Bias trimpot set to max resistance first. This equals to min bias current.

Smaller bias current corresponds to smaller bias voltage on Vbe multiplier.
Simulation shows: correct Vbe voltage as 3.5V  (+4.5 upper, -1.0 lower - it's not
symmtrical).

Well, this simulation is a piece of crap.
Vbe voltage in real life is over 6V.
Also good to remeber that Vbe voltage will DIFFER with and without output FETs.

Note: The Nmos200 is limited to 50 volts maximum and suitable only for 8 & 4 ohm loads.
For the TO220 version minimum FET spec is Vds = 140v and Pd = 125 watt @ 25° C.
Minimum spec for TO247 version is Vds = 140v and Pd = 250 watt.

The setup is done without a load connected to the power amp module.
First check your work and make sure output devices are insulated from heatsink.

1. Remove fuses and replace with 100 ohm 5 watt resistors.

2. Make sure power supply polarity is correct and connect amp to power supply and turn on.

3. Check output offset voltage and adjust VR1 to achieve an offset of less than 10 mV.

4. All being well a place a voltmeter across one of the 100 ohm resistors.

5. Adjust VR2 to set the output stage bias current, by measuring the voltage across one
of the 100 ohm resistors. Adjust for a reading of 3 volts per output FET pair.
I.e; For a 2 FET board set for 3 volts. For a 6 FET board set for a voltage of 9 volts.
This equates to a bias current of 30mA per FET pair or 90 mA total.
For a 10 FET board set for a voltage of 15 volts.

6. All being well replace the 100 ohm resistors with 10 ohms 1 watt resistors and
re-adjust VR2 to get 0.3 volts per FET pair.

7. Once done, remove the resistors and put the fuses in.
Re-check the offset voltage and adjust with VR1 if necessary. The amp is ready. 



Instead of the 2SC1845 you could try these;

2SC2546, 2SC2547, 2SC1841, 2N5550, 2N5551, 2SC1845, 2SC2003, 2SC2784, 2SC2362, 2SC1775, 2SC2856,
2SD755, 2SD756.
Try to choose one with the lowest noise rating.

Replacements for MJE340 / 350
KSC3503 (PNP) / KSA 1381 (NPN)


R4, R5, R9, R12, R15 = 0.6v
R7 = 27.2v
R20 & R22 = between 3 to 4 volts depending on the FETs used.

BIAS: 30mA per pair (8mV on 0.22 emitter resistors)

BIAS spread voltage: 6.90V