M405 — Portable Extended Vu Meter

M4o5 PORTABLE EXTENDED RANGE vu METER Refer to Front & Rear Layout B405-04-001 ) vu Meter movement. Standard scale, movement complies to ASA vu Meter standards_ 2 ) Charge Indicator is Iit during battery charging 3) OFF /ON/TEST switch (SW4) activates the instrument in the "ON" position by applying power from either the internal battery pack or from the AC Iine.

In addition the battery condition is measured in the "TEST" position. Sufficient charge is indicated by needle deflection into the red coloured region of the vu meter scale (0 to +3) 150/600 mpedance Switch (Sw2) compensates the meter indicat- ion for voltage present at the input terminals when the instrument is connected to read across 150 or 600 ohm circuit.

For examp le, vu level would normally read dB lower when the instrument was connected to signal developed across 150 ohm transmission Iine than if it was connected across 600 ohm Iine_ By selecting SW2 to the known transmission ine impedance direct scale reading may be obtained without the need for correction factors_ 5 ) 20K/MATCH switch (SW1 ) selects bridging or ma tching input at the input terminals of the M405 _ The bridging mode is for use with terminated transmission lines and where introduction of the meter to the system is required not to load the circuit.

The match ing mode is for use - when the sending Iine is unloaded and, therefore, requires termination to produce the designed system level 6 ) FILTER switch (sw3) inserts 60 Hz narrow band rejection notch within the meter amplifier to minimize the effects of hum present with the signal to be measured_ Thus the possibility of error due to the presence of 60 hz hum component in the circuit is elimated _ 7 ) INPUT binding post terminals_ signal source may either be connected to these terminals or to the telephone type input jack (see 8 ) 4-1

M4o5 PORTABLE EXTENDED RANGE vu METER (Refer Fron Rear Layout B405 04-001 ) vu Meter movement. Standard scale, movement complies vu Meter standards ASA Charge Indicator lit during battery charging. OFF /ON/TEST switch (SW4) activates thc instrument the "ON" position by applying power from either the internal battery pack from the AC line ddition Ine battery condition measured the "TEST" position.

Sufficient charge indicated by needle deflection into the red coloured region the vu meter scale (0 +3) 50/600 Impedance Switch (SW2 ) compensates the ter indicat- ion for voltage present the input terminals wnen the instrument connected read across 150 600 ohm circuit For examp vu level would normally read dB lower when the instrument was connected signal developed across 50 onm transmission Iinc than was connected across 600 ohm Iine_ By selecting Sw2 the known transmission Iine mpedance direct scale reading may be obtained without the need for correction factors 20K /MATCH switch (Swi ects bridging matching input the input terminals the M405 Thc bricging moce for use with terminated transmission Iines and where introcuction the meter the system required not load the circuit The ma tching mode for usC when the sencing Tine unloaded anc therefore, requires termination produce the designed system level FILTER switch (Sw3) inserts Hz narrow band rejection noich thin the meter amplifier minimize the effects hum present with the signa be measured_ Thus the possibility error due the presence hum component the circuit elimated.

INPUT binding post tcrminals connected these terminals jack see 8 ) signal source may either be the telephone type input

M4o5 PORTABLE EXTENDED RANGE vu METER 8 ) An input connected to the meter via the telephone type input jack automatically disconnects the binding post terminals from the input circuit. The M405 input offers floating input to the source. The body of the telephone jack and the ground binding post terminal are connected to the chassis ground of the instrument.

9) headset may be connected via output telephone jack J5 in order to Iisten to the program transmission and to identify the meter indication. In addition, this output source offers the capability of driving 600 ohm Iine to approx mately dBm and hence adapts the MLo5 for booster amplifier applications with visual indication of program transmission. Low level input signals from -50 dBm may be adjusted via the M4o5 amplifier circuit to produce dBm at J5 output_ 10) Calibrated Rotary Attenuator (R3) controls the range of the instrument .

40 steps are provided, with detents, and the pot- entiometer is arranged to attenuate in dB/step increments . The instrument panel is engraved to indicate the correction that is added to the meter indication to obtain the vu level reading for the circuit of interest. Levels from -50 dBm to +30 dBm are accommodated and produce vu reading. 11) AC receptacle.

Connect power cord to recharge battery pack _ 4-2

M405 PORTABLE EXTENDED RANGE vU METER Range 550 dBm to +30 dBm in vu reading. dB steps for Frequency Response: +/-0.25 dB from 20 Hz to 20 kHz . -30 dB down at 60 Hz with filter in. Noise: Signal to noise ratio better than 50 dB measured from vu meter reading_ Total Harmonic Distortion Less than 1% from 20 Hz to 20 kHz (measured with any specified input level and at vuU output level ) Source Impedance 150/600 ohms.

