Questions?

Happy to oblige with the preliminary front panel drawing...

Final artwork being approved. Metalwork to follow.

Allegedly taking the transformer out, extending its wires, placing it in some sort of enclosure for obvious safety, makes a "great improvement".

Here it is in the flesh...

Beautifully simple!

I don’t suppose it is that simple.

I have mine running my (upside-down) Rega which is currently fitted with standard motor and its  230V pcb.

The 13A plug was changed for the 3-pin "mains" DIN plug which is supplied with the Groove-Runner (it's the type of plug used on a few other turntable controllers and is commonly found on Weller soldering irons). This plugs into the right hand socket and has a locking mechanism. Only the "live and netral" wires are used.

The Groove-Runner is powered from a tiny inline switched-mode 15V DC power supply capable of much more current than the Groove-Runner needs. Its DC plug connects to the left hand socket.

Because the Rega motor uses the 230V board the Groove-Runner output voltage control has to be at maximum, at which it is outputting a measured 113V AC on-load (110V nominal).

The Rega starts up without assistance with the Groove-Runner set to 50Hz and 33.1/3 rpm (surprisingly).

Start it on 45rpm and it tries to run backwards. Not surprising if you understand the 230V Rega board. But a little hand assistance gets it running clockwise OK. Either that or start it on 33.1/3rd and switch it to 45rpm.

If the Manticore Mantra uses the same motor and a similar pcb to the Rega it might run the same without modification. However, a "bag of bits" will accompany the Groove-Runner and instructions will be given as how to modify the sandard Rega motor - and other motors - to run on 110V nominal, and down to the 90V minimum of the output voltage control.

Information will eventually be published here in greater DIY detail.

If you can see the motor it should have one of these part numbers:

9904 111 31813

or

9904 111 31819

For the technically minded here's the block diagram...

That looks great Graham.

As there is a lot of work in preparing it as a kit I thought about offering it ready-built at first. There will be some DIY even with the ready-built unit, that of connecting it to the motor - it will be supplied with

a length of 2-core mains cable (of RP3 quality...);

the outlet plug;

a 4-way terminal block;

0.1uF; 0.12uF; 0.15uF; 0.18uF and 0.22uF mains rated phasing capacitors;

2 x 3.6k resistors to be soldered in parallel for use with the 9904-111-3104 motor (if used).

Or if you have a 230V RP3 there is a possibility of only needing to take off the UK plug and soldering on the outlet connector. Mine starts on 33 with output control up full, and to run at 45 start on 33 and when up to speed flick switch to 45.

Further details (better description)...

The Groove runner is a precision fixed four frequency power supply/drive for belt drive synchronous turntable motors.

Ready built: £370; kit version: £310.

Next post I will discuss the motor phasing kit.

I wonder if it would work with a mark one or two GyroDec with the original ac motor. Do you want to borrow my Papst ac motor to try it out with the Groove Runner Graham?

The regular wiring for 110V 60Hz Rega turntables (as far as I can make out) is for R1 and R2 parallel value to be a single 3.9k power resistor (no need for it to be as big as advertised on eBay); R3 and R4 zero (wired through); and C1 0.15uF. This works fine at 60Hz which gives 33.1/3 rpm on a 60Hz turntable (and even works fine at 67.5 Hz which is for 45 rpm on a 50Hz turntable), but at 81Hz which is for 45 rpm on a 60Hz turntable it peaks too high. The happy medium is given in the 9904-111-31813 "Rega" motor values above, and below is the waveforms for 45 rpm on 60Hz (81Hz in reality) output set at minimum.

Here's the wiring for the 230V Rega, and beneath it you can see the waveforms it gives at 50Hz and 110V.

ERROR!

Above I said start and run on all four frequencies for the 9904-111-31813 "Rega" motor values: it will not start on 81Hz (45 rpm on a 60Hz turntable), but it will start on 33.1/3 rpm (again 60Hz) and by switching through "stop" to 45 rpm it will accelerate up to 45 rpm and run.

It therefore starts and runs at 50Hz, 60Hz and 67.5Hz settings.

Hope you're following?

PS. the scope voltages in the images should be multiplied by a factor of 10 (divide by ten scope leads were used).

It would be good to see some spec's. It obviously runs on 230V but might not on 110V. What size phasing capacitor, and are there any other components? And is there a power rating on it?

PS. would it be possible to press one of the known motors above into service on it?

