SECTION 4 — MAINTENANCE
4-1 General Information
The Ultra-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 Ultra-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 1/2 amp slow-blow 20mm fuse housed in
a fuse holder in a slide-out drawer under the power
cord on the rear panel of the unit. It should only be re-
placed 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
replace the fuse without first disconnect-
ing the meter’s power cord from the wall socket, as
dangerous voltages are present which may cause
electrical shock. Always use fuses of the same value
and type as specified in this manual. Do
NOT
use
fuses of a higher value than those specified, as shock
hazard and 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 Ultra-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 * * * * * * * * * *
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 controllers. Do
NOT
store on styrofoam or other plastic sheets. Improper
handling may damage these devices.
* * * * * * * * * * * * * * * * * * * * * * * * * * * * *
4-4 Access to Circuit Cards
Access to the circuitry of the rackmount and half-
rack meters is accomplished by removing the six
screws that attach the top cover. The inside of the
desktop unit is accessed by removing the four screws
along the edges of the bottom panel and pulling apart
the two halves of the plastic case.
4-5 Power Supply LG-253
Each Ultra-VU contains a ground isolated and fil-
tered step-down power supply to create the neces-
sary operating voltages. This supply is located on a
PCB on 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 230VAC
operation or parallel for 115VAC operation. The dual
secondaries of T1 are wired in parallel and loaded
with 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 .1 volt of ripple.
Jumpers soldered to the output pads feed power to
one or two meter control cards.
* * * * * * * * * * WARNING * * * * * * * * * * *
Dangerous voltages are present on the bottom of
the power supply card. Always disconnect the AC
power cord when servicing this circuit board.
* * * * * * * * * * * * * * * * * * * * * * * * * * * * *
4-6 Analog Input Control Card LG-266
+7 VDC from input connector P4 is connected to
voltage regulators IC12 and IC5 as well as display
board connector P6. IC12 feeds the digital section of
the PCB while IC5 feeds the analog front end. -7 VDC
from input connector is connected to voltage regula-
tor IC6 which feeds the analog front end.
On power up, the DSP is kept in reset by IC8 until
the power has stabilized, ensuring a good power on
reset. IC8 also contains a watchdog timer that will re-
set the DSP if its ST pin is not taken low at least once
every 150 mSec. This pin is normally pulsed low
every 5 mSec by the left bargraph load signal.
The DSP (IC11) is clocked by a 12.288 MHz crys-
tal oscillator consisting of Y1, C26, C25 and an inter-
nal driver. IC11, Pin 43 is a buffered output of the
oscillator.
Page 9
** Ultra-VU Operation & Service Manual **
Summary of Contents for ULTRA-VU
Page 1: ...ULTRA VU LED BARGRAPH AUDIO METER Operation Service Manual Logitek...
Page 17: ...SECTION 7 Diagrams Page 17 Ultra VU Operation Service Manual...
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