Logitek BRIGHT-VU Installation and operating instructions

BRIGHT-VU
LED Audio
Level Display
O
p
eration & Service Manual
Bright-VU
-35 -30 -25 -20 -15 -10 -7 -5 -3 -2 -1 0+1 +2 +3 +6 +9 +12 +15
-35 -30 -25 -20 -15 -10 -7 -5 -3 -2 -1 0+1 +2 +3 +6 +9 +12 +15
+18
+18
-35 -30 -25 -20 -15 -10 -7 -5 -3 -2 -1 0+1 +2 +3 +6 +9 +12 +15
-35 -30 -25 -20 -15 -10 -7 -5 -3 -2 -1 0+1 +2 +3 +6 +9 +12 +15
+18
+18
Logitek

All information contained herein is confidential. No portions of this manual may be
reproduced by any means without written permission from Logitek Electronic Sys-
tems, Inc.
COPYRIGHT 1995, LOGITEK ELECTRONIC SYSTEMS, INC.
Logitek Software License Agreement
The Bright-VU unit you have purchased contains embedded software.
ThesoftwareisownedbyLogitekElectronicSystems,Inc.andisprotected
by United States copyright laws and international treaty provisions.
Logitek grants to you the right to use one copy of the embedded soft-
warein eachBright-VUmeteryoupurchase.Youmaynot rent orlease the
software. You may not reverse engineer, decompile, disassemble, or cre-
ate derivative works from the software. You may not create copies of the
software.
ThisstatementwillbegovernedbythelawsoftheStateofTexas,U.S.A.
Logitek reserves all rights not specifically granted in this statement.

Table of Contents
SECTION 1 — GENERAL INFORMATION
1-1 General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1-2 Electrical Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1-3 Instrument Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1-4 Where to find help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
SECTION 2 — PREPARATION FOR USE
2-1 Initial Inspection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2-2 Claims . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2-3 Repacking for Shipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2-4 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2-5 Connecting Mains Power. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2-6 Input Selection on Dual Input Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2-7 Connecting Digital Input Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2-8 Connecting Analog Input Models. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2-9 Alarm Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
SECTION 3 — OPERATING INSTRUCTIONS
3-1 Bargraph Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3-2 Display Ballistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3-3 Using Alignment Tones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3-4 User Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3-5 Resetting the Program. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
SECTION 4 — SERVICING
4-1 General Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4-2 Fuse. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4-3 Handling of CMOS Integrated Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4-4 Access to Circuit Cards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4-5 DSP Control Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4-6 Analog Input Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4-7 Digital Input Card. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4-8 LED Display Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4-9 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4-10 ADC Input Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
SECTION 5 — REPLACEMENT PARTS LIST
5-1 DSP Control Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5-2 Analog Input Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5-3 Digital Input Card. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5-4 LED Display Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5-5 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5-6 ADC Input Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
SECTION 6 — MANUFACTURERS LIST
SECTION 7 — DIAGRAMS
Bright-VU LED Meter
INSTRUCTION MANUAL

SECTION 1 — GENERAL INFORMATION
1-1 General Description
The Logitek Bright-VU is a bargraph type audio
level meter featuring two LED bargraphs. Average
level is always shown and is displayed as a solid bar.
PPM is displayed as a single dot. The meters accept
either analog audio or serial digital inputs and are
available in three 19 inch rack mount configurations,
all with internal power supplies.
1-2 Electrical Specifications
Bargraphs per meter: Two
Indicators per bargraph: 20
Scale Range: -35 dB to +18 dB
0 dB Reference Point:
Analog Input adjustable -20 to +10 dBu
Digital Input -19 dB full scale
Response Time:
VU Mode 300 mSec / 20 dB attack
300 mSec / 20dB release
PPM Mode 0 mSec attack
2.8 Sec / 24 dB release
Frequency Response: +−.1dB (20 - 20K hz)
Analog Input:
Sensitivity -10 to +20 dBU for full scale
rear panel adjustable
Overload Level +24 dBm
Impedance 40K Ohm balanced
20K Ohm unbalanced
CMRR -80 dBu
Connector Female 3-pin XLR
Digital Input:
Codes AES/EBU, S/PDIF
Impedance 110 Ohm balanced
75 Ohm unbalanced
Loop-through 2200 Ohm balanced
Termination transformer balanced
Connector Female 3-pin XLR (IN)
Male 3-pin XLR (OUT)
AC Line Input Voltage:
50-60 Hz 105-129 VAC or
(switch settable) 220-240 VAC
Power Requirement:
BV2-(all) & BDT-(all) 5 watts
BV4-(all) 10 watts
BV6-(all) 15 watts
Dimensions:
1RU enclosure 19"W x 7"D x 1 34“H
Desktop case 6” W x 6 ¼”D x 2 ½”H
1-3 Instrument Identification
The Bright-VU is identified by a model number and
a three or four digit serial number.The model number
andserialnumberappearonalabelonthebackof the
unit near the power cord. All correspondence to your
Logitek dealer or to the Logitek factory should refer to
the model number and serial number.
