M608

M608 AUDIO DISTRIBUTION AMPLIFIER (600 Ohm Operation) Dimensions : 3 . 4 " wide X 3 . 4" high X 13.7" deep (83 mm X 83 mm X 336 mm ) . Weight: 6 . 5 pounds (3 kg ) net. 1-2

M6c8 AUDIC DSTRIBLTICN AMPLIFIER meiz A5 Sisibe:ien Amie" s2 {-Pc8734 47y I7c the 115V ac Hz power line The modular plug unit designed bridge across single audio source ana provides individually isolated, transformer coup ed, 600 ohm outputs Imut The audio input appears pins P2-8 and P2-16 the rear module connector connected the primary T201 which is strapped present input impedance 30 , 000 onms greater the source Tne Input Shield connects P2-7 The secondary T201 connects the 8-116 amplifier card pins ana An overload protection circuit consisting CR4 prevents excessive input levels potentially damaging the amplifier _ R2 R3 and CRI through voltage transients from The audio signal coupled through C4 the pre-amplifier section, consisting and u2 R12 adjusts gain differences between and u2 optimizing input longitudina balance low frequencies.

R9 provides longitudinal balance adjustment for high frequencies. The gain the M608 determined by the setting control R2o1 which controls the feedback around u2 amplifier gain adjustable from +18 dB sensitivity The overall Quteut The preamplifier output signa coup ed through the lower half the output power amplifier, comprising u3, 01 , 02, 03 04 and 05 The second upper half the output power amplifier consists U4 06, 07 08, and 010, The actively balanced audio output appears at pins 8-116 amplifier card.

and the R23 and R4I adjust the amplifier output offset voltages. +/ - 0.5 mV . volts 2-1

M6o8 V6O8A ALD DiSTR BUTION AMPL IFIER 76 Miz: 225 Z7Futra 7l~ss cire:: , in: :he 23 MF{ mounting frame, which may be installed standard EIA 19 inch equipment rack The MF6 frame wili accommodate maximum M6o8 series amplifiers any combination single multiple width modules not exceeding ten single wicth modules. (ne mouniing Trame nas Deen Procured witnou rECeptacies inesc must installed the appropriate module Positions Each M6o8 type amplifier requires [wo type MFR6 recepticles_ Note: Receptacle Pi , (which contains the ac Iine voltage input) inverted This provides mechnical polarization the connectors necessary prevent inadvertent insertion other companion modules which not operate from the ac Iine.

Where ertical rack space permits and the ultimate noise and crosstalk performance desired, recommended that only modules the same type be allocated each individual mounting frame Alternatively possible mix modules different types by exercising extreme care separate cables carrying differ- ent levels and functions. Place all ac-powered units the right the frame, as ewed from the front. Instal isulating rubber sleeves over all ac soldered terminal connections For externa wiring connections including recommended shielding and ground wiring techniques refer Rear Connector Layout drawing 608-04-001 and System Wiring Schematic 608-02-003 To obtain optimum resu ts, use insulated, shielded, twisted pairs for both input and output wiring Cab Tes operating with level differences exceeding 25 dB should be laced separately and dressed apart from each other Keep power wiring away from low level circuits Ground cable shields one end only.

Ground loops must be avoided _ generally recommended good engineering practice that one rack unit space be provided between full frames distribution amplifiers for optimum entilation . 3-1

M6o8_ M6O8A DISTRIBUTION AMPLIFIER kHz, -10 dBm signal with source impedance Apply 600 for the M6o8 and 150 ohms for the M6o8A ) to of ohms the input binding posts of the test jig. module GAIN control (R2o1 ) fully Ccw and Rotate the conf irm an output level of -16 dBm +/- 0.5 dB _ the module GAIN control fully CW and confirm Rotate an output level of +8 dBm +/ - 0.5 dB _ Note: Remember that signal levels for 150 ohm system to be dB lower in level when referred to will appear calibration (eg _ +8 dBm 150 ohms will read as +2 600 ohm dBm on 600 ohm calibrated are voltmeter) _ f) Check the remaining +/ - 0.5 dB .

outputs for +8 dBm output level 6 a) Increase the input signal level to dBm . b ) Set the module GAIN control for an output level of (unity gain) dB c) common mode signal to the input . This can be Apply accomplished by tying the two input leads together which then connected to one of the generator balanced are Terminate this output with 600 or 150 outputs.

ohms depending on module type. The other generator output should be grounded. Change the input frequency to 400 Hz and adjust R12 to obtain common mode rejection of 65 dB or better . Increase the input frequency to 10 kHz and adjust R9 to obtain common mode rejection of 65 dB or better. f) Return the input frequency to LoO Hz and confirm that the level remains below -65 dBm since the control output ranges may overlap slightly Return the input connections to normal and apply dBm, kHz signal to the test jig input .

the module GAIN control for exactly +8 dBm at the Adjust output - b ) Page of

M6o8 / M6o8A DISTR BUTION AMPLIFIER Check frequency response and confirm that the output level remains at +8 dBm +/ 0.25 dB from 20 Hz to 20 kHz . Increase the input level to +8 dBm and adjust the GAIN control for unity gain. b ) Measure the output noise level which should be 80 dB below +8 dBm (-72 dBm absolute) or better over band- width of 20 Hz to 20 kHz _ Decrease the input level to -10 dBm and adjust the GAIN control for +18 dB of gain (+8 dBm output)_ Measure the output noise level which should be 70 dB below +8 dBm (-62 dBm absolute) or better over band- width of 20 Hz to 20 kHz _ 9_ a) With the amplifier set to +18 dB of gain increase the input level to +6 dBm .

b ) Confirm maximum output level of +24 dBm . Measure the supply current at +24 dBm out nominal current of 195 mA _ Confirm Measure total harmonic distortion which should be less than 0 .5% from 30 Hz to 20 kHz at +24 dBm out. 10_ Using dual trace oscilloscope connect one input channel to the test jig input and the other channel to the jig output_ b ) Confirm all of the amplifier outputs are in phase with the input.

11 _ Solder J1 permanently 12 . Check operation of the LED indicators on the front panel (8-117 card) _ a) The Yel low DC LED should iluminate when Ac power is applied and the +/ - 32 volt DC supply voltage is operat- ional Page of

M608 M6OBA DISTR BUT ION AMPLIFIER Reference M6o8/M6O8A Manuals _ and the 8-116 printed circuit card for Inspect the chassis correct assembly 2 _ a) Insert module into WBS M6o8/A TEST JIG. b ) Connect of C28 _ current meter between Tp1 and the positive side JI should be open if not remove the connecting Note: solder Iink and confirm an open circuit using an ohm meter.

c) AC power through variac to 115V Ac while Slowly apply monitoring the supply current. The supply current should increase to 45 mA idling, no signal appl ied) while the voltage at TP1 should rise to +32V DC _ Check DC voltages on the 8-116 PC board (for reference, no signal applied) U1 through U4, Pin -18V (-0.5 to +1.SV) U1 through U4 , pin +18V (-0.5 to +1.SV ) U1 and u2 , pin OV Adjust the DC offset voltage on u3 and u4 using voltmeter as follows: digital a) b adjust R41 for Ov +/ - 0.2 mV at pin 18 .

adjust R23 for Ov 0.2 mV at pin 19_ 5 a) Switch the module selector on the test jig to the M6o8 or M6O8A position according to the module to be tested _ Note: The test jig input and all outputs are internally terminated (M6o8 600 ohms, M6O8A 150 ohms) The test equipment should be balanced, floating from ground, and present bridging load _ b ) Switch the output SELECT to '1 ' ISSUE APRIL/83 Page of