Fixing the "Two 0's" problem on Technics Pitch Control?

[deejv]

Hey guys, havn't posted in awhile, but i really need some help this time. Apparently my 1200 MK2's have two 0's on the pitch. Now i know i havn't been mixing like this for ever, or else i would have noticed. But it seems like just the last weeks that this started to happend. Have any of you heard of this?
Well i did some research and found that there was a solution to this. But that solution would require me to open up my table. The problem is, i REALLY don't want to mess up my table. So if i choose to do this. I'm going to go in 100% precautious, and i want to know ANYTHING that you guys reccomend me to notice or watch out for. I mean, i deffinetly would rather be safe than sorry in this scenerio.

Ok, so one of the soltuions read like this:
"Contrary to (popular?) belief there is no way to lose true 0% pitch when the slider is in the middle - no matter how you hack it. When in the middle there is a switch which is thrown which bypasses the pitch slider and the motor is now crystal locked at the exact speed. But, if your deck is messed up in this area when you move the slider in the + direction, for example, it will slow down at first and will then move to 0 and then will speed up as you move it more in the + direction! In other words you now have 0 at two places. So this is for reference if you need to get your pitch slider so that 0 is really in the center. Open up the base, look where the pitch pot is. There will be a hole about 3-5mm in diameter where you can see a small pot on the other side. Hook up a multimeter to that pot (again, connect to the center lead and the one nearest the edge of the board I think) and use a small adjustment screwdriver to adjust it to 2.7kOhm."
Any comments on whether i should do this or not? Excuse my lack on knowledge, but what exactly is a multimeter?

Another solution read like this:
"Zeroing your tables........
This will go in a series of steps:

1. Be sure you are completely sober. (this is not a joke)
2. Unplug the tt from the wall and the mixer/amp/whatever.
3. Lock the tone-arm in place and secure any fly-arounds.
4. Place the dust cover on the table and put a pillow on the kitchen table.
5. Place the table upside down on the pillow.
6. See all of those screws on the bottom? Take 'em all out except the ones around the little round piece of metal holding in the signal cables.
7. I bet you've found all of the little washers. Don't LOOSE them. There also little chrome spacers in the corners and where the long screws go in. SAVE these too.
8. Carefully pull off the rubber housing taking care not to damage the power cord while getting excited.
Do you see the circuit board with the pitch slider on it, there should be a hole in it with a screwdriver slot in it, this is your zero adjust, if you do not see a hole, some don't have 'em, then you'll have to remove circuit board, follow directions below.
Reach around and pull the knob off of the pitch slider on the top.
Unscrew the screws holding down the board and pull straight up. Now you should have a circuit board in your hands, with; a large slider, a LED, a resistor, and a potentiometer-this is your zero adjust.
10. Clean out the potentiometer by blowing on it or spraying TV Tuner and Contact cleaner on it, many times dust causes these problems and can be remedied by a cleaning.
11. Place the rubber housing on the table and temporarily flip it over, plug it in and check your zero again, if all is well you are done and can put your baby back together and continue to 12. Matching Your Tables, if not, then continue.
Unfortunately you have to adjust your potentiometer . Now bear with me. If your zero point is too far forward then the potentiometer must be moved clockwise if you are doing it from the bottom and counterclockwise if turning from the top, TOP BEING THE SLIDER SIDE.
13. Turn the potentiometer in small increments each time, checking the position by repeating step 11.
14. Within minutes you should find the zero point you are happy with; just don't get in a hurry, you only want to do this once.
15. If you are happy with the zero point, then put the tt back together and have a non-alcoholic drink, because you might have to continue. "

Any comments on whether or not i should attempt this method?

Well, i definetly would want to try one of these methods. So if you guys have ANY feedback, knowledge, or opinions on this subject at all. I would really appreciate it.

 

[mountainboy]

first off i only read the top portion of your post - i apologize beforehand...

it is pretty straight forward to remove the zero point - 2ways, either remove the quartz lock by removing the little ball bearing in the pitch slider (a bit more complicated) or by simply adjusting the zero point to match the quartz lock position...

before adjusting the pot, take a pencil and gently mark the location of where it is at right now... then move it slightly, plug the table in, put the platter on, and see how close to zero you get... then repeat, making sure to unplug the deck before doing anything... and making sure that the platter is on before turning it on...

it takes time but it's worth it.

