Apex hv23
- Thread starter SR-been
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SR-been
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As you can see,there are two kind of schematics:with 2SA/2SC to92 transistors and the other with 2N/BC/MJ to92 transistors. The pcb´s are routed for the 2SA/2SSC version so if you plan to do it with BC/2N/MJ transistors you must pay attention to a difrence in pinout for those transistors. Just compare schematics with pcb layout and that is a bit longer but much safer way for you to reach working amplifier from first pluging in.
SR-been
New member
The other thing interestig with this amplifier is the protection-psu-soft-start pcb of PSU7 that comes with it. That PCBoard has on it dc-protection,speaker delay of few seconds,overload protection,soft-start for the transformer primary and PSU with 40 000uF capacitors wich is enough for stereo APEX HV23. In just three pcb´s you have fully functional amplifier with all the protections.
SR-been
New member
One more thing important for assembling this amplifier is that you should match all input pairs of 2N5401/5551 or 2SA970/2SC2240,in order to reach nice simetry. In my case i have reached 12mV at one chanel and about 45mV at the other(wich i plan to make smaller/better). I did it just using regular digital multi meter-no special methods.
SR-been
New member
The recomended bias for the amp is 20-50mA per output pair,but i haven´te noticed any diference between higher and lower value so it is set on 20mA when it reaches working temperature. This amp should be set for bias in a few steps:bias will be at higher value when the amp is cold so it should be monitored on the sors resistor that gives the highest value of voltage drop. Place the leads of voltmeter with crocodile clamps on that resistor and follow the value of voltage. Using Ohm´s law U=R x I = (0,47 x 0,02) V adjust the bias untill it stops droping down. Than you can begin to use this amp at full power. If in any case you can not reach 20mA bias,just replace 470R trim. with 1k trim. and you will be able to reach much more. It is atentionally put that way for safety of burning output transistors because it is mentioned that a lot of beginers will do this amp for them self.
Enjoj!
Enjoj!
