ACP-100

THE FIRST TURNTABLE


Ok, today just arrived my first SL-Q2. It is definetly the right choice for this project.
Solid aluminium case, no unneccessary switches and a nice look.
It has a Ortophon E System with it which is a very sophisticated system that will suit my needs for sure
(yes, sometimes even I want to listen to a real vinyl record ... at least to verify my computed data bulk)
Here are the last pics when it was still one part...


Here are some close-up's from the system


Well, after beeing impressed from the outside I started to take it apart and what I found in there
impressed me even more. (see pictures on the "Going into detail"-section)
The guys from Technics really didn't bother about building up a mechanism with
literally hundreds of parts instead of putting one or two servo motors in it. But it works, and it is
funny so watch it doing this.
Also remarkable is, that the board for the sound input and output has overall dimensions of 5cm x 2 cm, whereas
the motor drive and control unit is about 20cm x 13cm! But this seems to be an advantge of turntables in general.
It was an interesting to see these (in our days rare) handcrafted boards where the layout is not done by an
autorouter but by a (more or less) skilled worker with (definetly) much patience. Anyhow, tracking the wires on it sometimes is a mess.
Unfortunately I only have the Operation Manual for the SL-Q2 and I am missing the Service Manual with all
the shematics and block diagrams in it. Somehow, it is not available in the net (or, to be precise, only from
reprinters who sell and try to get rich). So, at this time I am dealing with the Technics SL-1210 Service Manual but
the schematic is quite different. Maybe I will have to invest the money and buy the Q2-Service Manual.
Being impatient, I started to take up the schematic manually for the most important parts and compared it to
the SL-1210s. As the SL-Q2 chipset contains the AN6675 (Motor Driver, IC101) and the AN6680 (Speed Control, IC201)
there ist only the AN6682 (Pitch Controller, IC301) and the TC4011BP (Pitch Selecter, IC302) missing to make
it a real SL-1210 electrically.
The TC4011BP is a quad NAND-gate and is available at every radioshack for less than 1.
The AN6682 is not available in normal quantities, but many vintage radio shacks sell them for about 10, which
is acceptable. In my eyes the AN6682 is kind of a phase-locked-loop-vdo which was not available in the 70s and
therefore put together by Technics for their own purposes. It might be substituted with a 74HC4046 which is
available for a tenth of the costs.
The AN6675 and AN6680 are hard to get and expensive - fortunatley we have them already in the SL-Q2.
They are still produced by Panasonic because they are also built into the new SL-1210 turntables and even in
the spanking new SL-DZ1200. It is also remarkable that Panasonic seemingly never updated the board-layout for
the 1210, so when you buy a brand new one, you'll get that old-school layed out board.

Well, after studying the board for a day (see the "Goint into detail"-section),
I came to the following conclusion:

A 100mm pitchfader will be installed on the right side and a board will be constructed to rebuild a 1:1 SL-1210
pitchfader-control unit. Attaching this board to pin 2 (FI) of the AN6680 will give you a full featured pitchfader
in professional quality. The 1210-like reset-switch will not be implemented (at this time).
The pitchrange should be extended to feature more than +/-8% if possible.

A switch will be installed to deactivate the auto-startup/auto-stop function and the stop button. In exchange, the stop button will be attached to
a toggling-circuit which makes it a start/stop button.

The motor then runs independent from the tonearm.
Motor starts, when start/stop is pushed once, independent from the tonearm position.
Motor stops when start/stop is pushed again, independent from the tonearm position.

Simply by switching, you will change between the original behavior of the SL-Q2 and a (almost) manual operation.

Unfortunately, it is not possible to deactivate the auto-return function (when the tonearm reaches the end
of the disc) electronically. Auto-Return is realised mechanically in the Q2, and I don't want to remove parts
in the mechanic. If you don't bother, it is no big thing (see "Going into details").


BACK