The hour has finally come: The unit is ready. It is a different revision of
the Exponent 4-40 than the one that I had before. Probably pretty rare. This
one is point to point wired and thus it was quite difficult and extremely
time involved to work on it, as circuitry is constructed 3 dimensionally and
it was very hard to work on replacing parts at the lower levels, but I am
happy to report that all went well and that all is perfect now.
The amplifier in this unit sounds truly amazing rivaling expensive High End
amplifiers. The sweetest amp I have heard in a long time. The best solid
state amplifier I have heard thus far.
The photo shows: Front, Rear, amplifier inside, replaced electronics parts.
Work performed: Amplifier: Replaced all power supply and signal coupling
caps. Treated controls, contacts and switches with contact cleaner.
Record changer: cleaned and re-lubricated all mechanical parts. Replaced the
idler wheel. Re-worked drive surfaces. Mechanical adjustments. Casing:
Physical cleaning and detail work. Custom fabricated replacements for the
cable holders.
The '67 EXP-440 came in two different versions. One used a ceramic cartridge and an 8-transistor amp. The EXP-440-2 used a Pickering magnetic cartridge and a 12-transistor amp, 4-transistors for the additional phono pre-amp stage.
The phono pre-amp stage exclusively uses a common 26-volt DC supply voltage. If the 470-ohm 5-watt resistor feeding the 26-volt supply were to open up, it would kill both channels of the phono pre-amp and not affect the aux inputs.
Looking at the component side of the circuit board with the controls at the top, it's the only square, 5-watt wire wound resistor on the lower right side of the board, just above the main power supply rectifier diodes.
The phono pre-amp stage exclusively uses a common 26-volt DC supply voltage. If the 470-ohm 5-watt resistor feeding the 26-volt supply were to open up, it would kill both channels of the phono pre-amp and not affect the aux inputs.
Looking at the component side of the circuit board with the controls at the top, it's the only square, 5-watt wire wound resistor on the lower right side of the board, just above the main power supply rectifier diodes.
