Enclosure not stated · 4 knobs

WEM (Watkins) Project V Fuzz

Category: Fuzz
Controls: Volume · Attack · Drive · Edge
Price: see vendor
Also as: Vero layout · from Revolution Deux
Tags: freestompboxes.org trace

Read the post at Revolution Deux Schematic image D*A*M forum thread freestompboxes.org thread Vero layout

From the vendor

A rare vintage British fuzz from WEM in a very long case, owned by Graham of the D*A*M forum, who ranks it beside the Buzzaround. The circuit is unusual: an input pair with a small HF inductor in the first transistor's emitter feeds the Attack pot, then a multi-transistor gain and output section with low-value emitter resistors, while the Drive and Edge slide switches reconfigure filtering and feedback around the input and output.

The 470p capacitor can be 390p and the two 4.7 ohm resistors can be 5.1 ohm (alternatives on the drawing). The Q7 and Q8 BC108B positions (and Q6) can use BC109B. The layout notes say the inductor is optional and can be replaced with a jumper, or with a TDK EL0606 series or similar of under 10 ohms. The layout adds an optional 220p capacitor (its C17) that tames the fuzz's harshness, silver mica recommended.

Schematic

The schematic is in the post. Open it at Revolution Deux. No KiCad fragment has been drawn for this circuit yet.

Parts list 53 rows

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Check before you build · 3 values the reader of this schematic was not sure of

The schematic marks circled components as unknown values: the 2K2 trimmer at Q4's collector and the 6n8 capacitor on the Edge switch (drawn '6n8?').
The resistor across the Drive switch reads 150K; the verified layout's parts list has a 47K in what may be that position.
The layout's parts list substitutes MPSA18 for the BC108B transistors and 2N5087 for the BC186, has a 1.5M resistor (R24) not obvious on the schematic, and deletes a capacitor (its C2).

Ref	Value	Normalized	Type	Notes
Resistors 23
R1	390	390		supply; read from the schematic by eye
R2	100	100		Q2 emitter; read from the schematic by eye
R3	2.2K	2.2k		read from the schematic by eye
R4	10K	10k		Q1 collector; read from the schematic by eye
R5	1.5M	1.5M		feedback; read from the schematic by eye
R6	22K	22k		read from the schematic by eye
R7	10K	10k		Q3 base bias; read from the schematic by eye
R8	1.5K	1.5k		Q3 emitter; read from the schematic by eye
R9	330	330		Q4 emitter; read from the schematic by eye
R10	27K	27k		read from the schematic by eye
R11	1.5K	1.5k		read from the schematic by eye
R12	1.5K	1.5k		read from the schematic by eye
R13	100K	100k		read from the schematic by eye
R14	1.5K	1.5k		Q7 emitter; read from the schematic by eye
R15	4.7	4.7		alt. 5.1; read from the schematic by eye
R16	4.7	4.7		alt. 5.1; read from the schematic by eye
R17	1.5K	1.5k		Q6 base; read from the schematic by eye
R18	10K	10k		Edge switch; read from the schematic by eye
R19	4.7K	4.7k		Drive switch; read from the schematic by eye
R20	4.7K	4.7k		Drive switch; read from the schematic by eye
R21	150K	150k		Drive switch; read from the schematic by eye
R22	5.6K	5.6k		read from the schematic by eye
R23	10K	10k		output to ground; read from the schematic by eye
Capacitors 15
C1	1000u	1m		electrolytic; read from the schematic by eye
C2	47n	47n		read from the schematic by eye
C3	2.5u	2.5u		electrolytic, 64V, input; read from the schematic by eye
C4	50u	50u		electrolytic, 25V; read from the schematic by eye
C5	2.5u	2.5u		electrolytic, 64V; read from the schematic by eye
C6	2.5u	2.5u		electrolytic, 64V; read from the schematic by eye
C7	2.5u	2.5u		electrolytic, 25V; read from the schematic by eye
C8	50u	50u		electrolytic, 6.4V; read from the schematic by eye
C9	25u	25u		electrolytic, 25V; read from the schematic by eye
C10	22p	22p		read from the schematic by eye
C11	470p	470p		alt. 390p; read from the schematic by eye
C12	320u	320u		electrolytic, 6.4V; read from the schematic by eye
C13	6.8n	6.8n		input jack; read from the schematic by eye
C14	10n	10n		Edge switch; read from the schematic by eye
C15	6.8n	6.8n		Edge switch, value unknown (drawn 6n8?); read from the schematic by eye
Transistors 8
Q1	BC108B	BC108B		read from the schematic by eye
Q2	BC108B	BC108B		read from the schematic by eye
Q3	BC108B	BC108B		read from the schematic by eye
Q4	BC108B	BC108B		read from the schematic by eye
Q5	BC186	BC186		PNP; read from the schematic by eye
Q6	BC108B	BC108B		alt. BC109B; read from the schematic by eye
Q7	BC108B	BC108B		alt. BC109B; read from the schematic by eye
Q8	BC108B	BC108B		alt. BC109B; read from the schematic by eye
Inductors 1
L1	?	?		RS Components HF inductor, value unknown; read from the schematic by eye
Potentiometers 4
Trim A	50K	50k	Potentiometer	trimmer, set at about 22K; read from the schematic by eye
Trim 13	2.2K	2.2k	Potentiometer	trimmer at Q4 collector, value unknown; read from the schematic by eye
Attack	A10K	A10k	Potentiometer	10K log; read from the schematic by eye
Volume	A1K	A1k	Potentiometer	1K log; read from the schematic by eye
Switches 2
Drive	DPDT	DPDT		slide switch; read from the schematic by eye
Edge	DPDT	DPDT		slide switch; read from the schematic by eye