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Moth 33/45 TT psu - wiring advice needed.

S

Sid and Coke

and so the rebuild continues..
Hello folks,
Well just dipped my toe in the TT psu water again and bought myself a Moth TT PSU. I bought it mainly because i miss not having a 45rpm facility on my LP12 , but can't afford to buy a Lingo (even a s/h one ) at the moment. As you can imagine the first thing i did when i opened the box was take the lid off and see how it's made. I'd say that it looks very 'Clonable' if you had a bit of electronics knowledge. looks like there are only a couple of IC's, one looks like an 8 legged op amp and the other is a 14 legged thingy, all the rest of the components look like the normal run-of-the mill type , eg resistors, caps, transistors and diodes.

OK back on track now.
Basically as far as Electrical inputs go this PSU has an IEC inlet socket ( nice and simple so far), but then it has a 3 wire mains flex as an outlet. The LP12 motor has effectively 3 connections; the red and blue and 2 x greys.
Do i need to put the Live wire ( out of the Moth PSU), through a network ( ie Geddon clone) to split and stagger the single phase input into 2 out of phase waves ?

I'll post some piccies on my website so you can take a look and advise. This item didn't come with any instructions so I'm not gonna touch anything before i have all the gen. I think it might have been sold as a Moth ' Flutter-buster' some years ago but don't quote me on it.

There where quite a few bidders on it so if it doesn't work out I'm sure I'll be able to pass it on without losing too much dosh for the experience, one of the advantages of buying 'reasonably' priced gear off e-bay.


Thanks again.
S&C.
Here's the piccys:-
Sids 'new' TT psu
 
Very interesting, Sid!
I would imagine that the 3 wires are actually the equivalent of the red, blue and grey - i.e. they're already set to give the out of phase stuff. Can't be sure though, and I'm not sure how you'd test it without biting the bullet and attaching it to the LP12. Can you at least measure the voltage coming off the leads?
 
Hi Richard,
It is the fact that the output wires are just like a 'normal' mains lead that is throwing me a little. ie they are Brown (live), Blue(neutral) and Green/Yellow (earth). this makes me think that they should be wired in just like a Geddon clone, with Earth to the LP12 Chassis, Blue to the 2 x greys and the brown to the Red and Blue LP12 motor wires, but i'd then need to still split this single live phase into 2 but do it using capacitorss to make one of the split phases lag, as i think that the LP12 motor is an AC syncronous, 2 phase device.
please feel to correct me anybody, if I'm way off the mark.
Right time to get the DVM out.......
 
I'm not sure from the photos but that iec socket looks like a panel mount socket which would accept a cable mount plug. This plug wouldn't usually be connected to the mains as it has exposed pins. Normally you'd have a panel mount plug with a cable mount socket.

just wondering if the captive lead is in fact the mains lead with 3 pin plug removed and the iec panel mount socket is for subsequent connection to the turntable. Need to check inside connections to make sure
 
Well spotted that man! I think you may well be right there - if you look at the "inners" pic, the wires go to the top of the board, where there is a fuse etc, so that suggests they are actually the incoming power (obviously tracing the PCB tracks is needed to confirm).
Also, the wires leading to the socket are not "mains" colours, which suggests that the socket is, as Tim said, the output rather than the input.
 
I know you wont believe me , but this is true. I took a closer look and was thinking exactly the same thing myself :D . I came back here to say as much and lo-and behold two other great minds had beat me to it !

Basically i popped the circuit board up just to trace the wires and check its condition before i powered it up. It looks like I'm not the first 'careful owner' and that over the years a few minor repairs have been carried out, nothing too heavy though.
I think I'm going to still hang fire before it see's any wiggly amps just yet.

Any views on Phase shifting/splitting ?
 
I wouldn't have thought phase shift would be necessary - surely the thing should just work as is. There are two explanations I can think of for the 3 wire output. Either....

there's no earth wire for the LP12 chassis, and the 3 wires are one for the motor red wire, one for the motor blue wire and one for the two greys. or...

there is an earth wire and the other two wires are dc outputs for a dc motor

Could check with a meter or do a 'Help please Andy' post
 
I would definately check the output with a meter before letting it anywhere near the deck. To my mind, as the output looks like a standard IEC socket, I'd half expect to get mains voltages from it.

It's for exactly this reason when I build a geddon clone I'll use a non standard output connector on the box. It saves confusion.

Mick
 
Thanks for that Tim,
I suppose i'm just thinking of how my single speed DIY Geddon is wired up.
Basically with the Geddon the two grey wires are connected to Neutral, then the live is split into two, one of which goes straight to the Red wire , the other one is connected to the blue wire but it has a 0.2u capacitor in series to give a phase shift between the red and blue. ( i think ;) )
I think that looking at the Moth psu the only difference with it and the voltage output of the Geddon is that the freq of the voltage will be different to change the speed of the syncronous motor.
:confused:
I sometimes wish i had an old practice LP12 motor to practice on

Mick:
The Stainless steel locking DIN i used on my Geddon seems to work a treat. see here : Sids geddon connections
 
I think you put mains in and you get mains levels out. So you'll need the phase shift stuff in the turntable. IIRC the idea was for this to work with all sorts of synchronous turntables.