1-4 Where to find help
Logitek customer service personnel are available
tohelpwithanyquestions,commentsorproblemsyou
might have with the Bright-VU meter, both during and
after the warranty period. Our hours of operation are
8AMto5PMcentraltime.Wemaybecontactedinone
of the following ways:
By Phone: [phone] (U.S.A. & Canada)
or 713-664-4470
By Fax: [phone]
By E-mail: [e-mail]
By Mail: Logitek Electronic Systems, Inc.
5622 Edgemoor Drive
Houston, TX 77081
USA
Page 4 ** Bright-VU Instruction Manual **

SECTION 2 — PREPARATION FOR USE
2-1 Initial Inspection
Check the shipping carton carefully for external
damage. If the carton shows evidence of abuse, ask
the carrier’s agent to be present when the unit is un-
packed. Carefully unpack the unit to avoid damaging
the equipment through the use of careless proce-
dures.Inspect all equipment for damage immediately
after unpacking. Bent and broken parts, dents, and
scratchesshouldbenoted.Ifdamageisfound,referto
paragraph 2-2 for recommended claim procedures.
Keep all packing material for possible future use.
2-2 Claims
If the unit has been damaged, notify the carrier im-
mediately.File a claim with the carrier and advise Lo-
gitek of such action to arrange for repair or
replacement without waiting for a claim to be settled
with the carrier.
2-3 Repacking for Shipment
If the unit must be returned to Logitek, attach a let-
ter to it showing the owner’s name and address.A de-
scription of the necessary service should be included
in the letter.The original shipping carton and packag-
ing materials should be used for reshipment if possi-
ble.Use FRAGILE labels on each surface.Return the
unitfreightprepaid.Besuretoinsuretheunitforitsfull
value.The unit will be repaired promptly and returned
freight prepaid.
2-4 Installation
TheBright-VU models aredesignedtobe mounted
in a standard 19" equipment rack by using the four
mounting holes in the corners of the front panel.Plas-
tic washers should be used to keep the mounting
screws from marring the front panel finish.
Whileflow-throughventilationisnot necessary, the
unitsshouldnotbemounteddirectlyaboveequipment
which produces significant heat, such as equipment
using vacuum tubes. The unit should never be oper-
atediftheambienttemperatureisabove55degreesC
(131 degrees F).
2-5 Connecting Mains Power
Connect the meter to the power mains with the en-
closed power cord. The unit is factory set for 115VAC
operationbut 230VACoperationcan be selected via a
slide switch located next to the power transformer in-
side the unit. To gain access to the voltage select
switch, remove the enclosure top cover.The switch is
located adjacent to the large power transformer. The
mainsconnectorisan IEC standard powerentry mod-
ule and may be used with any IEC type power cord of
15 amps or less.
2-6 Input Selection on Dual Input Models
If the digital receiver can lock onto an input signal
then the meter will display that signal whether it con-
tainserrorsornot.If no signalisconnectedtothedigi-
talinput orthedata rateis outofthereceiver’scapture
range, then the meter will display the analog signal.
This happens even if nothing is connected to the ana-
log inputs.
2-7 Connecting Digital Input Models
The Bright-VU accepts AES/EBU or S/PDIF serial
data at sample rates of 30,000 to 50,000 samples per
second via a female XLR connector on the rear panel.
The input is also wired directly to the male XLR con-
nectoronthebackpanelforuseinloop-throughmode.
