Was this Beogram moved to a different mains voltage area? Replace the transformer and make sure it is set up correctly for the actual local mains voltage before connecting mains. Having siad that - if the Beogram suffered an over-voltage situation, some of the electronics may also have been damaged. Martin

A quick update on the Beogram's origin: found a serial label inside the user guide! There is also a white label inside underneath the aluminium.  

Update: Well well what a fun little journey that was 😀 I am now the exceedingly happy owner of a fully working and stunning Beogram 6500! So as @Dillen suggested I found a replacement transformer from a well known auction website for sixty five pounds. It came supplied with a fused circuit board (with the large capacitor) but had different traces to the one on my Beogram so I just soldered the new transformer to the original board and fitted it. When power was added the Beogram was alive. It wouldn’t track though. This baffled me for ages - until I decided to open up my Beogram 3500 to use as a reference. After checking the two I noticed the wires for the lamp were connected to the two pins for the motor, and vice-versa. I changed them over and presto the deck operated as normal. Next up I had to raise the platter to the correct height. Then the arm followed by the tonearm. Finally I adjusted the drop point because the stylus was slipping off the record at the start. (Worst nightmare) The tracking weight was set at over 1.5 so I pulled that back to just on 1. Big moment. Connected the Beogram up to the BM and sat for the next couple of hours enjoying some of my favourite LPs 😎 As always, I couldn’t have done this without the years of knowledge, resources and friendly people on this site to give me the confidence to try. (Two photos - the ‘how lucky am I?’ using one Beogram to check against the other scenario. And the BG6500 up and running at last ❤️)