SONY TC-K850ES: Servicing the Mechanical Block
I described the procedure in Article #6 of the TC-K555ESA mechanical block restoration. Thus I won't explicitly repeat the steps in this article. But I took pictures.
This is the mechanical block.
View from another angle. Notice the non-standard capstan belt.
Detailed view. We can see that the belt is not stepping inside the machined guidance on the take-up side capstan flywheel. Nonetheless the deck worked pretty well.
I decided to change the electrolytic capacitors on the two PCBs that are attached to the mechanical block.
Parts have been changed.
...PICTURE FOLLOWS SOON...
This deck however suffers from electrolyte leakage on the capstan motor controller PCB. The electrolyte from one of the 10 uF filtering capacitors partially ate away copper traces and I was forced to chemically and mechanically clean everything very well. The result is that part of one track disappeared completely.
I have used MLCC parts as replacements. Carefully thinking length and bending leads solved the missing track problem as well. It doesn't look that beautiful but it is functional. Notice the weird dot-like black spots next to the missing trace. That is some kind of corrosion which I failed to remove.
Here's a different angle view.
The mechanical block is stripped of the plastic ornamental plate. Both pinch rollers are out already.
The old supply side pinch roller is removed with my improvised rig. The new one is ready to be mounted in.
In the end, every subsystem of the mechanical block went back in reverse order. Then the mechanical block is ready to be mounted back in the deck.
The new capstan belt steps right in the machined guidance gutter on the take-up side flywheel.
At the end I secured the alignment nut with some nail polish.
And a picture with the flash activated so that you can see the new pinch rollers in their final position.
So far so good. The mechanical block is very stable. Again I have tested ferric, chrome, and metal tapes. All run smooth without skewing.