- Denon DMD-M10 minidisk recorder - 2 Updates
- DMM - 4 Updates
| dplatt@coop.radagast.org (Dave Platt): Apr 23 12:21PM -0700 In article <39r38gdhf1kr84cetqq9p9e8a5fclrnd74@4ax.com>, >However minidisk uses magnetic recording and playback similar >to a floppy disk. The laser is only used when recording to heat >the disk and thus allow it to be altered by the magnetic write head. All of the information I've found on Minidisc, says that it works the other way around. During recording, the laser operates at high power, heating up the magneto-optic layer on the disc above its Curie point. The fluctuating magnetic field from the write head is "captured" by the MO layer as it cools back below the Curie point. During playback, the laser is used (at low power) to sense the magnetic orientation of the MO layer by sensing changes in the polarization of the reflected laser beam (via the Faraday effect). When playing pre-recorded discs (made more like CDs) the laser is sensing reflectivity differences rather than polarization. References: https://www.minidisc.org/minidisc_faq.html (item 9) as well as The Great Font Of Dubious Knowledge (a.k.a. Wikipedia). For more detail, you can take a look at the original Minidisc patent: http://www.minidisc.org/patents/pdfs/US05244705.pdf - the basic descriptions of the recording and playback processes are at the bottom of column 9 and the first part of column 9, on pages 15 and 16. The technical advantage of this dual approach is that the magnetic head doesn't have to "fly" at an extremely low height over the surface of the disc. In a hard drive, the gap between head and media is truly tiny... much smaller than the diameter of a human hair, and often smaller than a particle of tobacco smoke. It has to be this close, in order to be able to read and write very-tiny bits. That would be very hard to pull off successfuly for a removable medium like MD. With MD, the write head can be larger, and further away from the surface. It produces a fairly broad area of magnetic field, but this affects the material only in the tiny area being heated by the laser (and cooling down immediately thereafter). |
| Lucifer <LuciferMorningstar@bigpond.com>: Apr 24 11:22AM +1000 On Fri, 23 Apr 2021 12:21:11 -0700, dplatt@coop.radagast.org (Dave Platt) wrote: >surface. It produces a fairly broad area of magnetic field, but this >affects the material only in the tiny area being heated by the laser >(and cooling down immediately thereafter). Thank you so much for that. I had the wrong idea of operation. However, looking at my minidisk recorder playing the magnetic is actually touching the disk and the head moves across the disk when I select a different track. Now I know how minidisk works I can take a different approach to fixing mine. Thank you again. |
| "ohg...@gmail.com" <ohger1s@gmail.com>: Apr 23 11:04AM -0700 On Friday, April 23, 2021 at 11:47:47 AM UTC-4, Peter W. wrote: > Don't get me started on Harbor Freight.... > Peter Wieck > Melrose Park, PA *resisting* *temptation* *of* *getting* *Peter* *started* *on* *Harbor* *Freight* .... |
| Cydrome Leader <presence@MUNGEpanix.com>: Apr 23 07:31PM > Hi Group, any recommendations for a good DMM, preferably a Fluke. under a $100.. are the ones made in China reliable.??? what kind do you use.??? What is the end use? |
| John Robertson <spam@flippers.com>: Apr 23 12:41PM -0700 >> Peter Wieck >> Melrose Park, PA > *resisting* *temptation* *of* *getting* *Peter* *started* *on* *Harbor* *Freight* .... "resistance is futile" ('42' and all that) John ;-#)# |
| Phil Allison <pallison49@gmail.com>: Apr 23 05:07PM -0700 Ralph Mowery wrote: ================= > I have a Fluke t100 that is made as an electricians test meter. I have > put it across some 240 volt circuits while set on ohms and no effect to > the meter. ** That is not unusual, it is easy to protect the ohms ranges of a DMM from voltages up to 240VAC. Along with being ( almost) drop proof, it is one of the great benefits of DMMs compared with analogue types. The main safety features of a good multimeter are that the 4mm plugs are self shrounding and the battery compartment needs a tool to access. Goes a long at toward preventing accidental contact with dangerous voltages. Meters with unfused *high current* ranges are a hazard around car batteries and the like, as the leads can smoke, burn or even explode. Not likely at all with mains power as gross overload trips breakers *instantly*. .... Phil |
| You received this digest because you're subscribed to updates for this group. You can change your settings on the group membership page. To unsubscribe from this group and stop receiving emails from it send an email to sci.electronics.repair+unsubscribe@googlegroups.com. |
No Response to "Digest for sci.electronics.repair@googlegroups.com - 6 updates in 2 topics"
Post a Comment