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What's the matter with my Michell Mycro turntable?

Posted: 11 Jan 2004 19:19
by trevitup
I got the table used; it came with a Mission 774 tonearm and a Sumiko Bluepoint Special Cartridge. It arrived very clean and well-packed. The motor seems to run too slowly; the LPs I've tried really, really drag (in fact, the speed is about right for an LP on the 45rpm setting). We've adjusted the tonearm and cartridge pressure ad nauseum. I don't have a record clamp yet, but I don't see any album skidding. Is the motor just bad/worn? Or is there a less painful, expensive solution? Thanks for any suggestions...

Posted: 11 Jan 2004 19:48
by docjowe
hi
Have you checked for oil in the platter bearing; it is essential; search the forum for lubrication thread.
docjowe

Posted: 11 Jan 2004 20:18
by JaS
Are you absolutely sure the deck is running slow? There are strobe discs in the tools section to check this out. Also is it stable but slow or is the deck also suffering from excessive wow?

If it is the 33 rpm setting that is bad then it could be the belt slipping due to streching with age. When the belt is on the smaller 33rpm pulley any slackness will be noticed that may be taken up by the bigger 45rpm pulley. If the motor isn't noisy then this is the first thing I would check, and you could try cleaning the belt to see if this helps. It may also be worth seeing if the motor can be moved further away on its mountings to take up any slack but this isn't always possible :?

Regards,
JaS

Posted: 11 Jan 2004 20:56
by NeilM
I don't know Michell decks, more's the pity, but.

If your competent with the ol 'majic lectric stuff' I would also get busy with the test meter. Michell will tell you what voltages you should have where. If the deck has a psu, you might have lost some of the smoothed out voltage.

You also don't tell us where you are located. If you in europe, then 230V should be ok, if your Stateside, and you have a Uk model, you can't run 240v gear well on 110v!!

Just a couple of thoughts, working, in my case, from a position of complete ignorance :shock:

Neil

Posted: 11 Jan 2004 22:00
by trevitup
Thanks to all of you for your responses.

NeilM: I'm located in the US, in South Carolina. But the seller was also using the table in the US (Washington State), and it seems to have worked well for him.

JaS: Yes, I'm sure it's running slow - it's not an in-and-out, "wow" type of problem. Also, I just tried a 45 record, and it's just as slow, proportionately, as the 33 1/3 setting. The motor runs very quietly, and as far as I can tell, cannot be moved to firm up the tension. Can the belt be cleaned with soap and water, or is something fancier required?

docjowe: Yes, there seems to be enough oil - the plater will spin almost endlessly once underway.

Posted: 11 Jan 2004 22:51
by NeilM
OK, so we assume your man in Washington State is a pukka chap. Therefore something has been altered in transit.

As you are in the good ol US, then has the power supply got a 240/110 switch, or a jumper link which needs to be in for 110v position. A bump could have altered this.

Failing that, has the motor taken a knock, any obvious signs of contact, or possibly any of the wires been strained or wrenched, beaking a connection.

Has anything moved, which is now touching the platter, or maybe the motor shaft :?: :?:

I'm not sure on the best process for cleaning the belt, but any contact areas for the belt, made of metal, go over with a cloth with a little degreaser.

My guess is, something has moved in transit, and it's just a matter of finding it. Sorry, a bit obvious.

Neil

Posted: 11 Jan 2004 23:02
by euclid
I am not familiar with this turntable. I went to the library and found a link that leads to some very useful information on mitchell turntables. A lot of the material is about the Gyro Deck but you will find valuable information on the Mycro and other modles that appear to be related to the Gyro Deck. one of the links leads to http://www.geocities.com/michell_gyrodec/ Read the entire page. The other two may have some more information.

From the information that is on those pages I suspect you have a DC motor without any sort of speed regulator. If this is true, the motor speed will be very dependent of the power supply voltage and friction. There should be a voltage adjust trimmer on the power supply. You should adjust it for the correct speed. Also check for excessive friction and a prpperly oiled bearing.

