Amazing spring reverb that was bought of ebay broken, because of its size I had to fix it on site. It was producing no sound at all (most equipment has a certain amount of hiss.)
Then after a bit of testing I discovered there was no power supply voltage at all. After a bit of dismantling I managed to get to the PSU PCB which is relatively a simple (to the rest of the unit) 2 diode full wave rectifier. Basically what had happened was the (west German!) electrolytic’s had completely shorted burning out the resistor.
So then it was just the case of taking it back to the workshop and replacing all the burnt out parts .. then with a bit of re-fitting it was alive!!
Here is the sound clip made by the owner, its a very tasty reverb …. maybe not worth the space it takes up!!
Amazingly AKG Still provide a support service manual for the BX-20 found here