 

[dynagroove]

deejv - if you are just messing with the pitch control, there is very little you could damage while you are inside your deck as long as you stick to that area. if you remove the ball and hence the click, you are not getting rid of the quartz lock, just the click. all the click does is hold the pitch control in place over the contacts that engage the electronic quartz lock. a while ago, i decided there was no reason i actually need the quartz lock. i personally don't care if a record is spinning at exactly 33.3 or 45 rpm. but i do care if i have 2 zero points. so you may want to do what i've done to every 1200 i've modded. everyone i've done it for has really liked the results. it will require a little soldering, but is completely reversible if you don't like it. basically, you remove the quartz lock wire from the pitch board and isolate it, then remove the click from the pitch control and calibrate the pitch with the control adjuster and control gain pots. no click, only one zero point guaranteed. i'm happy to give you specifics here or i can PM you. - jeff h

 

[ki_cz]

I might be interested if it is really easily reversible and there is little chance of screwing up. Does the LED still light up even though the click is removed?

 

[dynagroove]

i'll post specifics tomorrow. you do have to know how to solder which is slightly more difficult than "knowing how to glue" - jeff h

 

[deejv]

Hey guys, well turns out fixing the 2 0's was easier than i thought. After opening the decks, and seeing the pitch, i found it pretty easy to fix (although it took me a minute to find the potentiometer).

Dyna- I would be interested in your mod. Id also really appreciate those specifics. I might consider doing it.

this may sound stupid, but what exacly his soldering?

Also, now that i'm at it. I was interested in caliberating my decks. I've ran a search on this board, and got some real useful info. Now all i need to know is:
1. Exactly which strobe dots are the "6%" dots?
2. Exactly why do we set it to 6?

So if i do this mod, i won't have to go into my fader and fix that again do i?

 

[dynagroove]

ki_cz - yes the LED still lights up even though there is no quartz lock. the quartz lock contacts are still being closed which is why the LED still lights up, the quartz lock has just been removed from the circuit.

deejv - here is what jeeves has to say

solder - an alloy (usually of lead and tin) used when melted to join two metal surfaces.

you need a soldering iron, solder and a solder wick to remove solder.

here is the quick and dirty on what to do. get the top cover below the platter and the bottom cover off the turntable. if you need specifics on how to do this, i can post links, or do a search. there is a ton of info on how to take apart your 12's out there. from the top, disconnect your pitch control - it's the connector on the far right of the main circuit board. from the bottom, remove the 2 screws that hold the pitch control down, pull the tape that holds the wires to the chassis (look in the opening to the top side) and pull the entire assembly away. now if you just want to remove the quartz lock, desolder the orange wire from the pitch board and either shrink wrap the end in wire insulation or use electrical tape (which i prefer not to use). that's it - no possibility of ever having 2 zero points. it also makes calibration of the pitch very easy as i discussed in an earlier post. now if you want to remove the click while you are in there, it's a bit more involved. first desolder the pitch LED from the board and pull it out. then remove the 2 screws that hold the top plate on and pull that plate off. next you can either do one of 2 things. desolder the 8 connections on the back of the pitch board, untwist the 4 of them that help hold the fader in place, pull the fader free and then pull back the 10 tabs that hold the cover on the fader. or you can very carefully pry the 10 tabs back from below the fader with it still on the pitch board. you may only have to pry off 5 tabs on one side if you can angle the cover carefully off. keep the fader control pulled up against while you remove the cover. carefully push the fader control down through the cover. the bearing will pop out and you will have to pull the spring out. be careful not to touch the fingers of the contacts with any of the tabs as you can easily bend them rendering your pitch control useless. pull the control back into the cover. if you need to, clean the fader and carefully clean the contacts and reassemble the cover to the fader board. lock down the tabs and resolder the fader board back into the pitch board if you removed it. mount the cover back on and solder the LED back in place. put everything back together and make sure the orange wire is not being clamped down by anything (as it can make you miserable trying to figure out what you did wrong). let me know if you need any more specifics. - jeff h

 

[deejv]

wow, thanks man. i really appreaciate it. i'll probably copy and paste it on word and save it. i'm not sure if i have enought guts to do that right now, but i'm so tempted. i mean, i don't really have any soldering skills, and probably have to ask somebody before ruin'n the decks.

well, if you can. can u help me on the other questions?

Also, now that i'm at it. I was interested in caliberating my decks. I've ran a search on this board, and got some real useful info. Now all i need to know is:
1. Exactly which strobe dots are the "6%" dots?
2. Exactly why do we set it to 6?

So if i do this mod, i won't have to go into my fader and fix that again do i?

 

[dynagroove]

1. Exactly which strobe dots are the "6%" dots?
2. Exactly why do we set it to 6?

So if i do this mod, i won't have to go into my fader and fix that again do i?

the top row of dots is the +6% marker. i think i read the +6% then set 0% at 0% method somewhere on the net many years ago (1200 faq maybe?). after trying different methods and not wanting to shell out a grand for an ocilloscope, i settled on this method. it has worked well for me. if you do the quartz lock removal mod and don't touch the pitch adjustment pots, everything should be just as it was before you opened it. either way it shouldn't be a big deal since your deck will be open to do the work anyway. i always check the calibration before i put everything back together - i hate having to open a deck up twice. - jeff h