2.20 New Case Bracket Insulator(s) ............7 2.30 Transformer Insulators..............8 3.00 Troubleshooting..................9 4.00 A4 Service Parts List ................. 10 4.10 A8 Service Parts List ..............13 5.00 Service Manual History ................16 INDEX ....................... 17 Alesis A4/A8 Service Manual------ 03/07/03...
R2 and R3, R4. These are provided so an outboard impedance may be connected to modify the gain and overload characteristics as well as its frequency response. Following the amplifier is a passive low pass (R7, C1) filter that begins to limit the high frequency gain of the amplifier. Alesis A4/A8 Amplifiers Service Manual------ 03/07/03...
This is due to the loss of loop gain when the transconductance stage is required to deliver large amounts of current to the output stage drivers. CR1 and CR2 are connected as clamps to the discrete Alesis A4/A8 Amplifiers Service Manual------ 03/07/03...
V be with temperature can be realized. This tracks the needs of the output stage better. The 5k pot in the bias circuit adjusts the potential of the regulator. A 1.5k resistor (R55) sets the current Alesis A4/A8 Amplifiers Service Manual------ 03/07/03...
If the heat sink gets hotter than 55 deg.C. then an additional 20 resistor is switched in to deliver more current to the fan. The fan Alesis A4/A8 Amplifiers Service Manual------ 03/07/03...
Do not use just a hex nut, as it will probably not be able to hold the clamp pressure any more then the heat sink did. See diagram on next page. Alesis A4/A8 Amplifiers Service Manual------ 03/07/03...
Page 8
Alesis A4/A8 Amplifiers Service Manual------ 03/07/03...
Figures 3 and 4 show the new and old styles of insulator (New style Alesis Part # 5-04-1018). Replace the old insulators and reassemble the brackets and rectifier. Route the wires around the transformer bracket(s) as shown in Figure 5.
The part numbers for the foam insulators are 9-23-1067 for the A8, and 9-23-1068 for the A4. Figure 6-Location For Foam Pads On Casetop Inside All trademarks are property of their respective companies. Alesis A4/A8 Amplifiers Service Manual------ 03/07/03...
J1 or J14 loose. Reseat cable and apply hot glue to prevent re loosening. One channel out. Poor solder connections at Troubleshoot and repair as the Neutrik connector or the necessary. high pass capacitors (see section 1.20). Alesis A4/A8 Amplifiers Service Manual------ 03/07/03...
MAIN GNDCT Group Part.Number Description Ref.Designator Comment 2-99-0031 IC TIP31A NPN (FF) Q 39 2-99-5532 IC NE5532AN DUAL OPAMP (FF) MAIN U 1-3 2-99-7815 REG MCT7815CT +15V TO220 (MOT) 9-23-1068 FOAM PAD TRANSFORMER A4 Alesis A4/A8 Amplifiers Service Manual------ 03/07/03...
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