Trade: The Funk Firm
Posts: 72
I'm Arthur.
Close friend to...an accountant. What does THAT say about MY street cred...Originally Posted by Oldpinkman
... I was a close friend of Arthurs .
My original turn of phrase was that I "bat for the other side" - but on reflection, given its Arthur we're talking about,...misinterpretation, so changed it
Senior Member
Location: Deleted
Posts: 6,566
I'm Deleted.
Well I was married to one - also trained as an auditor!
Account Deleted
Posted by Simon (Sq2225917)
"The inter revolution accuracy is indeed very good but take a minute to consider how round it is. That's actually very poor, in fact in noticeably resembles an octogon as opposed to a circle. Pop your platter off and look at the motor windings, how many does it have? Typically that would imply a cogging artefact"
I believe that your approximation to an octagon is somewhat simplistic and does not take into account the calculated mean deviation at all points on the plot. This is where these "tests can be very misleading"
In actual fact the motor system is as follows:
12 Drive coils; a 16 pole radially magnetised ferite magnet: an 8 pole pulse generator; interacting with 3 pairs of sense coils. pulse generator printed circuit which wraps around the coil assembly and interacts with the rotating magnet.
I have not done the calcs to determine what this represents as possible vector position points that could be determined on a plot.
But I bet it will be far more than 8
What magnitude of speed error does the plot represent, it looks all very impressive but the numbers do not tell me anything.
Yep, I got my coils and poles the wrong way round - sorry about that. I even counted the coils
Martin,
The design of the motor control circuit is elegant when you consider when it was first made and there are considerably more than 8 points of input. Can you tell me what the vector units are for your plot and what the vector rotation point is?? Without these numbers surely you would have to agree that the plot does not tell us very much. If it is supposed to indicate speed variation at any angular position then what magnitude of variation are we seeing? 5% 1% 0.01% 0.0001%???? surely you would want to know this.
I personally find the plot very interesting technically, and would like to know more.
Trade: The Funk Firm
Posts: 72
I'm Arthur.
The clue lies in Richard's original post - "...close friend of Arthur's", so I can't have been (and wasn't) serious.
Instant apologies if offence taken...None meant!
Hi Mike
It's all buried in this long thread by Paul R at PFM:
http://www.pinkfishmedia.net/forum/s...ad.php?t=70027
Despite what Simon says, the Technics plot is very good compared with many of the plots in that thread. I agree that the DD motor and control electronics are very elegantly designed.
Looking at the motor, it's a work of art and amazing in a relatively low cost mass produced model.
Banned
Location: Granes - Haut Vallee de l'aude - EU
Posts: 2,830
I'm Richard.
Martin
First, thanks for the offer to hear the Shelter. As you note, a pity you are not a bit closer. I have been a bit preoccupied taking Mrs S in for a retread on her gynae surgery. i think she's properly vulcanised now, but I have been trying to follow all this on my Samsung Galaxy Note which is not first pick for either viewing graphs or flitting between threads.
Can I just check, the accountants , non-engineer take on this? Would I be right in concluding that the (very long) PFM thread establishes a methodology for testing the stability of the drive, establishes that it is valid after a few refinements, and produces plots where "perfect" would be a circle, and wobbles in the circle are bad?
It goes on to speculate about whether it can "see" the faults in the motor in question by counting how many wobbles there are, but this is inconclusive. What is clear is that fewer and smaller wobbles are good .
The only Technics 1200 tested is the one you supplied with MN bearing and Funk platter (presumably no record weight) and that measures remarkably well (its the plot you've been posting)?
And presumably the graphs show on paper what you hear on audition as the "warble"? The measured Technics deck shows a smooth(ish) circle which can be heard as low warble?
So, presumably, in the context of this thread, the next step would be to carry out the same test using the acrylic and strata platters, along with the technics original, MN ETP, and maybe MN copper, keep all other parameters constant (which means use a Mike New bearing to take the weight of the 10Kg platter) and see whether they have different shaped wobbles, and which one wobbles least? At the moment we don't know whether it is the inherent quality of the Technics motor which produces those plots regardless of the platter mass, or whether it is a "magic synergy" between the mass of the acrylic platter and the Technics motor?
Or, are we saying the graphs are pretty but irrelevant to warble? And we all just love Techies
That's agreed so far. I did use my Stillpoints record weight to produce that test reading.
No, I didn't measure a heavy platter so I know of no graph that shows the speed regulation problem with a Technics and heavy platter. All we are doing is speculating that it may show the issue.
Correct. I restate: we don't know what, if anything, we might see. However, some members have asked for objective measurement and I offered this as a way of seeing whether speed correction issues due to platter weight may be visible. It doesn't speak for platter material reflections or any other qualitative value of the platter.
Banned
Location: Granes - Haut Vallee de l'aude - EU
Posts: 2,830
I'm Richard.
Brilliant. Thanks Martin. I am pretty sure I've got that and it makes sense. I'll see if I can get AK measuring for when I go down to see him on Tuesday (pity I have to "waste" time on work first). Of course that will only be the 2 funks and the standard technics unless someone can lend him an MN (wait till I've confirmed he can set the tests up) I've also emailed him to have a look at this thread himself. If I'm not mistaken it brings up one of his favourite themes. (Does anyone have a dustbug I could borrow to take down with me?)
Also - unless I have again got muddled I am pretty sure this plot is for the premotec motor - with a belt drive - famously used in the Pink Triangle Anniversary, and although it appears and disappears without mention, I make it the roundest smoothest of the lot
This is probably sinful thread drift, but I'm just gonna have to take my chances with the naughty step, and indulge in wallowing in a warm glowing feeling of smugness. Arthur - get that bloody pimping project ready for tuesday. I trust you still have a premotec in a drawer to go with that old anni sub-chassis you found. I want to get a new thread started and I NEED MY TOYS!!!
Oh- soz - plot taken from PFM with thanks.
Posting Permissions
Reply With Quote
