Audio Note TT-1 spinning backwards

[GPHenry]

Hi there, I'm hoping some Systemdek experts can offer some assistance as the AudioNote is a revival or continuation of one of the Systemdek turntables (IIX or IIX-900).

On start-up, the platter has sometimes started to spin backwards. Prior to this, I noticed what seemed to be excessive vibration noise which could be clearly felt through the plinth. The motor is an Airpax 31818.

I'm in Australia where mains voltage is 240V but can easily rise to 250V.

I can see one large resistor from the live mains, then two stacked 0.22uF/400V capacitors. There is a small resistor across the terminals of the lower capacitor. There is then a 0.33uF/400V capacitor which is connected to the motor. Detailed pics below...

Any advice as to what needs to be done or if capacitor or resistor values need to change (to take into account a slightly higher mains voltage in Australia) would be appreciated. I am a complete novice so advice as to whether a DIY beginner could handle this or whather I should just seek out a technician would also be gratefully received!

Cheers,

Greg

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[abril]

First thing to do (easy to do yourself) is check all the connections in the choc block are secure,don't forget it carries mains voltage

[GPHenry]

Thanks abril, just checked that and every thing seems tight and right with the connections. I see you're in Cornwall - what a great spot! I've got relos in Plymouth and we spent a great day in Cornwall on our last trip there.

The large resistor in the circuit is apparently a 2.2Kohm/2W and the smaller one might be 1 megohm 1/4W. Does this sound right? And are these values ok for mains of 240 to 250V?

Thanks,

Greg

[abril]

Very unusual setup by Audionote which I've not seen or heard of before on a Systemdek.
The 0.33 orange cap would be the phasing cap.
There are others on this forum who know these motors better than me.

[willb]

HI GP Henry,

Yours looks like an variation of my mid 90's IIX 900 voltage stepper.
The 2k2 is the same, but Audio Note have tied 2 0.22uf caps together with a resistor across them. they look like decent quality ones (probably polyester) but are only 20% tolerance (the 'M' on the side).

So the culprit is probably the orange 0.33uf which, as Abril says is the phase capacitor. If you replace this with a new 0.39uf or 390nf 250-400v MKP or MKT cap, it should sort it out. This will work a bit better than 0.33 as long as you are on 50hz mains? I know N.America are 60hz, but you guys tend to be like us!
http://www.ebay.co.uk/itm/10PCS-CBB-394 ... f#ht_1948w

Give it a try and let us know.

Cheers

Chris
Plymouth

[GPHenry]

Hi Chris,

I'm glad you chimed in as I've read some of your posts on the Systemdek and you seem very well acquainted with the motor and supporting circuitry. On the weekend, a friend helped me take the various measurements and all caps and resistors measured perfectly. We nevertheless proceeded to replace these with components of the same value.

Unfortunately the result was the same with the motor starting in either direction and under load not being able to get the platter moving at all. Our measurements showed we got a voltage drop from 246V to 115V, so this should not have been the issue. We didn't try a higher rated phase cap but I assume if the original from Audio Note didn't work, nor would a higher rating one. I should also say that under load of belt and platter, vibrations was excessive and clearly felt through the plinth.

So it looks like it could be a problem with the motor. Audio Note UK were great - they sent me the circuit diagram for the turntable which confirms the circuitry is correct (though possibly for 230V rather 245V+ - Australia is 240V but regularly runs up to around 250V). They also sent the data sheet for the later Premotec motor (ending in 13 rather than 18) and said I could possibly try this circuit with my motor (6k8, 2.5W resistor and a 0.22 phase cap).

Tomorrow the Audio Note guy here in Sydney will take a look at it so I've got my fingers crossed. Worst case, I guess it will be a new Premotec motor and some surgery on the pulley and circuit. In this case, possibly a higher resistor for our voltage level (maybe 7k5, 3W?) and I understand smaller resistors in series with each motor coil is recommended (around 600ohm, 1W).

Any views on these values should I need to go with the new Premotec motor would be appreciated.

Cheers,

Greg

[abril]

If you have a DMM disconnect the motor wires and do a resistance check between blue and grey and brown and grey on the motor - they should be the same within a few ohms.

[willb]

Hi Greg,

The one in this link is not very clear but probably is a Premotec. (same factory in Holland but now owned by another company).

You'll notice that it only has 2 capacitors and no resistor - this is how Rega have run these motors for several years now. The 6k8 is replaced by a 0.22uf in series with another 0.22 in parallel. I bought one s/h a few years ago and it measured 240-105-98. Your Airpax is running a bit high, these should run about 87-90ish @50hz.

A used Rega one is a cheaper way of buying one (they come off decks which have had the 24v upgrade package). Just don't buy a Linn one as it'll be nearly twice the price (for the same thing ) Use it as it comes with the Rega board and it'll be much smoother than the old one. Mine runs on a PT export board with an extra cap across a switch to get it about right @67hz/45rpm. Next step up from here would be a dc set-up.

best of luck.

Chris.

PS: Where do your relos live - being nosy


http://www.ebay.co.uk/itm/Rega-Planar-P ... 500wt_1357

[GPHenry]

Thanks Chris. Will see how it goes with the tech today and then make a call on which way to go. The AN UK guy has said the motors are identical regardless of the data sheet on them and still recommends going with their circuit (2K2, 2 x .22uf in parallel with 1mohm resistor and .33uf phase cap. Alternatively, go with the 6K8 or slightly higher, trim resistors and 0.22uf phase cap. Will probably try their recommendations first up and see how it runs. If too much vibration, I can always try the Rega circuit.

I'll let you know how it turns out.

My relos are in Deacon Park, by the way.

Cheers,

Greg

[willb]

I bet you mean Beacon Park! That's just up the road from here...

No, Audio Note are wrong I'm afraid.
The older Airpax 818 and 807 motors are very different. They draw a lot more current and need a 0.39 cap (except Philips told everybody it was 0.68 - don't ask!).

They (AN) do tend to be a bit like this - I need a set of springs for my IIX900 - but all I get is pathetic excuses like they "can't get any" - yet they're still manufacturing the thngs in Estonia or somewhere.

Rega know what they're doing - they've probably made more t/t's than Systemdek, Audio Note & Pink triangle put together - so trust them. They were the first one's to use the '813 motor (which was made as an Airpax branded one originally, presumably by Philips). It is the first and only motor to be made specifically for t/t use - none of the others were, just standard industrial motors which got used for t/t's.

So 'tiz your call, but if AN came round to my place I could demonstrate the differences as we've several motors & psu's between us...

Actually, the very top Rega board has a couple of resistors to even up the 2 phases across the motor and they fit a decent thrust bearing, which is the best version of the 110v motor kit - I'll post a pic if i can find one.

Cheers
Chris.

[GPHenry]

Beacon Park is correct!

Waiting to see what come from the AN guy here in Sydney. Very good guy and seems to know his stuff, so if he puts in the new motor, I'll see how quietly it runs with what ever circuit he goes with before thinking about alternatives to optimise performance and minimise vibration.

Thanks for all the advice and I'll let you know how it finishes up!

Cheers,

Greg