[DMcMahon]

As per the schematic K5 is just a single switch, its bottom and top contact arms have 2 contacts each so on original brief look I thought it maybe was 2 separate switches.

K5 is normally open and it closes when a Uher rechargeable battery is fitted in the battery box and it connects the -ve battery contact out to pin 5 of the 6 pin DIN Accessories socket connector. Pin 5 is the charging supply from the Uher Z 124 / Z 124A / Z 124A1 power adaptor.

K5 is used in conjunction with K6 (normally closed), K6 connects the -ve supply from the Z 124 at pin 6 of the Accessories socket through to the battery -ve connection, i.e. same point K5 connects to.

K6 operates (opens) when DIN connector is plugged into the Accessories socket, this is to isolate the the Z 124 supply at pin 6 from connecting through to the battery box to isolate any fitted batteries or chargeable battery that may be fitted. Pin 6 also connects the Z 124 supply through to the main unit via K4.

I found that when DIN plug is plugged into the Accessories socket that K6 was not switching. K6 is mounted on a bracket directly above the right channel external speaker out 2 pin DIN socket and an operating lever from the switch goes across and enters a slot in the top of the Accessories socket.

The operating lever arm was sitting too high to be actuated when DIN plug was plugged in, found that K6 was sitting loose above its bracket, i.e. not fixed down. Removed K6 and found that it is riveted to the bracket but the rivets have parted company with the bracket.

I think this may explain why the battery box wires overheated etc If someone previously had either normal batteries or the rechargeable battery unit fitted and connected the Z 124 then K6 would not have isolated the batteries.

The problem now is to get K6 refitted, could try self tapping screws but I think the rivet holes through the K6 parts will be too small diameter for the screws to screw into the bracket. If not then maybe glue the switch down onto the bracket.

The Service manual has a set-up procedure for K6 which says to loosen the speaker DIN socket and adjust the switch bracket, this is nonsense because the bracket is glued to the case and not fitted to the speaker DIN so there is no adjustment possible.

David