Well, this is my first post so please be gentle! I’m a Naim fan through and through but I also love the Michell Gyrodec and thought I would start my first contribution with a solution to a problem rather than a request for help…
I recently tried my first foray into MC cartridges on the Gyrodec, and having swapped the cartridge over, sat down to take a listen. The sonic differences were somewhat eclipsed by a nasty cracking sound whenever a record was removed from the table, that seemed to upset the 282 greatly, putting it into overload protection mode with a temporary mute imposed. I swapped back to the original cartridge, thinking this was the only thing I had changed, only to find the same problem! To cut a long story short, I spent much time probing around with a multimeter and established that there was no electrical continuity between the platter, bearing and the metal sub-platter. Further investigation revealed that just a little bearing oil had tracked out of the collection well and down the threads between the bearing and sub-platter interface. Recalling how just such an oil tracking issue is well known to kill the Defender TD5 ECU wiring loom, I dutifully cleaned all the threads and rebuilt the bearing. Presto! Static crackle gone and normal sonic heaven restored!
I have not come across any mention of this here or on any other vinyl enthusiast forum so thought it could be of use to any Gyrodec owner, struggling with earthing issues…
@mij29
I’m a Linn LP12 owner myself and have no real wish to ever change… but I have always had a hankering for a Gyrodek. Probably the best looking turntable…in the world (in my best Jeremy Clarkson voice)!
Nice system there.
Hi, yes exactly, the oil had slowly tracked down the threads and there was just a film at the bottom edge of the bearing flange, indicating that it had tracked across all of the threads used to hold the bearing secure. A multimeter indicated that there was a completely open circuit if touching the spindle with one terminal and anywhere on the sub-chassis or the three inch earthing strap for the armboard with the other terminal of the multimeter. As soon as the oil was cleaned away, all connected metal parts of the deck were back in electrical continuity and the static generated by placing or removing records could travel down the phono earth wire to the phono stage ground once again.
There really is very little room for error filling the bearing well with oil; Michell say to add just 2mm into the base, but this is hard to see with the oil’s meniscus. If its too much, the brass base of the outer part of the bearing (connected to the record spindle) displaces the oil up and onto the sub-chassis when it is lowered into position, and then the oil is able to track down the bearing threads with ease…
It took a while to find the problem, as all I had done was remove the deck to a desk to carefully work on the cartridge swap and I never touched the bearing, it must have just coincided with the oil finally covering all of the bearing threads. Oil is totally hydrophobic and is an excellent electrical insulator in these circumstances…
Whilst I have removed my platter a few times, I’ve never added any oil in the 5 years of ownership. I have simply assumed that what was filled from day 1 is there. Michell don’t suggest checking or any real maintenance of the bearing or its oil.
I can see that over filling would give the problem you described. Albeit one that would take time to find. Clearly clean, oil-free threads that ensure continuity are essential. Hence, I’d expect some some of suggestion from michell to routinely ensure this!
Certainly; I purchased the deck direct from Michell during the first lockdown and hence I had to install the bearing oil myself as the deck was built up. There was no mention of the risk of bearing electrical insulation but I guess until it happens, nobody knew that it could actually be a problem!
Thank you mij29.
I have recently bought the Perreaux 255i amp and encountered the exact same issue myself. The amp would perform perfectly and then out of the blue I would change to another record and when the metal clamp touched the spindle the amp went in to PROTECT! mode.
I “topped-up” the oil in the bearing well only a few days ago and had suspected that I had put too much oil in because when I replaced the brass bearing housing there was an audible bubble noise.
When I followed your instructions this morning I discovered an excess of oil on the face of the brass housing and the threads you described also coated in excess oil.
I’ve cleaned it all up; reduced the oil depth to about 2mm and will experiment during the day.
If this doesn’t work my only solution will be to touch a radiator in order to discharge any static before I use the turntable.
That sounds exactly the same and I’m sure the problem will have gone so long as the threads on the bearing to plinth interface are nice and dry again. I could a very basic multimeter invaluable to check this, just by touching one end to the spindle and the other to the ground post next to the arm board. I’d be very glad to know if it works for you!
Very useful post - I had Michell increase the lead length between the HR power supply and my Gyrodec, and after setting things up starting experiencing serious static after playing an LP. When I came across your post it clicked - I’d removed the platter to refit the motor and must have dripped a bit of oil - after cleaning all solved. Many thanks.
Funny thing is, the HR psu is sold as being better than original AND you can adjust the speed. But, you can adjust the speed with original psu. The pot is inside.
Bought a simple multimeter to do as you suggest. It has a buzzer to indicate continuity. The 3 inch earth strap is attached to the underside of the tonearm base and the underside of the chassis. I disconnected the strap from underneath the chassis leaving it attached to the tonearm base. I then touched it and spindle with the multimeter and there was no buzz. I touched each end of the earth strap and the meter buzzed; so it’s OK.
If I understood you correctly this indicates a disconnect of some kind or am I simply doing the wrong thing? I am not technical in any way and tend to do things by numbers rather than from knowledge.
Hi, excellent, the multimeter is a super helpful tool. I too am minimally electronically minded, but I love to be able to fix issues like this myself - a major part of the reason I sold an LP12 that would always and evermore need tweaking by an expert. Essentially, if the main bearing thread is nice and dry and free from bearing oil, then there should be electrical continuity right across the plinth and up through the bearing to the top spindle for the record. So you should be able to touch one end of the multimeter to the spindle and the other end anywhere under the plinth that is not painted and get the buzzer sound of electrical continuity. That is why I mentioned the earth attachment point as this is definitely electrically connected to the spindle when all is well. So you do not need to actually disconnect the earth strap at all and you should hear a buzz anywhere you touch on the strap and ergo, the static current will be able to properly escape down the phono cable earth wire to the stage’s ground point and not through the signal wires that make the amp go into emergency protection mode. I hope that makes sense and please post your results!
You’ve been really helpful and I am genuinely very grateful.
I did what you suggested yesterday. I connected the spindle to the earthing point directly beneath the tonearm (I call this the tonearm base) and got no buzz. I then connected the spindle to the earthing point directly attached to the metal plinth underneath and again, no buzz. It really is frustrating.
I did it all again this afternoon just to make doubly certain that the bearing thread was absolutely dry and it was.
My dealer (Audio Emotion) are exceptionally good and I’ve used them for years. He tells me that this is not uncommon on some amps and that I should just touch a radiator before changing records. I don’t think I should need to do this for an expensive amp like this. It’s a puzzle all right!!
