I need to get my sl-dz1200 back to business ascap

http://sparedparts.com/products/technics-sl-dz1200-service-manual-complete

You need to get the updates from the manufcatures web site.

Technics SL DZ1200 MKII Mod Fixing Flawed Design DJ TechTools

A lot of issues with this unit

try loading the audio again on your computer. maybe it didn't load properly. also try switching the technics deck off and back on. maybe it is having a bad day and needs to restart.

https://www.vintageshifi.com/repertoire-pdf/pdf/telecharge.php?pdf=Technics-SLDZ-1200-Service-Manual.pdf
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As a DJ myself, I have seen that before. On a night that the equipment will not be used, UNPLUG ALL CABLES AND POWER, then use an eyedropper to drip a drop or 2 of water on the spindle and manually spin the table a few turns., wait about 5 minutes, then drop a couple drops of rubbing alcohol and again spin the table. Wait a couple hours or over night, and follow with a couple drops of oil. NO MORE THAN 3 DROPS OF ANY OF THESE!!

There might be something in the reader that needs to cleaned out. Or the cd reader itself might be damaged. In either case, you'll need professional help.

- OPTiC
DJ Equipment Repair & Service
A DJ Pro Audio Co.

THEY HAVE THE PARTS AT PANASONIC.COM. THEY SHIP ANY WHERE....JUST TYPE IN MODEL#...

Found a video on a web site "how to remove the platter". It's a job which does'nt need a lot of skill just great care and patience. Within the video the guy will show the senors inside the platter itself. This is wear I found a huge build up dust which I blew off with a can of air. It's not a proffensional video but I found it very easy to follow. Unfortunate for though upon putting the deck back together again I've caused more damage with my clumsy haevy handed inpatience! After looking inside the deck (as long as you have no warranty left) you will see it is not that difficult and as a tip you can disconnect the lines of flat wires as they plug into the circuit board and are not soldered in. No soldering required to fix this. The guy who made this video deserves a lot of credit due to the fact he can save many of these decks from going to the bin! If I was rich and famous I would award him an Enviromental Gong.