Why not just add to this thread, since you already have it here?
I would be interested in this, since as
@coonmanx stated, I just bought another one. Here is a link to my previous restoration thread :
https://audiokarma.org/forums/threads/technics-su-v85a-amplifier-restoration.963896/
The pot shaft
First we need to fill up the Alps slot with I mm aluminium material. This was JB weld on. Then make a precision ring to fit the Technics faceplate and 6mm Alps shaft. The height of this part is 3.2mm. Outer diameter is 6.9mm, inside diameter is 6mm.This part is to perfectly center the volume pot. I think you can get away with this but the Alps will be a bit fiddly. While the glue is cross link curing, we need to make a half clamp with a 5.5mm hole. This part helps to clamp the pot safely without destroying it. Pics are there to show the 1mm and half clamp. I don't know how others can work on the pot safely without destroying it. Remove the excess material after the glue has cured. And check the diameter for exactly 6mm. This part is important as the volume dial is exactly this dimension.
The D profile
The D profile is exactly 4.5mm from the flat to the opposite curve part of the shaft. More for a tight fit, 4.55mm. Then shorten the shaft by exactly 4.5mm in length. Test fit with volume dial.
The Polycarbonate piece
Make a polycarbonate rest to support the pot against the pcb. The dimension is 26.87mm width by 10.1mm height by 5mm thick. It needs a recessed groove to clear the wires later at the front behind its cleared. This plastic also gives rigidity support to the pot when the EMI shield box is soldered back on. The width is a bit bigger than the opening of the EMI metal box. Remember to shrink wrap the pot, you want zero chips and diry going in there.
The enamelled wire
The alignment of the Alps pot relative to the Amp's face plate and the shield box resulted in the 6 pins very close to the small PCB . Using wires is not possible. You know these vintage mods hurdles need to be solved on the go approach. I used 0.6mm enamelled wires, its overkill for signal that is only microamps or just milliamps but that's what I have and it was surprisingly stiff when all six were soldered.Scrape off enamelled coating using a very sharp blade all around the wire that needs to make good solder contact with the six pins. Make a loop then soldered it flat against the exterior part of the pin since the polycarbonate is in between the rows of 3 pins. Do for all 6 pins. Check for continuity and cold solder joins using scope.
The EMI shield box
File the shield box a little only 2mm to allow the anti rotation tab of the Alps to just protrude out and make contact with the box. This is important as it grounds the pot to stop humming noise. The box is important as it acts as a Faraday cage against unwanted signal from the transformer. I saw another post that did not put this box back, I wonder if I was wrong about this. You want to file it carefully so that it's a snug fit use a set of good needle files. Test fit the box and it should sit proud slightly over the front of the pcb and not touching any of the 3 pins in front. It will short the whole board if it did. Mine was way far off. I didn't take a pic to show this part. When its done it looks like this. See pics attached. Oh yes scrape the wires then solder to the board. Then solder back the 5 ribbon cable. I ditch the original wires and used sillicon ribbon cable, gave it extra length do its not straining on the small pcb. Then put the pot into the faceplate and secure with a nut. Tighten a bit will do, then push the volume dial back and connect back all other connectors. Dim bulb connected just in case. It glows then fades off immediately. The scratchy sound is gone at minimum volume, the sound is amazingly good, I played on CD a similar music I listen to very often and could hear a significant difference, the musical instrument could be vividly identified easily, or is this a placebo effect? If you have questions on this restoration, I will try to answer them. Its not easy if you want to do this, a lot of planning ahead and foresight but I just had to do it. The old pot was measuring higher than the other side at min which explains why it never zero out the sound.
