Rega motor control board…

[J!m]

So, I have the last pieces to get my “R-3” table together and the motor is acting up. I though I had a bad trace because it was acting like a bad cap- hard starting and can run backwards.

Did some testing today, and I have 45v on each “phase” (either side of the cap) and I think it should be higher voltage. Dropping resistor is new also, and correct value (per specs). I think I should be around 90v and I thought I did, but each phase us measuring g 45 and perhaps each phase should be 90?

Any ideas?

 

[J!m]

I have an idea.

The motor is rated for 110 VAC and I have reduced the voltage (or rather, Rega did) to about 45 volts.

I am going to try bypassing the dropping resistor and see how the motor runs. I was hesitant to do that, as I wasn't certain of the motor design voltage; now I know that. I may need to add a parallel resistor, to increase the voltage, as I feel it is still too low for reliable operation. But, it does run well with the platter on there with a little "help" to get going.

If that works as I expect it will, my plan is to add a time delay relay (solid state), which will provide full line voltage for 30 seconds or so, to get the (significantly heavier) platter up to speed, and then drop out, to run at reduced voltage for less cogging and noise- the original intent of the Rega scheme of dropping the supply voltage. Best of both worlds. Maybe.

Relay is $65... I'm going to check the local place, because they are (unfortunately) going out of business and (fortunately) have major discounts ratcheting up to the end of November, when they expect to close down for good.

 

[George S.]

Standard procedure on a old AR turntable is turn it on and give the platter a push to help get it up to speed. Don't know if others were similar.
Read somewhere that leaving the cap off the motor allows the motor to run reverse as well as forward depending on the direction of push.
My AR XB will start from a standstill with no push because it has a later model motor but it's a very slow start. A simple record cleaning brush really puts a load on the motor and slows the motor down.
Have to wonder how the Rega behaved when new.

 

[J!m]

Yes, the cap is needed to define rotation, so that stays. Bad caps do the same thing, and why I offer a rebuild kit for these. But with the much heavier platter, the motor just can't get it going and asking someone to "jump start" the platter just wouldn't be Cricket as they say.

And the Rega (before mods) did benefit from a push to get going. I suspect AR did the same trick, or Rega stole it from them...

I think I can create, for less money, a time-delay situation to do the same thing for less than $60, but I'm trying the store later today anyway.

 

[J!m]

So, today I went for it and bypassed the dropping resistor. Much more torque now.

But what’s “funny” is that it still can run backwards. I guess the brushes are shot and the motor needs to be replaced, but it’s not acting nice these days. It it not openable to service…

I soldered a wire bypass on and I’m putting it together for further testing.

One thing is the motor pod works nicely. I had the motor directly on the u set side of the plinth and it sounds like an electric toothbrush. In the pod, the vibration is much less. Not totally gone, but much less. The pod rests on the bottom-most layer of the sub-plinth, so it should be isolated from the wood plinth.

 

[J!m]

Oh, the dropping resistors for the LED is as hot as hell. Confirmed with calibrated finger.