Reversible Technics SL-1200MK2 Quartz Lock Hacking

Introduction

SL-1200MK2 has two different mechanisms for setting platter rotation speed: the "regular" oscilator (or what have they), adjustable by the pitch slider (and two variable resistors on the circuit board), and the venerable ultra-precise Quartz Lock engaged when the pitch control is at 0% and the green light is on. We're going to disable the quartz lock.

The purpose of this surgery is to solve the problem of two zero points on the pitch slider (more here). This problem exists in almost all 1200s I've ever seen, and even my virgin 1210s had their true zero points around the 1% mark when they came from the shop.

Disabling the quartz lock is quite simple. You will need no soldering or other special skills, just a steady hand to take the platter off and disconnect the wires. The process is reversible, so if you ever regret doing this and want your quartz lock back (or just want to sell your tables to an audiophile), you just need to connect what has been disconnected, and your turntables will be just like new, except the repressed memory of abuse they suffered, which never disappears completely.

I've done this to one of my turntables so far. I hope to take pictures and amend this page when I hack the other.

Caveats

This is for SL-1200MK2-A or SL-1210MK2-A. Other models of SL-1200 may be different.

If you break anything, I don't care.

You may be tempted to get a pitch slider for SL-1200MK3 or SL-1200M3D, but I heard their pinout is different (so it's unclear how to connect them to the MK2 turntable), and that they're not as responsive as the MK2 pitch control (so it's clear you don't want to, anyway).

I've only disabled the quartz lock, but I decided against removing the click, mainly because I'm not good with soldering iron. If you want to do that as well, read this article later.

Tools

You'll need:

• A Philips screwdriver of regular size.
• Small needle-nose pliers.
• A steady hand or two. If you don't have any, call a friend. Serious.

If you want to adjust the pitch controls (zero and pitch gain) later, you'll also need a small straight screwdriver.

The procedure (finally)

1. Take the plastic cover off completely if you haven't done this yet.
2. Take the cat off the platter.
3. Take the lame football-styled slipmat that you got for free with your turntable off the platter, dammit.
4. Turn the table off.
5. Disconnect it from the mains power.
6. Try to turn the turntable on to make sure you disconnected this one and not the other one. The red strobe light should not come up.
7. Take the cat off the platter.
8. Now take the platter off. Put your fingers into the two holes and just lift it, gently but firmly. Don't be afraid to pull, there's a magnet keeping the platter down.
9. Put the platter where it's unlikely to be be destroyed by forces of nature during the next ten minutes.
10. The plastic cover underneath the platter has five screws near its edges. Unscrew them.
11. Take the plastic cover off.
12. On the right side of the circuit board there's a white(?) plastic connector with four wires: brown, red, orange and yellow, in that order from top to bottom, with a space between brown and red. (If anything is not as described, my advise is to put it all back together and go see someone competent.) This is your pitch control connector. Disconnect it. Now you have the female plastic connector in your hand and five metal prongs on the circuit board.
13. The wires end with small metal "tubes" which go inside the plastic connector. Each "tube" has a small bump near the end which keeps it in. You may see them if you look at the connector from above. Our goals is to take the wires out. See the plastic thing that holds the bump, thereby keeping the wire "tube" inside? Lift it gently with the pliers and pull the wire out. (If you ever decide to re-enable the quartz lock, just push those wires back inside the connector.)
14. I don't know which wires you destroyed right now, but you should have disconnected the orange wire to kill the quartz lock. If you want to disable the green LED as well, pull the yellow wire out.
15. Connect the connector back.
16. Isolate the loose wire ends with small pieces of insulating tape, and tape them somewhere they won't touch anything.
17. Now is good time to adjust the pitch, so the platter will rotate at the set speed when the pitch slider is around zero.
    1. Notice the variable resistor on the circuit board, just by the word PITCH above the pitch slider connector.
    2. Put the platter back on. Just like that, without the plastic cover.
    3. Turn the platter until you see the resistor through one of the holes.
    4. Connect the turntable to the power, turn it on, set the pitch slider to zero, take the cat off the platter, press START and watch the dots on the side of the platter under the strobe light. If the big dots move, STOP the motor and adjust the resistor slightly with a small screwdriver through the hole in the platter. Repeat this START-look-STOP-adjust routine until the dots stop moving or until you stop caring.
    5. Turn the turntable off and disconnect it from the mains power.
    6. Turn it on, see it still off.
    7. Take the cat off the platter.
    8. Take the platter off.
18. Put the plastic cover back on the circuit board and screw it in.
19. Put the platter back on.
20. Put the idiotic looking slip mat on, connect the turntable to the mains, turn it on, put the record on the platter, the needle on the record, press START and enjoy the mixes. And try to keep the damn cat off the turntables.

Epilogue

And they have lived happily ever after, gathering around the mixer at nights, shining their styli illuminati at each other and remembering the times when a human would not necessarily put a screwdriver through you during your first night together...

If you have any questions or corrections, please don't hesitate to mail me. I'll be glad to help; the only limit is my competence.