Input mpedance: Selectable, 150/600/20K ohms +/-5%, unbalanced, floating above ground_ Attenuator Tracking +/-0.25 dB per step (non cumulative) Meter Ballistics Complies with ASA vu meter standards. Headset Output: dBm (approx) 600 ohms Power Requirements: Self-contained re-chargeable batteries. Line cord supplied to operate from 115V ac and to re-charge cells . Battery Life: More than 40 hrs continuous use. Typically 30 days at hrs.

per day intermittent use. Dimensions 5.00" wide 9.00" high 5.00" deep (125mm 225mm 125mm) Wei ght: Ibs. (3 kg) net . T-1

M4o5 PORTABLE EXTENDED RANGE vu METER Range 350 dBm to +30 dBm in vu reading_ dB steps for Frequency Response: +/-0.25 dB from 20 Hz to 20 kHz . -30 dB down at 60 Hz with filter in. Noise: Signal to noise ratio better than 50 dB measured from vU meter reading_ Total Harmonic Distortion Less than 1% from 20 Hz to 20 kHz (measured with any specified input level and at vu output level ) Source Impedance: 150/600 ohms_ nput mpedance: Selectable, 150/600/20K ohms +/-59 , unbalanced, floating above ground Attenuator Tracking +/-0.25 dB per step (non cumulative) Meter Ballistics Complies with ASA vu meter standards.

Headset Output: dBm (approx) 600 ohms Power Requirements: Self-contained re-chargeable batteries. Line cord supplied to operate from 115V ac and to re-charge cells . Battery Life: More than 40 hrs continuous use. Typically 30 days at hrs. per day intermittent use. Dimensions 5.00" wide 9.00" high 5.00" deep (125mm 225mm 125mm) _ Wei ght Ibs. (3 kg) net . T-1

RANGE -5Odbm to +30dbm in 2db steps for VU reading FREQUENCY RESPONSE f0 . 25db from 20hz to 20Khz -30db down at 6Ohz filter in NOISE Signal to noise ratio better than 50db measured from VU meter rea ding TOTAL HARMONIC DI STORTION Less than 1% from 2Ohz to 20Khz (measured with any specified input level and at VU output level)

Refer to schematic B405-02-001 The signal input to the M405 Extended Range VU Meter may be via binding-post terminals J2 and J3 or via telephone jack Jl_ An input via Jl automatically disconnects the binding-post input circuit which is completed via the normal springs of the jack _ The input amplifier configuration is unbalanced but floating with respect to chassis ground and can, therefore, be utilized in conjunction with balanced audio lines without introducing disturbances Ma tching/bridging switch, SW1, determines the load presented by the 1 nstrument to the source (Matching or 20K ohm bridging) Meter impedance switch, SW 2 , compensates the input of the instrument to present the proper line termination and simultaneously adjusts the instrument voltage gain to produce the correct meter indication for 150 or 600 ohm line measurements

The M405 is ready for immediate use The re-chargeable, nickel cadmium batteries are installed ini tially pr ior to shipment from the factory and need only be replaced in the event of malfunction due to non-compliance with the speci fied re-charging instructions (Refer to MA INTENANCE section) Prior to operation check the condition of the battery complement. Selector switch SW4 connects the battery circuit to provide meter indication when selected to the BAT .

TEST pos ition. Satisfactory battery condition corresponds to VU meter indication of between and +3VU At full charge the VU meter indicates +3VU and corresponds to battery voltage of 25 volts; 0 VU corresponds to battery voltage of 20 volts and represents the minimun safe discharge limit_ Connecting the ac line cord to the instrument and selecting SW4 to the ON position automa tically places the batteries in the charge mode Indicator neon DS1 is illuminated during the charging operation Approximately 24 hrs is required to restore the battery complement to the fully charged condition Erom the maximum discharge condition 2

section) The VU meter indicates +3VU for the fully charged condition, corresponding to 25 vo]ts battery output The minimum sa fe discharge imit is indicated on the VU meter at Odbm, corresponding to 20 Vo]ts battery output DO Not discharge the batteries completely or permanent dama ge Wi1I result. When the meter indicates 0 VU in the BA T. TEST mode s imply connect the a C Tine cord select SW4 to the on position and Tea Ve overnight Alternati vely , the instrument may be opera ted while in the charge mode and s imultaneous ly receive full charge _ 8

M4o5 PORTABLE EXTENDED RANGE VU_METER The M4o5 designed for dependable, troub e-free service. However Js with all high quality electronic equipment_ regular schedule inspection should be established Any accumulation dust should be periodically removed with soft brush and vacuum hose The active circuitry may be inspected by removing the instrumen: front panel , Remove the two 4-40 screws top and two rubber feet the bottom that secure the front panel the meter case The componen board ma removed for inspection by removing the [wo nuts which secure the PC board the meter terminals this manner ccess may be gained the der side the PC board.

