Minidisc deck repair tips
This page contains a variety of notes I made while effecting repairs to my
Sony MDS-S30 minidisc deck. Much of this information will be useful in
relation to the MDS-S35 and MDS-S37 models as well, due to their similarity
to the MDS-S30. In addition, the MDS-302 and MDS-303 are apparently similar
or the same as the MDS-S30 and MDS-S35 respectively, so these notes may be
helpful to owners of these models as well.
I am hoping to include some sketches on this page to help illustrate a
number of points. This will happen "as time allows".
Before attempting any repairs, please refer to the
Final thoughts at the end of this
Inconsistant operation of unit / unit dead
The power supply in the 'S30 deck contains a number of very heavy
components. The bulkiest (the transformer) is secured to the chassis with
dedicated screws, although even here there is a possibility of finding dry
joints on some transformer pins. In addition to the transformer, there are
some very large electrolytic capacitors on the board - their connections to
the PCB are well worth checking.
Failure to spin a disc
Symptoms: The unit powers up as expected. A disc can be inserted and
is correctly accepted by the unit, but the disc is never spun. A motor
can be heard to be starting but no movement is evident anywhere.
Possible cause: When a disc is inserted, the sled (the assembly which
drives the optical and overwrite head across the disc) is instructed to
return to its innermost position. A microswitch is used to confirm when
the sled reaches this position. A dry joint on one of the contacts of
this microswitch, or a broken switch, will prevent the system receiving
this signal. The sled motor therefore remains energised indefinitely
while the unit waits for a confirmation which will never arrive.
Repair notes: It is possible to access this switch without
dismantling the drive mechanism. Remove the drive from the minidisc
assembly and move the sled to the outer-most position (this can be done
by rotating the large gear on the top of the assembly gently by hand).
With a steady hand, it is then possible to assess all solder points of
the offending switch; care must be taken to ensure that the iron does not
touch any of the nearby plastic transport components.
Failure to record
Symptoms: The unit plays back discs with no problems and when
attempting a recording everything appears to function correctly. When
this recording is played back, the disc is spun up and the head can be
observed to be seeking as expected. No audio is produced and for about
10 seconds the track time displays "00:00". After this time "00:01" is
shown which remains for a very long time. After ejecting a disc you have
attempted to record on, the disc will be registered as "blank".
Attempting a "continuous write" operation in "service mode" also appears
to work, but a "continuous playback" reveals that no data has been
This fault is apparently rather common in MDS-S30, MDS-S35, MDS-S37,
MDS-302 and MDS-303 models, according to the
User reported problems
The minidisc community.
Possible cause: It seems the spring material used in the overwrite
head in these models can get weak after several years. This results
in the head not firmly resting on the upper disc surface during
recording; the magnetic information is therefore not transfered to the
disc and no information is written. However, because the laser is
correctly switched to "write" power, the disc's magneto-optical layer is
brought to its curie temperature. With no magnetic information being
supplied, the disc sectors are effectively erased. On disc ejection this
basically wipes the disc's table of contents, giving a "blank disk".
Repair notes: Record functionality can be restored by the replacement
of the overwrite head. The original part has been superceded by a new
one, and my impression of the new part is that it might prove more
reliable than the original. The Sony part number for the 'S30's new part
is 1-500-304-21. It is described in the parts database as an "overlight
head" (sic), presumably due to a typo. In fact, the full description of
the part is "Overlight head, MDS-S35", so it seems that at least the
MDS-S35 shares exactly the same overwrite head as does the 'S30.
It is worth noting that the new head assembly is slightly longer than the
original. In my deck this meant that when a record operation was
commenced, the forward edge of the overwrite head got caught on some
black painted metalwork associated with the disk loading mechanism. This
was easily solved by trimming the metalwork with a nibbing cutter to give
sufficient clearance for the head across its entire travel.
- I have been unable to track down a service manual or schematic for
the MDS-S30 or any of it's close relatives. Although substantially
different (with a different ATRAC version for a start), I have found
the MDS-JE510 manual to be helpful. Although the board layout and IC
pinouts are completely different, the circuit at the base level is
remarkably similar. The JE510's manual is also helpful at identifying
the various testpoint abbreviations used on the PCB silkscreens, which
haven't changed between these two models. In addition, the description
of signals used by ICs in the JE510 (together with a knowledge of which
signals the test points refer to which can also be gleaned from the
JE510 service manual) allow a reasonably detailed picture of the 'S30's
operation to be deduced with relative ease.
- When removing the front panel of the 'S30, there is a thin copper tab
which connects the ground plane of the display board the metal chassis
of the unit. This tab has a hole in it and is designed to be secured
by one of the screws which hold the front panel on. Its correct
seating is between some plastic from the front panel and the chassis
itself, and it is located on the left side of the front panel when
viewd from the front. When removing the front panel, make special note
of the arrangement of this tab and ensure its correct replacement when
the panel is refitted.
- The minidisc assembly contains the solenoid which activates the cover
flap on the front panel which covers the hole into which a disc is
inserted. The two are connected via a `hooked lever' arrangement which
easily disengages when either the front panel or the disc mechanism are
removed. Ensure that the lever is re-engaged correctly when
- Take special care when removing and replacing the screws which hold the
minidisc drive mechanism onto the larger minidisc assembly. These
screw directly into molded plastic, and the threads could be stripped
if care is not taken, especially if many disassembly/reassembly cycles
are required during testing.
- When removing the minidisc drive mechanism from the assembly, take care to
avoid damage to the overwrite head. The best way I found to effect the
removal was to pull the rear of the mechanism up first, which allowed
the rest of the drive to be manipulated clear of the assembly.
Replacement is the reverse.
If anyone has anything further to add to this collection of tips, please
let me know. In
particular I would really like to obtain a copy of the service manual for
the MDS-S30, or even just a schematic diagram.
Note that this information is being provided as a service to the minidisc
users of the world. It has come from personal `trial and error' experiences.
Please do not attempt repairs of minidisc equipment unless you are qualified
or have a technical/electronic background. Decks such as the MDS-S30 are
mains operated and therefore have mains voltages present within the case
when in operation.
The information on this page is supplied without warrantee and with no
guarantee. The author will accept no responsibility for injury, death or
damages which result from the use (improper or otherwise) of this
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