Posted: 11 Jan 2004 23:07
by JaS
Hi,
The belt could be cleaned with soap and water but I've always found a little isopropyl alcohol (tape head cleaner) leaves belts and pulleys 'squeaky' clean and it evaporates pretty fast too. However, I would expect a slipping belt to cause noticeable speed fluctuations and this doesn't appear to be the case?

If the deck has an A/C motor then speed is governed by the mains frequency and the voltage coming from the power supply isn't crucial. In this case you need to look at the mechanical side of the deck; is the record slipping on the platter (speed instability); is the belt slipping (speed instability); Is the bearing worn? is the pulley the correct size? This last one may sound unlikely but if the deck has an A/C motor then Michell may well have fitted a different size pulley for the US market and these aren't always subject to the sort of QC they should be :?

If the deck has a D/C motor then the voltage has a direct effect on the running speed and there may be adjustment available inside to calibrate this? As Michell has used both A/C and D/C motors in its product range the type fitted will need to be accertained from either the motor or power supply markings.

Regards,
JaS

Posted: 11 Jan 2004 23:11
by JaS
Oops sorry for repeating the DC motor advice, Euclid must type faster than me!

I know UK market Mycros have an outboard supply so hopefully this is a DC supply as speed adjustment is usually easier than on AC decks where mechanical faliure or wear is more likely the culprit :wink: Unfortunately Werner's Michell page (see euclids link above) suggests a HFN flutterbuster as an upgrade and as this is definately for A/C motors so you may be out of luck.

Regards,
JaS

Mycro speed

Posted: 12 Jan 2004 22:21
by abril
I had exactly the same problem with my S/H Systemdek when I got it - the ball that the main bearing sits on was missing so there was too much friction so it ran slow

Posted: 13 Jan 2004 03:20
by trevitup
OK, folks: First, many thanks for all you've written.

Second, I got up the nerve (I'm new at this, and afraid I'll damage something) to take the bearing assembly out of the spindle shaft. I found a) that the well was almost dry, and b) that there was a small empty hole, roughly BB-sized, sitting offset to one side, that I'm assuming is supposed to hold what Michell calls the "thrust ball".

So, will any old household oil (eg, WD-40) work? And, am I right about the "thrust ball"? If so, where can I get a replacement?

Posted: 13 Jan 2004 04:02
by euclid
I don't know this particular turntable but the basic choice of oil in order is:

1) The manufacturer's reccommended oil. They are rarely wrong.

2) Turbine oil (sometimes sold as Zoom Spout Oil by one American hardware chain), or a good grade of Gun Oil.

3) A high quality, medium viscosity oil.


WD40 is too thin for most purposes. Its primary use is as a penatrating oil to loosen up frozen nuts, screws and other such things.

Automotive motor oil should be avoided. It is optimized for high temperatures, not room temperature.


If you are not using the same oil that is in the well, drain out all the oil, clean all the old oil off the spindle and out of the well. Extreme cleaning is not necessary. Just get it clean as you can easily. Many of these assemblies have a ball in the bottom that can fall out and roll away.

Posted: 13 Jan 2004 04:16
by euclid
Another good question is "how much oil should be used?" Once more the manufacturer's reccomendation is first choice.

If you don't know the manufacture's reccomendation the correct answer may be one of the following:
1) Just below the top of the ball
2) just above the top of the ball

It should not be so high that the oil comes over the top of the
center well or leaks out of any vent hole that may exist, when the platter is inserted. I have delt with this type of bearing on turntables by Empire (Audio Empire), RCA Broadcast, Gates (Harris), QRK and Russco. On most, if not all of these, once I started lowering the platter into the hole for the second time after, I could let go of it and it would settle gently into the bottom of the hole, cushioned by air trapped in the bottom. If you try this do it in such a manner that if the platter platter fails the test it does not slam into the bottom bearing.

Posted: 15 Jan 2004 11:21
by Lord_Jagged
The missing ball is definitely your problem. I also have experienced this on an old Systemdek and the symptoms were exactly as you describe. Not sure about the quantity but oil type should be ordinary automotive automatic gearbox oil (ep90) or similar. Try about .8 ml to start with. For your further info Michell Mycros only used ac motors a standard, they were long out of production by the time michell started offering dc replacements. Michells website will give you the history and if you contact them they will provide any other info you need.

Good luck