And that IEC is definitely an outlet. The whole construction looks a little dodgy to me, take care....

I think 'domfjbrown' got one of these recently, perhaps an email would assist.

Paul
 
Sid

There is a little information here which may explain the modifications you are seeing on the board. See the section headed 'Improving the Flutterbuster'.

Mick
 
Mick,
It has Flutter Buster etched (in solder) on the glassfibre circuit board so i assume it is one and the same.

Paul,
I've been in touch with Dom privately over the last week , regarding this item.
I think Dom is using his on a Rega Planar 3. Seems to think it works quite well. It'll be a good bit of practice if i have to build another Phase shifting splitter circuit. I'll need to buy a female IEC socket anyway so I can wait a while longer, to see what else i need to buy.
I can see this can of worms spilling over ......


Anybody happen to know if the Linn and the Rega use the same motor unit ?
 
First off, apologies if you think i'm kicking the crap out of this thread. I'd just like to try and make sure before I fry anything.

OK here goes:
Fitted a plug to the fixed lead and probed the soocket outlet ( i was a bit scared ;) and expected puffs of smoke).

First off nothing !!! thought i'd been sold a dud and so went out for a walk with the mutt, grumbling and swearing to myself.
During the walk - bing ! the light went on. Its OK supplying the thing with power Sidney , you also need to toggle the switch and actually turn the thing on ! ( muppet :rolleyes: )
Rush home and try it out - bingo. Only trouble being I'm getting two different voltages.
The box outputs 230+ vac on one switch position but only 200 vac on the other. I am using a Digital Multi-meter. I figure that my meter is calibrated to read AC voltages at 50 Hz but that if this new PSU is giving out 230vac at a higher freq than this ( for the 45 rpm facility) then my meter may not read accurately.
Sorry about this but I've just completed a short 2 week Electrical Fundamentals course for an Exam i have in 4 weeks time, I'm probably thinking too much at the moment ( a little bit of knowledge and all that ).

Comments?
 
I would be surprised if your meter cared about that range of frequencies.

AFAIK the Rega and Linn use the same basic motor.

Paul
 
Hi Sid

I think I understand what the thing is doing now. If I'm right, set at 33rpm it's giving a 50Hz voltage. At 45rpm, I read the figure needs to be 67.5Hz so I presume that's what it's giving, both though at fairly close to mains voltage.

If that is the case, you'll still need the voltage dropping resistor and phase shift capacitors. Perhaps they came on a separate board which was supposed to be fitted to the LP12 to enable use of the Moth supply.

Looking at some elementary VIR stuff, and I don't mean that to be patronising; I'm just relearning it myself, I think the resistor value needs to be in the region of 15-16k. I'm basing this on the impedence of the motor which I read was 8.8k pulling a current of 8mA. That should give you ~75V at the motor on 33rpm and ~83V at 45rpm, taking your measurements of 200V and 230V respectively. I agree with Paul about your meter; I don't think it would care about AC frequency. My meter manual doesn't mention acceptable ranges for such things.

Food for thought I hope. I'd be interested to get confirmation of the motor impedence and if anyone has measured the current it draws.

Mick
 
I would be surprised if your meter cared about that range of frequencies.
Click to expand...
Oh well Paul, It was just an idea.
Maybe then the circuit drops a little voltage whilst converting the 33 rpm 50hz ac to the higher freq required for 45 rpm ? I'll try my Anologue AVO meter on it tomorrow and see what that does.
It would seem that the best way that i can incorporate this new thing into powering my Linn, is to power my Linn off the geddon as it is now , but power the geddon off the flutterbuster. That way i'll get the step down and phase shift from the geddon and the frquency change from the flutterbuster.
Hmm a bit of an ugly solution, :( , perhaps i could put it all in a bigger box :)
 
Perhaps they came on a separate board which was supposed to be fitted to the LP12 to enable use of the Moth supply.
Click to expand...
In general an LP12 to which you would consider adding a Flutterbuster would have a mains plug on the end and would have the necessary stuff internally. I imagine that it wasn't intended for Valhalla or Lingo TTs but to upgrade old LP12s and the wide range of other turntables using synchronous motors, from Rega to Heybrook via Manticore.

Paul
 
hmm I see what you mean Paul. I would imagine that this would have been an ideal upgrade for my old Systemdek iiX with its simple PSU installed in the plinth.
I had decided that I'm going to use the Flutterbuster to power my 'Geddon' at the 33rpm speed setting the geddon will be receiving pretty much what it does at the moment, circa 230vac @ 50 hz. On the 45 rpm setting the Geddon will be supplied with circa 200vac at a higher freq ( is it 67+ Hz???) , will this rise in frequency have a detrimental effect on the Phase shift, will I have to change the value of the geddons capacitor.
the more i think about this little mini project the less scary it becomes :(
 
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