20 WATTS 2 x EL84 MONO AMP. PARTS LIST AND SPECIFICATIONS:
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Rated Power Output: 20 Watts
Frequency Response: 30Hz - 15kHz (+/-3dB)
THD: 2% (1kHz/20W)
Signal to Noise: 85dB (Input Shorted)
Input Sensitivity: 500mV

RESISTORS:
R1,R5,R6,R7 = 1M
R2,R8 = 2.2k
R3,R9 = 220k
R4 = 560R
R6 = 150k
R9 = 220k
R10,R11,R14,R15 = 470k
R12,R13,R18,R19 = 110R
R16,R17 = 10R/0.5W
R20 = 100k
R21 = 22k
R22 = 15k
R30 = 33k

TR1,TR2 = 1M trimmpot
TR3 = 220R/0.25W wire wound trimpot.
L1 = lamp 10V 50mA


CAPACITORS:
C1 = 0.047uF/100V
C2,C5 = 47uF/16V
C3,C4 = 0.033uF/400V
C6 = 0.027uF/400V
C7 = 47uF/50V
C10 = 100uF/450V
C11 = 47uF/450V

T1 = Output Transformer - no data available
D1 = 1N4148

Power Transformer:
Secondary: 2 x 300VAC 125mA
Filament1: 6.3VAC/1.2A
Filament2: 6.3VAC/2A 

Tubes:
V1 = ECC83
V2,V3 = EL84
V4 = EZ81

Calibration Procedure:
Make sure all wiring and connections are correct. Remove tubes V2 and V3 from sockets,
leave only V1 inserted. Short amplifiers input to common ground.
1. Set both trimmpots TR1 and TR2 in center position.
2. Turn on power and check voltage at TP1, adjust with TR2 to ca. -20V. Next turn off power
and insert both power pentodes V2 & V3. 
3. Turn on power and let the tubes warm up. Connect DVM between the control grids of the 
pentodes, adjust with TR1 to zero Volts. Set DVM to 1 Volt scale and reset again to zero Volts.
4. Next connect DVM to common ground and one of the pentode cathodes, adjust with TR2 to 580mV
(0.58V).
5. Now connect DVM between the two pentode cathodes and adjust with TR1 to zero volts, use lower scale.
6. Finally measure voltage between common ground and cathodes of both pentodes. Should be 580 mV
+/- 20mV. Repeat steps 3-5 if needed.