FirstWatt F5 Turbo V3 User Manual (English)

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F5 Turbo Assembly Instruction Version 2 Page 1

F5 Turbo V3 Assembly Instruction.

1. Introduction:

This PCB is designed base on the Nelson Pass F5T V3 circuit. Details please refer to the article posted by

Nelson on First Watt website: http://www.firstwatt.com/pdf/art_f5_turbo.pdf .

2. Circuit Diagram:

Since the PCB is layout by FETAudio and here is the circuit diagram for reference.

Notes:

a. The Q7 and Q8 is in TO-92 package. I have also put TO-220 package pads in the PCB if the

original transistor recommended by Nelson is used.

b. J7 is a pin header and it should be shorted to ground by a jumper for normal operation. The

“X” point is for those who want to modify the power amp into F5X mode.

c. Since I use Toshiba 2SK1530 and 2SJ201 power mosfets, I have changed some values of

some components and thus please refer to the update BOM (bill of material) for details.

www.FETAudio.com

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FirstWatt F5 Turbo V3 Specifications

General

Brand	FirstWatt
Model	F5 Turbo V3
Category	Computer Hardware
Language	English

Summary

Introduction to F5 Turbo V3

F5 Turbo V3 Circuit Diagram

F5 Turbo V3 Assembly Instruction

Component Soldering Sequence

Details the order for soldering resistors, capacitors, LEDs, VRs, JFETs, and transistors.

JFET and Transistor Soldering

Solder JFETs K170/J74 and transistors Q7/Q8 after initial component soldering.

Varistor and Heat Sink Preparation

Instructions for mounting varistors and preparing the PCB for heatsink attachment.

Mosfet and MUR3020W Mounting

Mount MOSFETs and MUR3020W components onto the heatsink with proper insulation.

Final PCB Securing and Soldering

Secure PCB screws, solder all leads, and mount varistors correctly.

Critical Safety Checks Before Power-Up

F5 Turbo V3 Tuning Procedures

Initial Potentiometer Adjustment and Short Check

Adjust P1/P2 anti-clockwise, check for shorts, and measure resistance.

Output DC Offset Adjustment

Adjust P1 for voltage increase, then P2 to achieve near-zero DC offset.

Bias Current Setting

Set target bias (1A-2A) by measuring voltage across R20/R23, accounting for thermal drift.

Mosfet Matching and Thermal Stability

Verify mosfet matching and ensure stable bias as heat sink temperature stabilizes.

FirstWatt F5 Turbo V3 User Manual