The loop-through connector provides a convenient
way to daisy-chain several pieces of equipment off of
one digital output. Loop-through works well with
AES/EBU signals but should be limited to 10 feet with
S/PDIF signals and cables.
S/PDIF signals using RCA type plugs may be con-
nected to the input using an RCA to XLR adapter.
CoaxcablesusingBNCconnectorscan beconnected
tothe inputusingaBNCtoXLRadapter.Both ofthese
are available from Logitek.
AES/EBU Connection
Pin 1: Shield
Pin 2: Signal +
Pin 3: Signal -
Pin-1 and the shell of each XLR is attached directly
to the chassis at the connector.These shielding com-
ponents do not share a ground path with any of the in-
ternal circuitry. One-end-only shield connections are
NOT recommended when using digital input models.
Itisalsoimportanttosetthetwoinputloadswitches
located between the two XLR connectors.
Sw1 Sw2 Ohms Use
Up Up 2200 Loop-through mode
Up Dn 110 Balanced twisted pair (XLR)
Dn Up 75 Unbalanced coax (RCA & BNC)
Dn Dn 44 do NOT use this setting
The Bright-VU is set so that full scale (maximum
code) will light the top bargraph LED (+18 dB).
** Bright-VU Instruction Manual ** Page 5

2-8 Connecting Analog Input Models
The Bright-VU accepts balanced or unbalanced in-
puts via rear panel XLR connectors on analog input
onlymodelsor3-circuit1/4"phoneplugsondualinput
models.The connectors are wired as follows:
Balanced Connection
Pin 1 or Sleeve Shield
Pin 2 or Tip Signal +
Pin 3 or Ring Signal -
Unbalanced Connection
Pin 1 or Sleeve Shield
Pin 2 or Tip Center Hot
Pin 3 or Ring Connect to pin 1
The Bright-VU shield pins are bonded directly to
the chassis at the connector and do not share any
groundpathswiththeinternalcircuitry.Thisallowsca-
bleshieldstobeconnectedatbothendswithoutcaus-
ing hum problems.
The zero reference level for each input can be set
anywhere between -10 dBu and +20 dBu by adjusting
the multiturn gain control located adjacent to each in-
put connector. A small flat blade screwdriver is
needed to adjust the gain.
2-9 Alarm Output
Bright-VU units ordered with the alarm option have
a SPST relay closure that can be triggered by several
selectable fault conditions. The relay contacts are
brought out on the rear panel terminal block.
Thealarmfunctioniscontrolledbyaneightposition
DIP switch located on the DSP control card inside the
enclosure.To gain access to the DIP switch you must
removethe metercoverplate.The followingtablesde-
scribe the alarm parameters available.
Alarm Control
Sw7 Function
Off Alarm output OFF
On Alarm output ON
Too Low Alarm
Sw1 Sw2 Function
Off Off -20 dB below 0 dB
Off On -30 dB below 0 dB
On Off -35 dB below 0 dB
On On -45 dB below 0 dB
Too High Alarm
Sw3 Sw4 Function
Off Off +3 dB above 0 dB
Off On +6 dB above 0 dB
On Off +9 dB above 0 dB
On On +12 dB above 0 dB
Alarm Activation Delay
Sw5 Sw6 Function
Off Off 30 Seconds of continuous fault
Off On 60 Seconds of continuous fault
On Off 120 Seconds of continuous fault
On On 300 Seconds of continuous fault
Peak Display Control
Sw8 Function
Off Peak Dot OFF
On Peak Dot ON
The alarm output is available on the rear panel DIN
connector. All alarms within a single unit share the
same relay. Wire a 5-pin male DIN connector as fol-
lows:
Page 6 ** Bright-VU Instruction Manual **
Male DIN solder side
Relay - Relay +

SECTION 3 — OPERATING INSTRUCTIONS
3-1 Bargraph Description
The Bright-VU meter display contains two multi-
LED bargraph displays mounted one above the other.
The top bar shows left channel and the bottom bar
showsrightchannel.The20segmentsarearrangedin
four color groups. The -35 to -1 dB segments are
green, the 0 dB segment is yellow, the +1 to +3 seg-
ments are orange and the +6 to +18 dB segments are
red. Average (VU) levels are shown as a solid bar
while peak (PPM) levels are shown as a single dot.
