The only thing that can really be tested is the gating circuit.

1. Power up the main board by connecting J4 as before.
2. Clip one end of an alligator clip to the south side of R146 (gate).
   
3. Connect the other end to the exposed side of R3 on the IO board (which provides +5V)
   
4. Check the voltage at the north side of where D35 goes, using a scope or meter. When the clip is connected, there should be 12V. When its not connected, there should be 0V.
   
5. Check the voltage at the top of where D36 goes . When the clip from R146 is disconnected and touched to R3 again, there should be a brief pulse to 12V, if your meter has a 'max hold' setting, you can use this to see whether there is a pulse. (The picture shows testing after the VCA has been installed, but just ignore that)
   

 

 

	1N4148	5	D26, D28, D29, D34, D37
	22 ohm 5% resistor	1	R150
	100 ohm 5% resistor	1	R152
	1K 5% resistor	1	R137
	10K 5% resistor	6	R142, R143, R144, R145, R148, R149
	22K 5% resistor	3	R117, R146, R151
	68K 5% resistor	1	R138
	100K 5% resistor	3	R139, R140, R141
	1Meg A (log) dual potentiometer	1	VR6
	.047uF (2A473K) capacitor	1	C54
	1uF tantalum capacitor	1	C62
	10uF electrolytic capacitor	1	C72
	47uF electrolytic capacitor	1	C55
	2SA733P, TO-92 PNP transistor	2	Q36, Q38
	2SC536F, TO-92 NPN transistor	4	Q35, Q37, Q40, Q41
	2SK30 JFET, must be 2SK30AY	1	Q39