Summary of Contents for CBS AUDIMAX III
- Page 2 ® AUDIMAX ® AUDIMAX III S Automatic level control OPERATING AND MAINTENANCE INSTRUCTIONS May, 1967 Transcribed July 2011 By Robert W. Meister WA1MIK New Figures September 2011 Reorganized October 2011...
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Page 3: Table Of Contents
CIRCUIT BOARD INTERCONNECTIONS SECTION VI - PARTS LIST AUDIMAX III STEREOPHONIC ADAPTER ILLUSTRATIONS FRONTISPIECE AUDIMAX III BLOCK DIAGRAM FUNCTIONAL DIAGRAM STEREOPHONIC ADAPTER SCHEMATIC DIAGRAM AUDIMAX III S/N 101 THROUGH 200, SCHEMATIC DIAGRAM AUDIMAX III S/N 201 AND ABOVE, SCHEMATIC DIAGRAM... -
Page 5: Section I - Introduction
WARRANTY A warranty, with a return post card is included with your Audimax III. Fill out the post card and return it to CBS Laboratories as soon as possible to validate your warranty. FACTORY SERVICE AND REPAIR If you should experience difficulty in installing, operating, or repairing Audimax III, please contact CBS Laboratories, Professional Products, Stamford, Connecticut (Area Code 203) 327-2000. -
Page 6: Specifications
Power Requirements 30 watts at 115/230 volts ac, 50-60 Hz NOTE: As delivered, Audimax III contains a 20 dB fixed attenuator in the input circuit. Removal of this pad will permit user to realize specified maximum gain and minimum input level. -
Page 7: Section Ii - Installation Procedures
If future transportation of the unit is anticipated, save the shipping carton for reuse. PHYSICAL INSTALLATION Audimax III is designed to be mounted in a standard 19-inch-wide rack. The unit requires 3-1/2- inch-high front panel space and is slightly less than 10 inches deep. Install the unit in a reasonably well-ventilated position making certain that there is no high heat producing equipment beneath it. -
Page 8: Section Iii - Setup Procedure
Audimax III input. The oscillator output (at 1 kHz) should be adjusted so as to result in a level 4 dB higher than the normal vu level of the line in which Audimax III is connected. The INPUT LEVEL control is then adjusted for the "0 dB" reading. When an oscillator is connected directly to the Audimax III, it is important that proper impedance matching be observed and that no other loads are present on the line. -
Page 9: Function Switch
GGS threshold is performed.) FUNCTION SWITCH Audimax III is in operation performing automatic level control when the FUNCTION switch is at NORMAL position. Turning the switch to the TEST position causes the gain to hold constant at the same level as for normal operation. The function of the TEST position is to provide for overall system performance measurements. -
Page 10: Stereophonic Operation
The adapter employs resistive mixing of the left and right Audimax III output signals and controls each of the two Audimax IIIS with a signal proportional to the sum of left plus right. In this way, gain changes in both channels are identical, thus preserving the stereophonic perspective, as well as making the system responsive to the true volume level. -
Page 11: Section Iv - Theory Of Operation
The attack time of Audimax III, i.e., the time required to effect a gain reduction when the signal level rises suddenly, is approximately 12 milliseconds and is dictated by the charge-up time of the rectifier 1 capacitor, The recovery time, i.e., the time required to effect a gain increase when... -
Page 13: Circuit Operation
Referring now to the lower right quadrant of Figure 4.2, below an input of -24 dBm (with R8 fully clockwise) Audimax III has a constant gain of 30 dB. This is represented by section OA of the input-output curve. As the input is increased from -24 dBm to -16 dBm, the gain is maintained constant because, although rectifier 2 has developed about -8 volts, rectifier 1 output is zero, and being less negative than rectifier 2, therefore controls the gain. -
Page 15: Gated Gain Stabilization
GATED GAIN STABILIZATION To prevent Audimax III from seeking its maximum gain due to a lapse of audio greater than two seconds, such as occurs in TV and motion pictures, Gated Gain Stabilization is employed. In the discussion to follow, the term "lapse of audio"... -
Page 16: Stereophonic Adapter
Audimax III. STEREOPHONIC ADAPTER Figure 4.3 is a schematic diagram of the Audimax III Stereophonic Adapter circuitry. This board is mounted, together with the MODE switch, in the left (upper) channel unit of two essentially identical Audimax IIIS for use in stereophonic operation. - Page 18 Figure 4.4-a. Audimax III Schematic Diagram s/n 101-200...