3-2 Display Ballistics
In the PPM mode, the display has essentially 0 at-
tack time and a 2.8 second per 24 dB release time.In
average mode, the display has an attack and release
time of approximately 300 milliseconds per 20 dB.
These ballistics conform the international standards
withtheexceptionthat the Bright-VU peak attacktime
is slightly faster.
3-3 Using Alignment Tones
The Bright-VU always displays the actual meas-
ured values of the input signal.If a constant level sine
waveisappliedtothemeter,thePPMdotwillbeabout
3dBabovetheVUbar.Thisisduetothedifferencebe-
tweenthe average and peak valueof a sine wave.The
sizeof the VU to PPM differenceis a function of signal
wave shape and the only signal that has the same VU
and PPM reading is a square wave.
3-4 User Maintenance
Thechassisanddisplaywindowsoftheunitmaybe
cleaned using a mild detergent or isopropyl alcohol
anda softcloth.Do
NOT useabrasivecleanersoraro-
matic solvents to clean the Bright-VU meter units.
**********WARNING*********
The inside of the Bright-VU contains no controls or
user serviceable parts. The cover should only be re-
moved by competent technical personnel capable of
servicing this type of equipment.Hazardous voltages
exist on the underside of some circuit cards.
***************************
Logitek will be happy to provide further information
for servicing the unit. Please contact the factory or
your Logitek dealer for further information.
3-5 Resetting the Program
TheBright-VUcontainssoftwarethatexecutesona
programmableDSPintegratedcircuit.Iftheprocessor
memory becomes corrupted, the meter may function
incorrectly or fail to operate altogether.In most cases,
an independent watchdog circuit will notice that the
meter is working incorrectly and restart the system.
The processor can be reset manually by turning
the power off for fifteen seconds and then back on
again.
** Bright-VU Instruction Manual ** Page 7

SECTION 4 — SERVICING
4-1 General Information
The Bright-VU is designed to need a minimum of
maintenance for long trouble-free operation. Should
repair be necessary, the technician should first read
the information in the manual concerning the circuits
in question and should follow proper procedures for
testing and replacing semiconductors. Logitek engi-
neers are readily available at the factory to provide
technical assistance both during and after the war-
ranty period.
**********WARNING*********
The inside of the Bright-VU contains no controls or
user serviceable parts. The cover should only be re-
moved by competent technical personnel capable of
servicing this type of equipment.Hazardous voltages
exist on the underside of some circuit cards.
***************************
4-2 Fuse
The primary winding of the power transformer is
fused with a 12amp slow-blow 20mm fuse housed in a
fuseholderinaslide-outdrawerunderthepowercord
onthe rearpaneloftheunit.Itshouldonlybe replaced
with fuses of the same type and current rating. The
power cord must be unplugged from the rear panel to
gain access to the fuse holder.
**********WARNING**********
Do NOT replacethefusewithoutfirstdisconnecting
the meter’s power cord from the wall socket, as dan-
gerous voltages are present which may cause electri-
cal shock. Always use fuses of the same value and
type as specified in this manual.Do
NOT use fuses of
ahighervaluethanthosespecified,asashockhazard
and a fire hazard may result.
****************************
A blown fuse is most often, although not always, a
symptom of another failure. Related circuitry should
always be carefully examined after any fuse failure,
especially if a replacement fuse also blows.
4-3 Handling of CMOS Integrated Circuits
All logic components in the Bright-VU meter are
CMOS type integrated circuits. Even though all cir-
cuits have built-in static discharge protection, special
care must be taken in the handling of these devices,
particularly in dry environments.
*******IMPORTANT NOTE********
Do NOT remove or handle CMOS integrated cir-
cuits except in a grounded environment which is free
of the risk of static electricity. Store such circuits on
conductive foam or in anti-static containers. Do
NOT
store on styrofoam or other plastic sheets. Improper
handling may damage these devices.
****************************
4-4 Access to Circuit Cards
The internal components of the meter are ac-
cessed by removing the eight screws that attach the
top cover and removing the cover.
