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Kenwood BASIC M1 Current Source Modification 

www.drmaudtioht.com

 

10/9/2008 6:56 PM 

page 5 of 10 

Parts List 

The following table contains a list of parts included in the kit. 
 

ID 

Value 

Part # 

IC17 LM334z 

 

LM334z 

IC18 LM334z 

LM334z 

R17 

150 ohm ¼ watt 5% resistor 

3011151 

R18 

150 ohm ¼ watt 5% resistor 

3011151 

VR3 

500 ohm linear trim pot horizontal – Hex adjust 

3090501 

VR4 

500 ohm linear trim pot horizontal – Hex adjust 

3090501 

WR1 2mm 

allen 

wrench 

9001101 

 

Summary of Contents for Basic M1

Page 1: ...Kenwood BASIC M1 Audio Power Amplifier Current Source Modification www drmaudioht com ...

Page 2: ...ON The power supply in the Kenwood BASIC M1 amplifier generates hazardous voltages that can cause electrical shock The user of this document assumes all responsibility to follow safe practices to prevent shock or injury while making the modifications described in the document This document is the property of Daniel R Mattis and may not be copied reproduced or distributed in part or entirety ...

Page 3: ...l so an active current source with very high impedance is used in most high end amplifiers Looking at the Kenwood Basic M2 schematic we can see that Q3 and the related components are used to implement a current source for the input differential amplifier This modification replaces the 56K current source resistor in the Basic M1 input differential stage with a LM334Z 3 terminal adjustable current s...

Page 4: ...08 6 56 PM page 4 of 10 The V and V leads of the LM334 are formed to have the same spacing as the original 56K resistor The center lead is formed to allow a 150 ohm resistor to connect from the R lead to the V lead This resistor sets the current of the LM334 current source ...

Page 5: ...g table contains a list of parts included in the kit ID Value Part IC17 LM334z LM334z IC18 LM334z LM334z R17 150 ohm watt 5 resistor 3011151 R18 150 ohm watt 5 resistor 3011151 VR3 500 ohm linear trim pot horizontal Hex adjust 3090501 VR4 500 ohm linear trim pot horizontal Hex adjust 3090501 WR1 2mm allen wrench 9001101 ...

Page 6: ... leads as shown in this photo Note that the resistor is connected between the center lead which is pin 2 of the device and pin 3 You can form the leads as you desire just maintain the lead spacing of 400 inches so the devices will fit in the holes in the boards that were originally occupied by R17 and R18 Step 2 Remove R17 and R18 This photo shows the top side of the amplifier pc board assembly wi...

Page 7: ... 9 2008 6 56 PM page 7 of 10 This photo shows the top side of the amplifier pc board assembly with the original current source resistor R18 removed This photo shows the bottom side of the amplifier pc board assembly with the original current source resistor R17 removed ...

Page 8: ...nal current source resistor R18 removed The first two set of photos are intended to assist in location of the resistors R17 and R18 Step 3 Insert the pre assembled LM334Z devices with the 150 ohm resistors in the original location of R17 and R18 This photo shows the top side of the amplifier pc board assembly with the original current source resistor R18 replaced by the LM334Z ...

Page 9: ...MPORTANT Notice that the orientation of the devices is different for the left and right channel This is due to the fact that the pc board layout is mirrored for the left and right channels This becomes evident upon close examination as most of the semiconductors are orientated 180 degrees between the two channels Idle Current Potentiomenters Replace the open frame idle current pots VR3 and VR4 wit...

Page 10: ...nd verify that it is approximately 0 volts There may be a negative or positive voltage present that could be as much as 100 millivolts or more but it should not exceed 200 millivolts Once it is determined that he amplifier is operating correctly connect the speakers and power the amplifier up Allow time for the amplifier to heat up before proceeding After the amplifier has reached operation temper...

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