That is a very common relay so most mayor electronic companies have them.
Mouser, RS-Electronics, Element-14, Digikey, etc. just google G5V-1 relay.
If it was the relay not working then the LED's should still work.
I still think you are loosing power somewhere between the 58V (B)and the earth end of the 2k2 resistor.
If I am correct that the LED's are swapped on the schematic and terminal X has to be connected to earth for the overdrive to be on then the problem would be between the 58V and the grounding on the treble pot switch or the foot switch jack.
Are you using the treble pot or the foot switch to select the overdrive channel ?
If you are using the treble pot then try the foot switch instead and see what happens.
If you do not have a foot switch then insert a normal mono plug into the footswitch jack as this should work as well. (guitar lead will do)
Try the opposite of what you have been using to try to eliminate the fault.
It might be a bad part or component, but more likely a solder joint that has gone bad over time from vibrations.
Mouser, RS-Electronics, Element-14, Digikey, etc. just google G5V-1 relay.
If it was the relay not working then the LED's should still work.
I still think you are loosing power somewhere between the 58V (B)and the earth end of the 2k2 resistor.
If I am correct that the LED's are swapped on the schematic and terminal X has to be connected to earth for the overdrive to be on then the problem would be between the 58V and the grounding on the treble pot switch or the foot switch jack.
Are you using the treble pot or the foot switch to select the overdrive channel ?
If you are using the treble pot then try the foot switch instead and see what happens.
If you do not have a foot switch then insert a normal mono plug into the footswitch jack as this should work as well. (guitar lead will do)
Try the opposite of what you have been using to try to eliminate the fault.
It might be a bad part or component, but more likely a solder joint that has gone bad over time from vibrations.