Monday, September 1, 2014

Refurbishing a Quad 303 on behalf

Recently an acquintance requested for assistance to refurbish his 303.

Externally it was in near mint condition.

These are the pictures of it internals.

View of the components on the top of the chasis
PSU board

Original RCA transistors
Condition of the large caps - one leaked with another two on the way (orange dots forming)
Original condition of the internals below the chasis
Close-up of the driver board with EC spillage

After recap and upgrading
The PSU board was functioning properly despite the damp looking surface. No humming from the transformer or any additional spillover near the PSU board. The PSU board output voltage was a bit higher than expected ... maybe cause of the large caps leakage after many years? After rebiasing the output voltage was stable over the period the unit was with me.

Only cleanup was necessary on the driver board with the spillage as the components seem to be within specifications - surprisingly!!!

The original 2x2000uF caps for power were replaced by a single 10000uF 100V United Chemicon - more than adequate for the purpose (proposed by another European electronics company). The 2x2000uF 100V caps for supplying power for audio purposes were replaced by 2x10000uF 63V Rubycon with a bypass (on each) for bass extension.

The carbon resistor on each of the driver boards were replaced with a metal film. A ceramic cap was replaced with an equivalent value silver mica. The EC on the 303 boards was recapped as per my other 303 except the EC utilised in the this case, were ELNA Stargates. 

Sounds great after the aging components has been given a new lease of life - clarity with detail across the board. Bass reproduction is now tighter and sounds more realistic.

Do note the internal cabling tend to be brittle. Hence please handle them with care