- Page 19 Figure 4.4-b. Audimax III Schematic Diagram s/n 101-200...
- Page 20 Figure 4.5-a. Audimax III Schematic Diagram s/n 201 and up...
- Page 21 Figure 4.5-b. Audimax III Schematic Diagram s/n 201 and up...
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Page 22: Section V - Maintenance
Troubleshooting for any apparent malfunction of the Audimax III should begin with a check of the power supply. The Audimax III is designed for operation with a 600-ohm load. A standard 620-ohm resistor may be used during bench check. DC voltages, as measured with a multi- meter rated at 20,000 ohms per volt or greater, should fall between the upper and lower limits as shown on the schematic diagram. -
Page 23: Servicing The Gated Gain Stabilizer
VTVM of 10 megohms or greater input impedance. With no input signal applied to Audimax III, -2 volts dc should be present at point F of the GGS printed circuit board. Monitor this point and feed a 1 kHz signal at -28 dBm with the INPUT LEVEL control R8, fully clockwise. -
Page 24: Transient Performance
+10 dB reading of the GAIN meter. Remove short. R68 can then be set by feeding -6 dBm at 1 kHz to Audimax III, with the INPUT LEVEL control R8 fully clockwise, and adjusting for a 0 dB reading on the GAIN meter. If meter will not go full scale with R72, replace 8056 nuvistor. -
Page 25: Circuit Board Interconnections
CIRCUIT BOARD INTERCONNECTIONS This table was NOT in the original manual; the transcriber added it by examining the schematic diagrams. The modules are probably arranged left to right, looking in from the front. Input Output Logic Signal Name/Function -12VDC -11.7VDC +19VDC +20VDC GR Control... -
Page 26: Section Vi - Parts List
SECTION VI PARTS LISTS NOTE: Resistors are 1/2 watt, 5% unless otherwise indicated. Manufacturer's part numbers and all CBS-specific part and assembly numbers have been omitted from these lists, although they are present in the original 1967 manual. AUDIMAX III... - Page 27 Reference Symbol Component Description Revision Notes Silicon Rectifier 250mA 100PIV Silicon Rectifier 250mA 100PIV Silizon Zener 1N963B 12V 0.4W 5% Silicon Zener 1N968B, 20V 0.4W 5% Silicon Diode 1N456A Matched to within 20% Silicon Diode 1N456A Matched to within 20% CR11 Silicon Diode 1N456A CR12...
- Page 28 Reference Symbol Component Description Revision Notes 2N696 Transistor 2N696 Transistor 2N1374 Transistor 2N1374 Transistor 2N1374 Transistor 2N1374 Transistor 2N1374 Transistor 2N1374 Transistor 5.6 ohm 2w wire-wound 68 ohm 680 ohm s/n > 200: 510 ohms 47 ohm 560 ohm 68 ohm 100 ohm 600 ohm T-pad (150 ohm T-pad optional) 470 ohm...
- Page 29 Reference Symbol Component Description Revision Notes 10 K 5.6 K 24 K 1.5 K s/n < 201: omitted 18 K 180 ohm 180 ohm 18 K 150 K 39 K Pot 10 K 1/6W 20% 39 K 150 K 24 ohm 20 ohm 20 ohm 600 ohm T-pad (150 ohm T-pad optional)
- Page 30 Reference Symbol Component Description Revision Notes 68 K 100 K 6.2 K 1.5 K 100 K 100 K 390 K Pot 1 K 1/6W 20% 3.9 K 1.2 K s/n < 201: 2.4 K 1.5 K Pot 250 ohm 1/6W 20% 560 ohm s/n <...
- Page 31 Reference Symbol Component Description Revision Notes Switch SPST (Test) Power Transformer Input Transformer Output Transformer TB-1 Barrier Strip (5 Term) 8056 Nuvistor tube...
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Page 32: Stereophonic Adapter
STEREOPHONIC ADAPTER Reference Symbol Component Description Mylar 0.1uF 100V 10% Mylar 0.1uF 100V 10% Mylar 0.1uF 100V 10% Mylar 0.1uF 100V 10% DB9P male chassis-mount DB9P male chassis-mount 2N696 Transistor 2N696 Transistor 120 K 120 K 120 K 120 K 4.7 K 4.7 K 68 K...