Oracle Delphi MK III speed issues...help

[R-K Rønningstad]

Hi guys.

Wow, that's a very different motor than I have on my Alex MkII. So here's what I would do if I had a motor like that. Firstly, make sure when the rear "can" is put back on the motor, I would endure that it doesn't touch the back plate of the motor.

I would use an "electrical" grease and grease the bushings where the shaft runs through the end plates.. Run the motor without being installed continuously for a few days. Then reinstall it. Use a stethoscope to hunt down the noise if any still. You could also get a rubber band and wrap it around the motor can to reduce standing waves in the metal of the can (used when a mechanic puts car rotors on a brake lathe so that standing waves don't set up inside the rotor and create stress cracks).

This image shows Oracle has isolated the motor from the chassis by rubber between the motor itself and what seems like a piece of hard plastic drain pipe.

 

[Nanook]

on vibrations...

Sometimes things are made more complicated by engineering. If this were my tt that I had pulled apart, I'd find a way to simplify all that B.S. from the motor. Just a motor, no outer "can", no PVC pipe, nothing. Think about it.

The rubber wrap, vibrates. It touches this outer piece of PVC which attaches to the chassis. So the chassis vibrates...if the chassis vibrates, it will send some vibration back to the motor and it's housing. And that will vibrate (and the cavity can amplify that vibration...). and then the pulley, et al.

I don't know this for a fact, but I suspect that mounting the motor as rigidly as possible to the chassis, while removing the extraneous parts will reduce vibrational noise by orders of magnitude.

 

[R-K Rønningstad]

Thank you for your thoughts. I'll consider it all. But I'll try to avoid creating too much work for myself. ��

 

[Ziggy55]

RPM

Do you know the RPM of the motor , mine have a bad bushing, do you think it is possible to replace the bushing ? Thanks for your help

 

[R-K Rønningstad]

Sometimes things are made more complicated by engineering. If this were my tt that I had pulled apart, I'd find a way to simplify all that B.S. from the motor. Just a motor, no outer "can", no PVC pipe, nothing. Think about it.

The rubber wrap, vibrates. It touches this outer piece of PVC which attaches to the chassis. So the chassis vibrates...if the chassis vibrates, it will send some vibration back to the motor and it's housing. And that will vibrate (and the cavity can amplify that vibration...). and then the pulley, et al.

I don't know this for a fact, but I suspect that mounting the motor as rigidly as possible to the chassis, while removing the extraneous parts will reduce vibrational noise by orders of magnitude.

Maybe this is a case for the direct drive turntable. Motor and tonearm fixed relative to each other.
Maybe all this belt drive things are a caused by American and European turntable manufacturers being unable to make direct drive turntables. Except for the Dual 701 and players like the Goldmund Studio (with a JVC DD motor!!).
Oh, well. My Delphi is still not speed stable. Maybe the ebay turntable belt was not good enough.

 

[Nanook]

still speed stability problems?

Hi,

Maybe this is a case for the direct drive turntable. Motor and tonearm fixed relative to each other.
Maybe all this belt drive things are a caused by American and European turntable manufacturers being unable to make direct drive turntables. Except for the Dual 701 and players like the Goldmund Studio (with a JVC DD motor!!).

Not necessarily. There are ways to remake a DD tt into something that will shame so many others. A DD Oracle? it could be done. Or at least a rim drive.

Oh, well. My Delphi is still not speed stable. Maybe the ebay turntable belt was not good enough.

Sorry that you continue to have speed stability issues. The Delphi was/is a wonderful tt and is superior to my old Alexandria in all ways. Please PM me with your direct email and we can try to resolve this without filling up the forum. Once resolved, then perhaps we could post the solution?

I do know that origin Live DC motor kits apparently work on the old Oracles...

 

[R-K Rønningstad]

At the New Year's Day 2017 I installed a new belt, aided by the Oracle Belt Installation Tool and a pair of examination gloves.
So I would like to share the status with regard to my Oracle Delphi 3 problems.
That helped a lot. But still, it comes up at different speeds each time. E.g. maybe a little above or below 33 1/3 each time. Of course I first adjusted the speed with those hopelessly located trimming potentiometers, to exactly 33 1/3 and 45. (It is not 100% stable, but it is kept within the "green" area using the iPhone RPM tool, v1.7.1 by Philip Broder.)
I have purchased another motor, so the next step will probably be to try that, even though the problem maybe more leads me to suspect the electronics.
BTW Nanook gave an example in post #7 on the ratio motor speed (pulley)/platter. Is that speed 588.23 rpm the real Oracle Delphi 3 motor speed, or was it just an example?
And A Happy New Year to everyone!

 

[R-K Rønningstad]

Delphi 3 speed pot meter front panel

Here is the Bourns 3386 2kOhms pot meter located at the front PCB at the panel containing on/off and 33/45 switches. See also https://www.bourns.com/pdfs/3386.pdf .
This is a cermet high quality pot meter. I am unsure about the gain of replacing this. But I wanted to show you the pictures as I have opened the front panel.

 

[R-K Rønningstad]

Oracle Delphi 3 front panel PCB etc

Here are the rest of the pictures i took when opening the front panel of my Oracle Delphi Mk 3.
The small lamps are from Chigaco Miniature Lightning model 7387 and can be found at Newark if someone is in need. These provides background light for the Oracle logo.
The LEDs indicating 33 1/3 or 45 is yellow and located to the right off the two buttons (which may hang if the small panels comes to close to the buttons).
The PCB itself is labelled Oracle 8702.

/RK

 

[R-K Rønningstad]

Pot meter and oil

Here is the Bourns 3386 2kOhms pot meter located at the front PCB at the panel containing on/off and 33/45 switches. See also https://www.bourns.com/pdfs/3386.pdf .
This is a cermet high quality pot meter. I am unsure about the gain of replacing this. But I wanted to show you the pictures as I have opened the front panel.

I changed the Bourns pot to a TT Electronics 72 series pot meter, also cermet and also 2kOhms. No change.
I then again cleaned the platter shaft and the bearing. Made sure it had a sufficient amount of oil. This time only the Liquid Bearings oil, bought on eBay. Checked the friction by holding the bearing with my left hand giving the platter a good spin with the right, and it turned many rounds and for a long time. Reinstalled and started the motor. Just had to turn the speed down, at stable it was, and is. I really hope it will keep its speed correct over time.
BTW the rear located "33" and "45" pot meters are hopelessly located on the Mark III at least. Behind and slightly underneath the platter.

 

[7dage]

Hi guys,
Bought an mkiii where for some reason a previous owner modified the motor. The motor stands separated from the player and as far as i can tell the original electronics are moved to an external box. The previous owner sold it because of a failing connection between the panel at the front and the external box. I have repaired the connection, replaced the small lamps and everything works. My only problem is that i cannot get the speed adjusted right. All potetiometers has a small impact on the speed but at 33rpm it is always running too fast. At 45 rpm it seems more in line but i have not measured it accurately.