This Polytone Minibrute Repair came in from a Lincoln customer with an obnoxious hum problem. This unit is probably form the 1980s
The issue was solved by adjusting the output stage bias point and improving the connection between the screw mount power supply capacitors and the power amp stage.
The amp is a bit of an oddball in terms of construction, with the preamp contained in the top of the amp, and the power amp in the base of the unit. The power amp unit is held together by the capacitor screws and two large heatsinks.
If you need a polytone minibrute repair, please get in touch.