Friday 5 August 2016

Arcadia 7W PSE 2A3 Power Amplifier Upgrade

At the end of last year one of the original SJS Arcadia 7W PSE 2A3 amplifiers, originally built back in 1998, came in for a major service and upgrade.

Following the terminal exit of the main power transformer the opportunity was taken to upgrade and almost rebuild it.

The main power transformer was replaced by an external dual mono PSU, containing 6 mains transformers; two for the HT to the 2A3 power valves, two for the HT to the 6072A-5687 input/driver stage, and two for the negative bias supply for the grids of the 2A3s.

EZ81 rectifiers, choke input and first smoothing cap for the input/driver stage power supply are inside the PSU case

Four umbilical cables connect the psu to the audio chassis

Independent left and right mains switches, with remote switching controlled form the audio chassis

Removal of the power transformer from the audio chassis allowed for a pair of larger chokes to be fitted for the 2A3 HT supply, each channel has NOS GZ37 choke input supply and Elna Cerafine HT caps in the HT, and NOS Mullard EZ81 and choke input supply for the bias supply

Inside there was a major component refresh and upgrade; tantalum resistors, Hovland Musicaps, lots of Black Gates, Jensen 4 pole HT caps, Kemet bias supply caps and silver wiring

Not looking to shabby for it's age, and now fit and ready to go

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