3-channel Audio Amplifier circuit

Careful examination of the photos of the amplifier will reveal that the heatsink on the HY60 near-clone I built using the TDA2050A is slightly shorter than that on the original HY60s. I placed this unit at the rear of the amplifier, and the gap provides adequate space for a free-flow of air up the inside of the amplifier. No slots were cut in the bottom-side of the top slab, this is lined up and held firmly in place with three large woodscrews driven through the middle-tier upwards.
3-channel Audio Amplifier circuit - schematic

Safety should be paramount where mains voltages are concerned, and each Brass panel is connected with stoutish insulated wire to the brass panel on the PSU to which the Earth from the mains supply is connected. This was then connected via a 100 ohm resistor to the 0v line of the PSU. A similar wire connected to the transformer pan base is also connected to Earth. For the 0v line on the PSU I used a small-diameter brass bar, which allows connections from the amplifier at any point in 360 degs. The +ve and -ve connections were done using reasonably heavy (10 amp) insulated wire. Look carefully at my photos of the PSU and you will see that a change of mind resulted in me cross-connecting colours on the capacitors, so that I ended up with a RED -ve wire and a BLUE +ve wire – don’t do this at home! To have fitted two 20,000uF capacitors would have resulted in a larger case, so I substituted these for two sets of 3 X 6800uF, and sited these by drilling receptacles in the base slab using a Forstner bit. The bridge rectifier is fastened to one of the small Brass panels using a little silicone grease to aid cooling. Note that I made the transformer pan cut-out slightly larger than the Tx itself, to allow for the free flow of air around the periphery, via holes drilled in the pan base. The transformer (which I bought from RS components) came without a fitting kit (I had assumed this was included). I improvised bottom and top...

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