Version 4
SHEET 1 4512 1860
WIRE -496 -80 -576 -80
WIRE -368 -80 -496 -80
WIRE -176 -80 -368 -80
WIRE -176 -64 -176 -80
WIRE -176 48 -176 16
WIRE -368 128 -368 -80
WIRE -176 176 -176 128
WIRE -176 176 -304 176
WIRE -176 256 -176 176
WIRE -576 304 -576 -80
WIRE -368 304 -368 224
WIRE -240 304 -368 304
WIRE -368 368 -368 304
WIRE -176 416 -176 352
WIRE 48 416 -176 416
WIRE -176 448 -176 416
WIRE 48 464 48 416
WIRE 144 480 96 480
WIRE -576 544 -576 384
WIRE -368 544 -368 448
WIRE -368 544 -576 544
WIRE -176 544 -176 528
WIRE -176 544 -368 544
WIRE -368 592 -368 544
WIRE 48 592 48 544
WIRE 96 592 96 528
WIRE 144 592 144 560
FLAG -368 592 0
FLAG -496 -80 UB
FLAG 48 592 0
FLAG 144 592 0
FLAG 96 592 0
SYMBOL voltage -576 288 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
WINDOW 3 24 96 Invisible 2
SYMATTR Value 185
SYMATTR InstName V1
SYMBOL res -192 432 R0
SYMATTR InstName R_Last
SYMATTR Value 30k
SYMBOL res -192 32 R0
SYMATTR InstName R2
SYMATTR Value {R_var}
SYMBOL pnp -304 224 R180
WINDOW 3 84 68 Invisible 2
SYMATTR InstName Q1
SYMATTR Value BC556B
SYMBOL pnp -240 352 M180
SYMATTR InstName Q2
SYMATTR Value MJE350
SYMBOL res -384 352 R0
SYMATTR InstName R3
SYMATTR Value 1000k
SYMBOL sw 48 560 R180
SYMATTR InstName S1
SYMATTR Value SW2
SYMBOL voltage 144 464 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value PULSE(0 5 0 0 0 200u 300u 3)
SYMBOL res -192 -80 R0
SYMATTR InstName R1
SYMATTR Value 90
TEXT -584 728 Left 2 !.tran 2m
TEXT 184 -72 Left 1 !.MODEL MJE350 pnp\n+ IS = 2.7544E-13\n+ BF = 134\n+ BR = 0.092\n+ ISE = 9.0546E-14\n+ NE = 1.5\n+ ISC = 5.24807E-13\n+ NC = 2\n+ VAF = 100\n+ VAR = 100\n+ IKF = 0.4063\n+ IKR = 0.57544\n+ RB = 0.18\n+ RE = 0.018\n+ RC = 3.72\n+ CJE = 9.572E-12\n+ VJE = 0.748\n+ MJE = 0.371\n+ FC = 0.5\n+ CJC = 1.147E-11\n+ VJC = 0.541\n+ MJC = 0.329\n+ TF = 8.262E-10\n+ XTB = 0.907\n+ EG = 0.62\n+ XTI = 3
TEXT -584 648 Left 2 !.model SW2 SW(Ron=1 Roff=1G  Vt=0.5 Vh=10m)
TEXT -584 688 Left 2 !.step param R_var 1 50 10
TEXT -64 288 Left 2 ;300V, 15W, DPAK
TEXT -120 72 Left 2 ;"Trimmer, 50R, 20 Gang"
TEXT -496 104 Left 2 ;MMTA92
TEXT -536 136 Left 2 ;300V, 350mW