JELCO 750, a special mono version!

Latest interesting tonearm to come my way (nice to break the rega monotony) is a Jelco 750, now there must be a LOT of these arms floating around the world, a classic Japanese arm that many of you will know about and even own...

Of course not many of them would be mono! 🤔 And of course neither should this one be, but unfortunately the left channel was missing, from the headshell mounting pins to the DIN plug, the left channel was MIA...

Nice thing with the Jelcos is they come apart relatively logically, some of the assembly is very similar to the Micro 505, so with tools in hand I dove in.

The base section hold the DIN plug, and provides the mounting base, removing this leaves one with a bare machanism showing, and the DIN plug hanging out in the open.

At the other end we have the bayonet mount, this requires a little more care, as they are glued in you need some heat to help get them loose once the retaining screw is removed.

So headshell end doesn't look too bad, connections were all ok for the wires to pins.

Moving back to the armbase end I started tugging at the wires to see if they would move at the headshell end. Funnily enough the white one did nothing at the headshell end and pulling on it saw it come straight out from the yolk area!

The wire appears squashed, my guess its gotten caught up somewhere inside the mechanism and over time has broken through. In order to rewire the arm neatly, the vertical bearings need to be disassembled. Its not as bad as it sounds, as they are preset in the base disc its realtively straigthforward to remove the base disc, the silicon damping frame that sits above the yolk, and then lift the lower frame off the yolk leaving us with what you see below...

Getting to this stage revealed another issue, the main earth wire to the arm wand was also squashed, the pic above shows the wire in its sad state, cannot be left like this!

So next up remove the wand from the yolk body. Its easy to remove, and what you find is a brass insert in the end with the earth wire soldered deep in at the other end of the brass! It would be silly to try and remove the brass simply to solder to the back edge of it, so better to solder to the part that is visible, even though its not the easiest thing to solder neatly due to the heat soak into the wand, I managed to solder a new piece of Superflex tonearm wire in place.

With this done, the arm wand was fitted back into the Yolk body, then new Superflex arm wire was threaded through the arm and up out the guide hole on the bearing plate, the plate was then juggled into place and screwed back down, bearings are still nice and smooth with no play.

The DIN plug was then soldered back into place, the second earth wire that goes to the bearing plate was replaced, and the wiring at the base end was sorted.

Last up was to refit the headshell bayonet mount, Superflex soldered into place the the little clear plastic tubes back over the pins to protect the solder join area.

The bayonet mount was refitted with a spot of glue again, in order to avoid any twisting movement when headshells are removed and refitted. The screw hole is slightly bigger than the screw so there is a small potential for the bayonet to be twisted slighty to one side or the other and you dont want to be doing this little screw up crazy tight and strip threads!

With the base section refitted and the DIN plug back in place with its grub screw retainer, the arm is now stereo and ready to go back into service, likely sounding better as well with the new hi grade KAB Superflex wiring!