4-5 DSP Control Card
Filtered +9 VDC from power connector P3 is fed to
the+5VDCregulatorIC5viaconnectorP4.+9VDCas
well as -9 VDC from P3 is also passed to the input
cardsviaconnectorsP1andP2.The+5VDCoutputof
IC5isclampedagainstovervoltageandvoltagerever-
sal by zener diode D1.Distributed power is filtered by
C1, C2, C3, C4 and C5.In addition to powering all cir-
cuits on this card, IC5 also supplies +5 VDC to the in-
put and display cards via connectors P1, P2, P5 and
P6.
On power up, the DSP is kept in reset by IC1 until
the power has stabilized, ensuring a good power on
reset.IC1 also contains a watchdog timer that will re-
set the DSP if its ST pin in not taken low at least once
every 150mSec.This pinisnormally pulsedlowevery
5 mSec by a DSP write to address 0.
The DSP (IC4) is clocked by a 12.288 MHZ crystal
oscillator consisting of Y1,C6,C7 and an IC4 internal
driver.IC4, pin43 is a buffered output of the oscillator
andisusedasthemasterclockfortheanalogtodigital
converters on the analog input cards.
The first thing the DSP (IC4) does after reset is
copy its program from EEPROM IC3 to its internal
memory. Note that the 8-bit data bus from the EE-
PROM is connected to the middle byte of the DSP’s
24-bit data port.
AddressdecoderIC2isusedtoresetthewatchdog
timer IC1 and supply the serial bit clock and load sig-
nals to the LED drivers on the display cards.
The front panel PPM/VU slide switches are con-
nected directly to the low byte of the DSP address
port.
Serial data is sent synchronously (data,clock,load)
to the LED driver chips via display connectors P5 and
P6 in 16-bit strings.Data is placed on the top bit of the
DSP data port and clocked into the display drivers via
awritetoaddressdecoderIC2.OtherwritestoIC2will
load the 16-bit strings into the left or right side display
driver.
Page 8 ** Bright-VU Instruction Manual **

Two channel audio data is fed synchronously
(data,clock,frame sync) to serial ports on the DSP via
input connectors P1 and P2.If the control card is only
driving one display then the DSP IC4 will only have
one serial port which will be connected to P1. In this
caseonlyleftsideconnectorsP1andP6willbeactive.
4-6 Analog Input Card
The audio from the left input XLR connector J1 is
connectedtoaRFlowpassfilterformedbyR1,R2,C1
andC2.Theresistorsalsoforma-9dBpadwiththein-
putimpedanceofbalancedreceiver IC1.IC1provides
an additional -6 dB pad between its input and output.
Thesepadsallow+20dBuinput signals tobehandled
bythe+/- 5voltsupplyrails.Signalgainisadjustedvia
trimpot R7 which is the feedback resistor around gain
stage IC3a.
Signal from IC3a is fed through anti-alias filter R9,
C5andDCisolatedbyC8beforeconnectingtothe left
input of the sigma delta analog to digital converter.
Rightchannelconnectstotheconverterviasimilarcir-
cuitry.
The 12.288 MHZ master clock input to the ADC is
generated by a crystal oscillator located on the DSP
control card. Combined left and right audio data is
sent synchronously (data, clock, frame sync) to the
DSP in 64-bit strings via connector P3.
IC5andIC6supplylownoiseregulated+/-5VDCto
theanalogportionsofthecircuit.Thedigitalpartofthe
data converter gets its +5 VDC from the DSP control
card.
4-7 Digital Input Card
Serial digital audio in the AES/EBU or S/PDIF for-
mat enters the card via XLR connector J1 and is di-
rectlyconnectedto theoutputconnectorP2.Notethat
no buffering is applied to the loop through output.
The input data signal is connected to pulse trans-
former T1 via DC blocking capacitor C2.The output of
T1isloadedwithR1,R2orR3,depending on the load
required, and connected to data receiver IC1.C1 and
R4fromaloopfilterusedbyIC1torecovertheembed-
ded clock from the coded input signal.IC1 separates
the audio data, channel data and clock from the input
signal. The audio is sent to the DSP in 64-bit strings
via connector P3.
IC2 creates a low noise +5VDC for use by the ana-
log front end of IC1.The voltage is stabilized by C6 &
C3 and is clamped against over or reverse voltage by
D1.
