about 8 hours or so... Maybe i'm over exaggerating or being too sensitive over just 3%, but when listening, all i can imagine is the singer just got kicked in the nuts lol
<3 calvin + hobbes
But, yeah, pretty sure its not a setting issue as there's only 2.
Yeah mines a little bit different. The motor design is quite a bit different too (looked like it had 4x coils or something)
Here's a video that shows the belt drive spindle:
Here's what it sounded like a year ago... And it sounds like its just as fast, if not now is even worse...
I don't know how accurate the RPM test apps are, but I'd imagine they'd be pretty good. Personally I'd probably use a strobe disc. Here's a .pdf that you can print out and use: https://www.quadesl.com/pdf/strobe.pdf Just make sure to use the one appropriate for your mains frequency.
Tom
Tom
You have it set to 45 RPM in the video. At least I counted 45 revolutions in a minute (and 33.3 revolutions in about 46 seconds). I just used a one-minute timer and counted the revolutions manually. If you use the strobe disc I bet you'll find that the 45 marks line up just about perfectly.
Tom
Tom
If you've fitted a new belt be aware that a thicker belt will make the TT run faster.
I don't know what the original belt thickness was but it might be feasible to get a thinner one.
I don't know what the original belt thickness was but it might be feasible to get a thinner one.
