gres
Full Member level 4
I need strong, armoured amplifier with complete safety system that guaranteed long safe work for power amp and loudspeakers.
Power amp ending.
Holton 800 (AV800) after upgrades with bipolar power transistors, six pars pair side. Transistors are popular and best one - 2SC5200 and 2SA1943.
PCB
Boards were design in paint. Adjust indicator come from old skytec 240pro amplifier, I had to calibrate.
Casing
Is made by metal galvanized sheets that used to were BIN cereal silos. Casing is create by hummer, shears, drill, vice. Casing is strong durability and rust-proof. Casing is fit to rack, high 3U. i'm afraid that spray paint won't work good so i'm going to paint it in comminution way.
Cooler system
For transistors cooling responsible are 2 radiators - dimensions: 33x13x3,5cm. I used silicone washers and thermo- conduct paste. Temperature safety systems are set to 700C. When it works with full power, they not going to burn you so everything seems to be fine.
Power supply
For power supply responsible are 2 toroidal transformers 600VA and voltage 2x65V AC each in dual mono version. Rectify bridges are flat 25A/1kV. For filtration responsible are condensers 8x3300uF/ 100V per channel. After filter there is about 91V
Safety system
Thermal - 700C
Short circuit ( adjustable 2A to 10A)
Overload ( 2A to 10A)
Late loudspeakers column start - about 5-7 sec
Fast disconnect loudspeakers
Against DC and unsymmetrical amplitudes
Soft start
Limiter that can shoot down amplifier.
Power and parameters:
Wedge ~20kg
Power 2x550W RMS/4R ( power amp ending can hold up to 2x800W/4R but transformers are too weak)
2x300W RMS/8R
Power consumption about 1500W max
Minimal impedance 2,7R
Voltage amplification about 45x
Resting current 100mA after get right heat 70-80mA
More info at https://www.elektroda.pl/rtvforum/topic1463062.html