4-8 LED Display Card
Regulated +5 VDC from J1 is stabilized by C1, C2
and connected to LED display driver IC1.IC1 controls
the40displayLEDsby scanningtheminasixbyeight
matrix.Segment lines are current controlled and con-
nected to the LED anodes. Digit lines connect to the
LED cathodes. Scanning is accomplished by taking
each digit line low one at a time and sourcing current
from the segment lines for whichever of the 8 LEDs in
a digit group need to be lit.
Thedisplay driveraccepts synchronousserial data
(clock, data, load) from the DSP on the control card in
16bitstringscomposedofan addressbyteandadata
byte.About once a second the DSP sends a complete
set of setup codes for the display driver.If the display
card is plugged in while the meter is running, it will re-
main blank for a moment until these codes are re-
ceived.
4-9 Power Supply
Each Bright-VU contains a ground isolated and fil-
teredstep-downpowersupplytocreatethenecessary
operatingvoltages.ThissupplyislocatedonaPCBon
the right side of the meter enclosure.
Mains AC from the power entry module J2 is fed
through fuse F1, located in a drawer under the power
cord in J2, to J1 on supply card LG-253.J1 feeds volt-
age selection switch S1 which connects the dual pri-
maries of transformer T1 in series for 230 VAC
operation or parallel for 115VAC operation. The dual
secondariesofT1arewiredinparallelandloadedwith
a full-wave bridge rectifier RT1.The DC output of RT1
is filtered by capacitors C1 and C2 and fed to the red
and green output pads. The voltage should be be-
tween 8 to 10 VDC with less than .5 volt of ripple.
Analog input models will also have a charge pump
consisting of IC1 and C3 that feeds filter C4 and the
black output pads. The voltage should be -8 to -10
VDC with less than .2 volt of ripple.
Jumpers soldered to the output pads feed power to
one or two DSP control cards.
**********WARNING*********
DangerousvoltagesfromtheACmainsarepresent
on the bottom of the power supply card. Always dis-
connect the AC power cord when servicing this circuit
board. Always completely reinstall this board before
reconnecting the power cord.
***************************
4-10 ADC Input Card
The audio from the left input 1/4" phone connector
J2 is connected to a RF lowpass filter formed by R10,
R11, C3 and C4. The resistors also form a -9 dB pad
withtheinputimpedanceofthebalancedreceiverIC4.
IC4providesanadditional-6dB pad betweenitsinput
andoutput.Thesepadsallow +20dBuinputsignals to
be handled by the +/- 5 volt supply rails.The output of
IC4isunitygaininvertedbyop-ampIC2bandfedback
tothereferenceinput of IC4.This enablesIC4to pres-
ent an identical resistive load on its two input pins.In-
put gain is adjusted via trimpot R9 which is the
feedback resistor around gain stage IC1b.
** Bright-VU Instruction Manual ** Page 9

*********IMPORTANT**********
Only replace IC2 with an op-amp which is slower
than the SSM2143 such as the TL072 used here. A
faster op-amplikethe NE5532 willcausetheoutputof
IC4 to oscillate.
****************************
Signal from IC1b is fed through anti-alias filter R14
C8 and DC isolated by C11 before connecting to the
left input of the sigma delta analog to digital converter
IC7. The right channel connects to the converter via
similar circuitry.
The 12.288 MHZ master clock input to the ADC is
generated by a crystal oscillator located on the DSP
control card. Combined left and right audio data is
sent synchronously (data, clock, frame sync) to the
DSP in 64-bit strings via connector P3.The reset sig-
nal from the DSP control card is also connected to the
ADC. The DSP activates the reset once a day which
causes the ADC to perform a self calibration routine
for about half a second.If the meter has undergone a
substantial temperature change, it may generate
noise up to -70 dBFS until it undergoes a calibration
cycle
Thethreesupply voltagesfromP3areEMI isolated
by ferrite beads FR1,FR2 and FR3 before connecting
to the other circuitry. IC5 and IC6 supply low noise
regulated +/- 5 VDC to the analog portions of the cir-
cuit. The digital part of the data converter gets its +5
VDC from the DSP control card.
Page 10 ** Bright-VU Instruction Manual **