Mad Axe Amps was kindled from the decision to re-condition an old valve amp originally built in the 1960’s by a family member.
The design (I later discovered) was based on the re-cycled guts of an old reel-to-reel tape recorder. Inside are four valves; 1x EF86, 1x ECC81, 1x ECC83 and an ECL86. The last valve is a triode-pentode unit, designed specifically for low power, compact systems of the day.
Mains transformer, selenium rectifier and smoothing capacitor. The rectifier seemed ok, so left as-is. The orange capacitor was way past use – dried out and not measuring the 50-50-50 uF it should have been!
Dodgy wiring, dried-out capacitors, noisy pots and an odd output stage meant a few things needing doing!
An odd board – only the right hand valve socket was used, fitted with the ECL86. Most of the other components on the left were not needed! Uncoventional design in that the power supply fed through this output stage board to the pre-amp section mounted at the top of the amp cabinet. Oddly, despite this, the amp is fairly quiet in respect mains noise.
Due to availability and cost, the original ECL86 was replaced with an ECL83 on a Mad Axe Amps custom circuit board. This valve has a different pin-out, so required a new circuit, providing the chance to replace the dried out smoothing capacity with a new bank of three. Mains and output transformers have been re-used.
Pots were replaced and several electrolytic capacitors on the pre-amp board before re-assembling with the new output board. A new mains cable socket and fuse has been fitted to a new back panel, not shown here. This also allows for mounting of the headphone output, currently swinging free in the picture.