Infinity Intermezzo 3.5c User manual

INTERMEZZO 3.5c
Powered Center Channel
Service Manual
Infinity Systems, Inc
250 Crossways Park Dr.
Woodbury, New York 797
REV 2 3/2002

INTERMEZZO 3.5c
CONTENTS
SPECIFICATIONS …………………………………………………….3
DETAILED SPECIFICATIONS ………………………………………4
CONTROLS and CONNECTIONS ……………………….…………6
TEST SET UP AND PROCEDURE …………………………………8
SERVICE BULLETIN INF2002-3…………………….………………9
IM 3.5c ADJUST BIAS PROCEDURE………………………………10
EXPLODED VIEW of INTERMEZZO 3.5c …………………………11
EXPLODED VIEW of AMPLIFIER …………………………….……12
PACKAGING ……………………………………………………….…13
WIRING DIAGRAM/PASSIVE CROSSOVER NETWORK ………14
ELECTRICAL PARTS LIST ……………………………….…………15
INTEGRATED CIRCUIT DIAGRAMS ………………………………20
PRINTED CIRCUIT BOARD DIAGRAMS………………..…………21
SCHEMATICS …………………………………………………………25

INTERMEZZO 3.5c
3
Specifications
Frequency Response: 80Hz - 20kHz (±1.5dB)
60Hz - 22kHz (±3dB)
Recommended Amplifier Power Range 25-150 watts*
Internal Amplifier Power 250 watts RMS
(with 0.1% THD @ 100Hz)
2nd- and 3rd-Order Harmonic Distortion <1%
(80Hz - 20kHz@95dB SPL)
Sensitivity: 90dB (2.83V @ 1 meter)
Nominal Impedance: 8Ω
Crossover Frequencies: 350Hz; 2800Hz - 24dB/octave
Mid-Bass Transducer: Dual 5-1/4” (133mm) cone - C.M.M.D.,
magnetically shielded, neodymimum
magnets, 7.7 ohms, DCR±10%
Midrange Transducer: 3-1/2” (89mm) cone - C.M.M.D.,
magnetically shielded, neodymimum
magnets, 4.8 ohms, DCR±10%
High-Frequency Transducer: 1” (25mm) dome magnetically shielded
- C.M.M.D., neodymimum magnets,
3.5 ohms, DCR±10%
Dimensions (H x W x D): 8-3/4" x 22" x 8"
(22.2cm x 55.9cm x 320.3cm)
Weight: 27 lb (12.3kg) Each
* The maximum recommended amplifier power rating will ensure proper system headroom to allow
for occasional peaks. We do not recommend sustained operation at these maximum power levels.

Detailed Specifications
INTERMEZZO 3.5c
4

INTERMEZZO 3.5c
5
Detailed Specifications (Cont.)

INTERMEZZO 3.5c
6
Controls and Connections

INTERMEZZO 3.5c
7
Controls and Connections (Cont.)

INTERMEZZO 3.5c
8
SYSTEM AURAL SWEEP TEST
Equipment needed:
Function/signal generator/sweep generator
Integrated Amplifier
Multimeter
Speaker cables
General Unit Function (UUT = Unit Under Test)
1. Remove the loudspeaker grille.
2. Depress the "High-Pass Filter" button on the rear faceplate; switch the TV control to None.
3. Connect one pair of speaker cables to the input terminals on UUT. Cables should be
connected to an integrated amplifier fed by the signal generator.
4. Turn on signal generator and adjust so that speaker level output at the amplifier is 7.0V, 80 Hz.
5. Plug in AC power cord and turn on UUT with the power switch; LED on the Level control
should light - Red initially and Green after step #6 is followed.
6. Turn up the level control on the front of the UUT to "10". (Maximum). Woofers should be
driving close to maximum excursion at this point.
Sweep Function
1. Follow steps 1-6 above, using a sweep generator as a signal source.
2. Sweep generator from 20Hz to 300Hz. Listen to the cabinet and drivers for any rattles, clicks,
buzzes or any other noises. If any unusual noises are heard, remove woofers and test.
Driver Function
1. Remove woofers from cabinet; (See Page 9), detach + and - wire clips.
2. Check DC resistance of woofer; each driver should be 7.7 ohms ±10%
3. Connect a pair of speaker cables to driver terminals. Cables should be connected to an
integrated amplifier fed by a signal generator. Turn on generator and adjust so that speaker
level output is 5.0V.
4. Sweep generator from 20Hz to 1kHz. Listen to driver for any rubbing, buzzing, or other
unusual noises.
Test Set Up and Procedure
SIGNAL
GENERATOR
AMPLIFIER
AC VOLT
METER (10V) INTERMEZZ0 3.5c
UNDER TEST
SPEAKER
OUTPUT
FROM
AMPLIFIER
00314

Service Bulletin
Service Bulletin INF2002-03 - February 2002 Warranty labor rate: MINOR repair
To: All Infinity Service Centers
Model: Intermezzo 3.5c
Subject: No Output
In the event you receive an Intermezzo 3.5c center channel loudspeaker with the complaint: “There is
no output, and the LED on the volume control does not light, red or green”, check the items listed
below:
Check the 3A line fuse to make sure it’s not open. If open, replace with a 3A MDL (.25 x 1.25) slo-blo fuse,
Infinity part# 80126.
Locate R22 in the power supply section, as shown below.
If value of R22 is not 100k ohms ±5%, then replace R22 with a 1/2 Watt 100k ohm ±5%, resistor.
1. Remove the grille. Lay the loudspeaker on its face on a padded surface, amplifier facing upwards.
2. Remove the black metal bottom cover, (10) Phillips screws; remove the (6) Phillips screws on the amplifier
faceplate.
3. Lift the amplifier out of the enclosure cavity; detach connectors when necessary for access.
4. Locate the power supply section and R22 from the illustrations below. R22 can be checked in-circuit and
should be 100k ohms ±5%. If it is any other value, or open, replace with Infinity part# RC0082.
5. Replace the amplifier, bottom cover, and test the loudspeaker.
9

IM 3.5c ADJUST BIAS PROCEDURE
(Mandatory when any output MOSFET transistors Q3,4,7,8 are replaced)
1. Amplifier should be unplugged and OFF.
2. Remove Amp assembly from cabinet, following the instructions on Page 9. All wires can
remain connected unless they will prevent you from removing the amplifier or accessing
potentiometers on the Linear board PCB in the following steps.
3. Locate the Linear board assembly (PCB with the output transistors)
4. Adjust R11 and R27 fully Counter Clockwise. See diagram below.
5. Apply 120 VAC power to unit, Turn power switch ON.
6. Verify LED illuminates on the front gain control dial unless you have disconnected the plug.
7. Remove shorting plug on terminal J7 on Linear board, and insert current meter, set to the
low mA range.
8. Verify initial current is less then 1 mA.
9. Adjust R11 Clockwise until current meter reads 5 mA + the initial current from step #8.
10.Adjust R27 Clockwise until current meter now reads 10 mA + the initial current from step #8.
11.Turn amplifier OFF. Disconnect AC power to unit.
12.Remove current meter; insert shorting plug back in terminal J7.
13.Replace cover (if present), wires if disconnected, and replace amplifier back into cabinet.
10