UK, 240V low power practise amp with 2 wire cable and no earth wire.
Loud mains hash but finger touch the metal chassis and mains hash noise
goes. To a lesser extent of noise reduction , touching guitar body( via
guitar lead). 0V of 12-0-12 Tx secondary to chassis ground.
6 100nF, 25V disc ceramics between various points and chassis.
Ground lines are all fine, input socket fine.
Battery powered source , into aux input, is fine , no hash.
Someone has been inside messing about, but nothing obviously missing.
As found, the plastic barrel Jalco guitar input socket, does not have a
local bond to ground. So i created one and cut the ground line from Prea
to PS+PA , as that line is over 1 foot long, no change to mains hash.
What is the function of heatsink insulator fibre reinforced matting
between Tx and chassis under the 2 mounting flanges, held with 2 steel
bolts and washers, damps acoustic resonanace/vibration?
Other than replace the 2 core mains cable with 3 core ,any ideas ?