ecessary remove instal batteries, release the battery clamp Disconnect the battery terminal clips and remove batteries Install new units and secure battery amp by re-locating the 4-40 retaining screws The retaining screws tap into the meter side panel fault suspected, measuring the dc voltage present the transistor electrodes may assist determine the cause When compar ing the measurements listed tne voltage char| consideration should given the fact that, for direct coup ed sections, fault one circui may cause abnorma conditions other circuit areas within the same section.

necessary interchange component determine the cause fault, remove the suspected component with small dering iron and desoldering tool Place the soldering iron and the desol dering [ool the solder connection be desol dered When the der melts thoroughly , Press the plunger release trigger any the lead connections stick the printed rcuit board, free them with scribe similar sharply pointed instrumeni_ Carefully remov the component which, proven De satisfactory, may used again for other applications To install the new component, snape the Teads the correct spacing Insert he part and fold the Ieads under the printed circui board firmi hold tne component.

Clip off the excess wire leav {ng about 1/16 inch Solder the new eads using resin core solder and clean the board with an neri fluid such as perch- lorethelyne The Iocation of components shown in drawing B142-06-001 5-1

The M405 is designed for dependable, trouble- free service; however , a5 with all high quality electronic equipment, regular schedi le of inspection should be established. Any accumulation of dust should be periodically removed with soft brush and vacuum hose The active circuitry may be inspected by removing the instrument back plate Disconnect the ac line cord and remove the four 4-40 screws that secure the back plate to the meter case Exercise care when removing the back plate in order to prevent damage to the ac wires connecting from the plate receptacle to the instrument power supply.

The component board may be moved outward for inspection by removing the two nuts which secure the PC board to the meter terminals In thi manner access may be gained to the foil side of the PC board If it is necessary to remove or install batteries, release the battery clamp (black anodized plate secured by two 4-40 screws Disconnect the battery terminal clips and remove batteries Install new units and secure battery clamp by re- locating the 4-40 retaining screws The retaining screws tap into the meter side panel If fault is suspected, measuring the dc voltage present at the transistor electrodes may assist to determine the cause When comparing the measurements listed in the voltage chart consideration should be given to the fact that, for direct coupled sections, fault in one circuit may cause abnormal conditions in other circuit areas within the same section If it is necessary to interchange component to determine the cause of fault, first remove the solder from t he printed circuit foil fillets associated with the suspected defective component To do this, light soldering iron should be used (25 watts) in ombination with an inexpensive vacuum action type hand desoldering tool The desoldering tool is designed for component reworking and comprises teflon tip and cylinder equipped with spring plunger which, when loaded and released, creates high impulsive vacuum to draw the molten solder off from the printed circuit board and into the cylinder

M405 EXTENDED RANGE VU METER PART DESCRIPTIon MFG MFG PART NUMBER H1 Sma 1 1 Knob Grey Cap Elma 023-4520 040-4010 H2 Large Knob Grey CaP Skirt 021-5520 040-5010 042-4920 J1 2 8 3 Jack Bind ing Post Red Binding Post Black Green Jack ADC Johnson PJ-339 DF - 30-RC DF-30-BC DF-30-GNC Pj-339 ADC Jack Mounting Block WBS 4405-03-006 P1 Chassis Receptac 1 e Switch- Craft EAc-301 M1 Vu Meter Bach - Simpson 544-MC PCB Printed Circuit Board WBS M142 Transistor N FET PNP NPN NPN PN P Fa irchild 2N 5163 Motoro ] a 2n 5087 2N 4401 2N 4401 2N 5087 8 Transistor NPN 86 PNP PNP 600 ohm 3-watt RZ 150 o hm 3-watt R3 Att 25k 40 Step 2dB Steps R4 Res istor 1K Yw 5 % R5 1M Motoro ] a 2N 4401 2N 5087 2N 3645 Fairchild Da ] e RS 2B RS 2B RP8606-01- RND Altec Phi]ips

M405 EXTENDED RANGE VU METER PARI DESCRIPTIon MFG MFG PART NUMBER SW1 SW2 SW3 SW4 Switch Togg] e SPST C & K DPDT SPST 3 - po ]e, 3-pos Rotary Centra lab Power Trans former Hammond 7101 7201 7101 PA 2007 T1 # 166c50 XF1 XF2 XF3 XF4 XFS Fuse C]ip Battery C]ip Ma ] e Ma ] e Fema 1e Fema Buss 37001 Cinch Jones #5M #5M #5F #5F W1 Power Cord Be Iden BR 7232 13