Those plots look fantastic, especially if you’ve ever seen the waveform from a Li*go or Val**lla. I’ve always thought that this is the reason people love their Arma**don supplies so much, a cleaner sine wave.

You’ve made us a variable speed Arma**don with locked frequencies. When can I at least try one?

Regards,

Chris

Have I really?

Bet it doesn't have the power output of the Arma**don, but then again, these motors will only take what they require, and it can do at least twice that.

I'd better tidy-up the PCB artwork and have some idented boards made then.

Ta.

That’s not a circuit I’ve seen before on one of these little motors. 

I have three instances of the circuit (can only find one right now - typical!) and here is a photo I just took of the board, showing the values indicated in my diagram. I'm quite fussy about getting my facts right in public, otherwise I'd be in dangerous territory, and I was employed in reverse engineering for part of my career, which I have to thank for at least some of my knowledge.

If this was a decent sized motor I’d say you’ve got an odd order harmonic affecting it hence the dip in the waveform. It looks like Rega have added reactance to the circuit to try and control it when powered from the mains. The harmonic could be due to driving the magnetic circuit into saturation.

I may have got my numbers wrong but the standard drive circuit for this motor looks the same as all the others a resistor and capacitor. May be worth trying this circuit rather than the Rega one as the transformer you’ve fitted won’t have the same impedance as the mains supply.

Looking at the data sheet for the motor  tel:9904-111-31104" rel="nofollow - 9904-111-31104   (Farnell 147876) it just needs a 0.1uF cap between the windings.

Ernie wrote: May be worth trying this circuit rather than the Rega one as the transformer you’ve fitted won’t have the same impedance as the mains supply.

Obviously not, but then again it isn't so high as to cause all of what you see. I have been using the (R and C) circuit you refer to for most of the trials (first circuit previous page, a number of different permutations over close to a year) but have never witnessed any motor having an effect on the output impedance of the transformer or the waveforms. And that included wiring it in series which is higher impedance to obtain 220V, to drive a 3.6 watt motor which stressed the transformer near to its design limits (case gets a bit hot too). Also, the transformer was developed special for the job so doesn't exhibit the same limitations as a mains transformer in reverse. It runs significantly cooler too.

Re your edit, the added (series) resistor for higher frequency use is shown here: https://www.mclennan.co.uk/datasheet/1565" rel="nofollow - https://www.mclennan.co.uk/datasheet/1565

As 3/4 of its intended use is at 60 - 81 Hz I considered it a better choice than just having the 0.1uF capacitor. It also runs well at 50Hz, especially as the motor is operating on half intended voltage. Plus it will start and run at minimum output which is just below 90V. It is incredibly quiet in operation and starts up in the same time as a 31813.

Also please understand that the Rega scope waveform was just an observation, and I only included the original circuit as part of the explanation that the Groove-Runner is able to drive the 230V version unmodified (at least the one I have), which might be a plus point to somebody contemplating a purchase.

Hope you don’t think I was criticising your work. Rega have obviously done a lot of work on their passive supply to get the best out of this motor and fair play to them.

I wonder what the scope would show with the Rega circuit (or the other circuits for that matter) connect to the mains supply.

Btw just notice the scope readings show the frequency to 4 decimal places all zeros. You certainly go to some lengths for us don’t you!

Ahha, the scope and its decimal places... wishful thinking but it will go no lower than 10Hz resolution. But my AP is a different story:

I didn't think you were criticising my work. It's only right that I should be questioned or nobody will ever learn anything from these posts and topics. It's good for understanding what things do.

I don't pretend to have exhausted every possible measurement simply because in my mind electronics aren't as exact as some would like to believe. But then again I suppose I take some things to their extremes...

As an example, I'll be hopping over to the 70s amp topic shortly because I'm not satisfied with the power amp quite yet. The bugger is keeping me awake

Jon: I considered that and was considering a Premotec motor with the phase adjustment to minimise vibration. Then I started to look at DC motors and went that way.

From what John C tells me, a turntable manufacturer will be trialing a sample batch as soon as he gets them built. The main delay at present seems to be the output transformers.

If the response is positive we will place it on sale on the forum. The reason it hasn't been offered so far is due to the limited interest in this topic. There seems to be only 3 potential sales

I also don't consider it could be a general sale item because it requires a little more understanding than a plug-n-play item. Even if supplied fully built the user will need to at least change the turntable plug. Everything these days has to be fitted with a plug, so the Groove-Runner could only be legally sold to a DIY'er.