Technics SP-10 Gallery
Technics SP-10, mkII and mkIII
user 510's sp-10 mkII (USA)
Ken McCarty's sp-10 mkIII (USA)
data, articles, notes and links:
links:
http://www.vinylengine.com/library/technics/sp10.shtml
Articles & brochures:
Thanks to Ken Mccarty for the above article scans.
Notes:
Notes on the speed regulation:
Thanks to The Vinyl Engine, we have access to good copies of the service manual
to assist (heavily) in this project. I'll try to paraphrase and condense the
explanation of the various circuits that regulate platter speed on this
interesting little record player.
1) First there is quartz oscillator that generates a reference signal. The
reference signal is split by a frequency divider into the appropriate frequency
for each of the three available speeds. And this speed information is stored in
digital memory.
2) There is a strobe logic circuit that is used to flash the neon strobe bulb.
3) Frequency Generator.
It says that the Frequency Generator is integrated with the platter drive motor
and converts platter rotation speed into a frequency. And the output of this
frequency is fed to the speed and phase control circuits.
4) Phase Control Circuit
The phase control circuit detects phase difference between a reference signal
(see item #1) and the frequency generator signal (item #3) and generates a
control voltage. So between the reference signal, the frequency generator and
the phase control circuit the rotation of the platter is "locked" to
the reference signal.
5) Speed Control Circuit
Here it describes a "sample hold" circuit that converts output of the
frequency generator into an electrical voltage. This is the control voltage
which maintains platter rotation speed.
(Btw, we already knew that the motor was brushless DC, right?! DC motors are
speed-controlled by voltage. More volts = more rpms....more or less.)
6) Drive Circuit
Here I just quote the service manual.
"Two control signals are composed and applied to the drive circuit to
maintain a forward motor rotation. The drive circuit supplies full wave drive
current doubling current efficiency. It supplies drive current in both
directions for a symmetrical rotation in either a forward or reverse
direction."
7) Start/stop Circuit
Hit the on button and the circuit starts the platter rotation. hit it
again and a reverse drive plus mechanical brake is applied.
8) Mechanical Brake Actuating Circuit.
Here it describes a circuit that operates a solenoid that pushes a brake shoe
against the platter. And this is working together with the above noted
start/stop circuit. There's more but you get the idea.
There you go. Tech-geek translated into English courtesy of The Analog Dept.
Pretty advanced stuff for the mid nineteen seventies. And I presume that all of
this circuitry is really the heart and soul of this little player. (assuming
that it does have soul) It makes sense then to insure that all circuits are
filled with happy little electrons busily going about their business. No sick,
tired or injured electrons allowed!
For me, giving maintenance to these circuits will be the hard part. The
mechanical parts shouldn't be as much of a challenge. Get past the circuitry,
and its just a platter that spins on its bearing.