Lucky it wasn't worse...

hi! sorry that i didnt answer in a while, but i had a thing (exams actually)

well the reading is 4,86V. is that still in range?

for one i'm pretty sure that the error is definitely not caused by the pitch control unit, i switched it to my other deck and that one still works fine, plus the last time the faulty deck was behaving strange i plugged out the cable leading to the pitch and it would still speed up and down randomly in the same manner (the usual thing what happens if you pull out the cable is that it speeds up and down very symmetrically)

also, when touching the platter i could feel a force that is pushing it forward or backward

and the strobe light starts flickering whenever I touch the platter and move it forwards or backwards by hand, which is weird (this happens all the time when the deck behaves strange but it happens also when it runs fine but i move the platter by hand)

when replacing the diodes i would have to remove the circuit board they're on and stick on the new diodes and solder them on the back of the board, right?? can u remove the board easily?

well another thing is, when i was putting the pitch control back in I decided to make it a bit smoother and put in some grease and it didnt get any better so I tried other things but none worked, i realized that the not smoothness came from the electrical contacts producing friction (and not the upper part of the slider where i had put in the grease) since they were pushed pretty much together so i did some other things which led to the contacts being farther apart from each other so it went smoother, the downside is that now every time i push the slider in a certain way the contacts won't touch at all thus making the pitch go crazy

is there something you could put on the contact slider to make it go smoother??

Go easy on me if I get a bit all over the place, I just got home from working untill 5am (shooting a short film set at night).

If the reading on the didode is 4.8 V it may be that the transistor 2sd637 is ok (and the diode tho it should read 5.1 or 5? not really sure what sort of tolerance it should have), I have a feeling that when I blew my transistor, it casued a fault with the diode - ie the problem was related. By the sound of it, you problem is different to mine anyway, as my strobe would filcker when ever I set the patter in motion, and not randomly, and not by touching it with my finger. It is a strange issue indeed. It seems more like something may be lose as opposed to being broken, but with electronics, who knows.
One thin you can try is to remove the IC's (compter chips) from the good board, and swap them with the dodgy board and see if one of them is faulty. It's not har, but it is a process of elimination. I was actually told to try this to solve my problem by a tech, but it didn't help me, and that's when I looked into other things. There are 3 to try and swap, and using the blue cap as a starting point:

IC 301- Top right,
IC 302 - next to it
IC 201 - bottom right - the one with Technics printed on it.
If it proves to be one of those, you can order them on the net, or from a dealer - I'll get part numbers later if needed.

In answer to how to work on the board, disconnect the mains, unplug the three wire looms that are around the edge, then there are just tree screws to take out, and cut the zip ties and you can lift the boar partly out. It will still be connceted to the power board,so I just fold it over and work on it that way. I don't have the tools to dis assemble the wire wrap attached to the posts from the power supply board. Then, using a solder sucker and soldering iron, desolder the chips (only do one then swap it over and try it - it really would help if you can recreate the problem with intent). if you can solve the issue with this method, then you just need to replace the chip with a new one.

This is really the only other option I can give with my knowledge. if that doesn't work, you may need to send the board away for repair - google the turtable factory - I think that's their name. I've seen lots of posts elsewhere saying to send stuff to them. It would mean disconnecting those wire warps I spoke of, but it saves freight cost on the whole deck.

Part II
Pitch fader

read this first

http://www.tranceaddict.com/forums/...scratchy+faders

I'm going to bed for now, but I'll answer any questions you might have after you read that thread

first of all thanks again for your reply but man that is going to be a huge operation

i'm really scared to replace the parts with my good deck since unlike the broken one, where it doesn't matter if I try to fix it myself and brake something accidentally, I could in the worst case end up with no deck at all

i'm definitely gonna have to think this through..

regarding the fader, i read the thread but it really doesn't apply to my case, it's something really specific to the technics 1200 mk2 pitch fader.

the question would be which places you'd have to lube in order to make it run smoothly or in a more general way, what are the factors that can make it have bumps (positions where it offers more resistance than in other places)

when I opened it up I noticed that it hat some sort of rubber inlay that would fill the gap where the slider is in, and in some places that inlay was narrower than others so I tried to make it wider - next i thought it would be the outer walls which where somehow bent in in places so i tried to make them even and of course I put grease everywhere but the actual contacts.

when i put it all back together and tried it out it still wasn't very smooth and i looked at it from the side and it looked like the contacts of the slider where pushed really hard to the contact board, thus creating a lot of friction between the two. what I stupidly did then was to change the slider (removing part of the upper structure) so that the contacts would be further apart, but now they are so loose that they don't make any contact at all sometimes.

what I think now is that maybe the rubber inlays do offer a certain resistance which is higher than the friction produced by the contacts which is why you have to apply more force to move the slider to begin with but it still is continuous, and in widening the rubber inlays I killed that bigger resistance which is why the friction between the contacts is now more noticeable. (does that even make sense??)

aw well at least i have one good deck left

Sounds like you already attempted to pull the fader appart (ie strip it into it's seperate pices) Is that right? When I pulled my fader appart, there was very little lube in there, more like a tiny amount of oil which had become clogged with debris over the years and therefore needed some cleaning. The reason I referred you to the other thread was because I was unsure if you knoew the component make up of the fader. The 1200 fader is the same as the one in the thread, with only very slight differences. Functionally they are the same.

I'm not sure of the rubber inlay you are refering to - are you able to take and post photo's?. The internals of the fader (mine) are a piece of plastic, and the metal shaft that runs through it which the slider button/cap/knob thing fits on. There is a very thin piece of material which is only a dust trap that runs the length of the fader, and a ring of material which does the same thing under the slider knob. My fader moves smoothly, before it had the centre click, but I removed that when doing cleaning (quite easy). Perhaps the centre click is the resistance your refering to??

quote:

when i put it all back together and tried it out it still wasn't very smooth and i looked at it from the side and it looked like the contacts of the slider where pushed really hard to the contact board, thus creating a lot of friction between the two. what I stupidly did then was to change the slider (removing part of the upper structure) so that the contacts would be further apart, but now they are so loose that they don't make any contact at all sometimes.

Can you explain this in more detail. How are you looking at the contact? is the fader stripped to single pieces? I'm wondering if that may be the problem now.
I still need to do the fader on my 2nd deck, so when I get my camera, I'll do that like I did the other fader thread. It might help, but it won't be for a while yet.


As for the chip's being swapped, if your unsure, maybe get a local technician to do it, but if you have done soldering/desoldering it is a very simple task. Just be sure to put them in the same way they came out and your good to go. And don't over heat the chips.

Here's an image I found of one dismantled to give you an idea if you not sure

yeah, mine is different. it doesn't have the spring and it has a rubber inlay. plus it doesnt have any pins anymore since I broke them. (material failure I say, the second time I bent them they broke)

it does have 4 long pins though, that are soldered to the pcb board but don't do any electrical contact (this is I believe the older design but I'm not so sure)

no matter, I'll try to get a camera this weekend and take some pictures to make this clearer.

bye

Not sure if you mentioned it already,but what model do you have, ie mk2, mk3,etc?
The spring in the plastic also has a ball bearing and that is what creates the centre click position. removing it just allows a smoother slide, but the quatrz lock still works meaning you still have an inaccurate point around the zero mark. This can be disabled, but I'm yet to do it to see what it is like. There seems to be two methods for this, one of which seems a bit dodgy electronically.
So did you buy these new or 2nd? Did it look like someone else had done some work on the pitch slider befroe - ie desoldered it or anything?

I'm wondering if those broken pins may have caused the problem, or was it already faulty when you dismantled the thing the first time.