Alchemist Forseti APD15A RC Integrated amplifier Using Pic

Alchemist Forseti APD15A RC Integrated amplifier

We recently had a customer present this faulty Alchemist Forseti integrated amp for repair – I’d guess this dates from the 1990’s and has been well looked after. It’s a bit of a bruiser as you can see from the extensive heatsinking!Alchemist Forseti APD15A RC Integrated amplifier

Unfortunately it developed a DC fault on the loudspeaker outputs and destroyed the customers speakers, so it’s now in the naughty corner awaiting surgery.

Access to the internal circuitry is via the top panel, which is secured by 13 cap head screws.

There are 13 screws to remove in total, an allen key is needed.

The rear panel has good connectivity for analogue sources (all line level, no phono input  but there are two pre-outputs to drive extra power amps should you need even more power.

Once the top panel is removed, this is the view of the printed circuit boards and power supplies – it’s very nicely laid out.

The Forseti is constructed as a dual mono design, which should give better channel separation and therefore improved stereo image – here is one channel’s output stage which employs two pairs of output transistors per channel – 2SA1302 are the PNP transistors and 2SC3281 are the NPN making a class B push pull output stage.

Each amplifier channel is fed power from it’s own dedicated power supply comprising 200VA toroidal mains transformer, bridge rectifier and four 10000uF/ 50V resevoir capacitors.Alchemis Forseti APD15A RC Integrated amplifier schematic

Leave a Comment

Your email address will not be published. Required fields are marked *