GAE and MK4 AT-150MLX, bone stock arms. MK3 was EPA-B500 base with EPA-A505 arm and an EPC-P100CMK4 cartridge.
IIRC KD-550 motor is Matsushita OEM. Not PLL either, so that may be a close call. Certainly be interesting to find out.
JP: I never cease to be amazed by your toy collection 🙂 . Don't suppose you have any sweep records that go to 40KHz? would love to see how that EPC performs at HF and would make a great data point for the discussions on effective tip mass we've been having.
How's the DP-100 restore going?
The KD-550 IS PLL just not quartz locked. But controllers can be modified 🙂
How's the DP-100 restore going?
The KD-550 IS PLL just not quartz locked. But controllers can be modified 🙂
Last edited:
Thanks, @LD. As both revolutions track most likely a bearing issue? Do you have a plot for a healthy MK4?
@Hiten - serviced and using my replacement module for the MN6042. This one does have an issue: something in the drive circuit is temperature sensitive so calibration drifts until it's warmed up. I'll try to record a sample from one of my completely healthy units.
@Hiten - serviced and using my replacement module for the MN6042. This one does have an issue: something in the drive circuit is temperature sensitive so calibration drifts until it's warmed up. I'll try to record a sample from one of my completely healthy units.
Direct drives are bound to have both good and poor examples. There is no way the magnets can be exactly matched in production.
The unit from post #337 is remarkable
The unit from post #337 is remarkable
Sorry, missed this.
The DP-100 is back together. I fabricated some caps for the suspension. Haven't tuned it up or ran it - took a full time job so free time is minimal.
I've some 40-50K sweeps. Need to find them.
I think one might tell a bearing issue from free rotation spin down time..... I have one SL-1200 MkII plot that shows a similar trait, but several others that don't.
Balance or levelling, perhaps........? In general, SL-1200's are exemplary IME, at least in terms of rotational stability.
LD
Hiten: your Q3 is the same 'green motor' as the 1200 MK4 albeit at 12v instead of 24v so no reason why you shouldn't be able to get rotational stability very close.
Thanks Bill. That is good to know. A little comfort to know that this mid range TT is good. I like the auto operations too.
Earlier I only used to listen to rumble noise by stethoscope. After this thread I will try to listen any pitch variations. Sustained sounds of music pieces will be good start I think. Other way is to measure current drawn by the motor by precise multimeter or some other way I suppose. Am not electronically savvy😱
Regards.
Earlier I only used to listen to rumble noise by stethoscope. After this thread I will try to listen any pitch variations. Sustained sounds of music pieces will be good start I think. Other way is to measure current drawn by the motor by precise multimeter or some other way I suppose. Am not electronically savvy😱
Regards.
...if I remember there was an Australian guy who used to sell bearing upgrades for sl-1200 which reduced the noise considerably. I think bearings/lubricant also affects speed stability.
A number of people have done upgraded bearings. Not sure if Dave Cawley still does his version. He and the australian didn't get on well on other forums (fora?).
When mid price DDs were cheap I collected some motors to compare, which will still happen these days as seeing the work Calvin did on building a TT with a green motor I thought it would be fun. One day.
What does intrigue me is that the first plots I saw of an SL-1200 showed considerable cogging which these don't I need to see if they are still up on pinkfish and lencoheaven.
When mid price DDs were cheap I collected some motors to compare, which will still happen these days as seeing the work Calvin did on building a TT with a green motor I thought it would be fun. One day.
What does intrigue me is that the first plots I saw of an SL-1200 showed considerable cogging which these don't I need to see if they are still up on pinkfish and lencoheaven.
This is what I got with the direct Hilbert transform method and simple two pole filtering at 100Hz. LD, I just grabbed 1.8 sec out of the middle of the file do your plots represent more than one rev? This is the MK4_XG-7001_WF_1 file recently posted. I used the library I wrote for LA which is a free download at Jan's site. Again one nice feature is that Python does not care about power of 2 FFT's.
I need to finesse the cartesian to polar transform to make the polar plot look right. The default really wants the origin to be 0 so visually there is no resolution around 3kHz. I used SoX to convert the .wav to generic text data.
I need to finesse the cartesian to polar transform to make the polar plot look right. The default really wants the origin to be 0 so visually there is no resolution around 3kHz. I used SoX to convert the .wav to generic text data.
Attachments
Last edited:
There were two 1210s on PFM, both showed cogging and the second one had an eccentric polar as well.
The eccentric polar is either a bent spindle or an off centre record. There is no easy way for healthy motor to cause it.
Regular cogging could be due to incorrect current drive waveform or maybe a motor gap error. There is a lot of scope with a DD motor of fine tuning the commutation to reduce cogging
Sadly the original files are no longer on PFM and the original recordings I don't think were published. Shame people use hosting for these things rather than uploading, but hey ho.
I think that there is a lot on tuning we can learn from this. As well as finding out that SP-10 owners were (damnit) right all along 🙂
I think that there is a lot on tuning we can learn from this. As well as finding out that SP-10 owners were (damnit) right all along 🙂