Technics SL1200 / 1210 Speed Fluctuation Problem
I've found this site whilst trying to research a problem I have with my technics SL1210 Mk2. I've searched the forum but can't find anyone describing the subtle speed changes I am experiencing.
I have two of these decks, for DJ'ing, but recently one of the decks has developed a fault where the speed constantly oscillates around what I presume is the speed it should be turning at.
This isn't audibly noticable, but it causes huge problems when trying to beat match records as one record drifts all over the place and continual correction of this 'drift' means the mix will never actually sound cohesive.
The fluctuation is in the order of tenths of a percent, and occurs at all positions of the pitch fader, including at the zero position. I have come to this conclusion by playing two copies of the same record and hearing it drift from being in time, to too fast, to back in time, to too slow, etc., etc., so I'm pretty certain this is what is happening.
I've put a new pitch fader in the deck anyway as it is 15 years old and never needed servicing, but I guess something else is wrong and causing this problem... I am very willing and able with a soldering iron, but I don't have anything other than basic test equipment, i.e. a multimeter. I'm up for replacing as much stuff as it takes to fix this problem and have a bit of a stock of capacitors, etc.
If anyone can offer any advice it would be seriously appreciated as I don't have the time to send the deck off for repair anywhere.
did you read this? http://www.diyaudio.com/forums/showt...026&highlight=
Never needed servicing? What a joke, so you never oil your car parts or put oil in the engine
, it has to break down first?.... Your spindle has never been old, tonearmclean and servived, so you have the cheap rca's. Never changed some elco's en the cheap potentiometre on the board, which a few people change but is a throw away thing. Just clean or better replace the pitchfader and clean the table, but after 15 years , i just would place new bearings in the tonearm and replace the tonearmwire and rca's and don't take technics ones. Your car also needs to be serviced every year by law.....
if You switch on Quartz lock is there still fluctuation?
If not, one can already exclude Magnet weakening and FG-coil related probs.
Then the issue may be related to the circuitry around IC301 (AN6682) and IC302 (MN4011B) on the Motor-PCB including the Pitch-Fader-PCB.
For Service manual look at the VinylEngineŽs Database.
Additionally You can find a "Help-Sheet" with pics of the Motor-PCB and the location of components at deckdoctor.com.au and djsdeckdoctor.com
Also have a look at KAB Electro Acoustics http://www.kabusa.com and the Problem#1, related to Diode D301.
ps. KAB erred with their correction schem of the Pitch Fader".
Compare the schematic and the PCB-Layout and YouŽll see that the Technics Manual is correct.
Clean the speed pots with Deoxit 5 spray cleaner. It may just be dirty pots. You will have to removed the bottom cover perhaps the motor board to gain access to the speed adjust pots.
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