A nice restoration project for a friend. He bought this mysterious vintage Mac amp which needed some care. These were made in Italy probably around the 70’s and are supposedly similar to the Vox AC30. They both use 4 EL84s in the output section but their similarities end there since the MAC is actually an early hybrid amp with transistors in the preamp stage!
First of all the front panel needed a good cleaning and many of the potentiometers were stuck from dirt and oxidation so the knobs had to be removed.
Some of the pots, especially the ones for the reverb, were seriously damaged mechanically but because of the way they are built they’re easy to repair if the resistive surface is still good. Suprisingly, after some cleaning all the pots were working as they should. With the exception of the bypass switch, the rest of the toggle switches were repairable too.
After that I replaced the power filter caps and all the four channels were playing loud and clear with their controls fully functional. The only problem now was the spring reverb which was not reverbarating with the guitar but it could be heard if the tank was knocked. It showed a problem probably with the input and sure enough the input transducer coil was damaged. I ended up rewinding the coil with wire from a broken guitar pickup and the reverb came back to life!