Global Specialties 1310 - Manual (Page 10)

3.3 PRECAUTIONS :
The Power supply is ideally suited to virtually any type of IC
breadboarding from TTL, CMOS, and ECL to op-amps, audio and
video amps, phase-locked loops, and microprocessor circuitry.
However, certain normal breadboarding precautions should be
taken to avoid ground loops and inadvertent loading. Observance
of correct load polarity is also important, since most ICs may be
damaged by improper power supply connections.
3.4 Polarity :
Observe proper polarity when connecting the power supplies to the
load, especially if the load is polarity sensitive and does not have
reverse polarity protection.
3.5 Ground Loops :
A ground loop is voltage drop on a ground bus caused by a power
stage output entering the ground bus some distance away from the
power supply ground binding post.
This small voltage drop, though only millivolts or microvolts, is part
of the output load. If a preamplifier input or circuit ground is
connected to a portion of this ground bus, feedback and oscillation
may occur. To prevent this, all output stages should be positioned
as close as possible to the ground terminal, with preamps being
father awat. Many audio ICs have separate input and output grounds
to prevent ground loops.
Even though the power supplies are tightly regulated, a short length
of power bus can prevent enough inductance to cause linear IC
oscillation at high frequencies. For this reason, effective bypass
capacitors are needed to bypass the power busses as possible to
the power supply pins of the IC. Disc ceramics ( 0.1µF ) work well
and should be placed across as may ICs as possible. Do not use
electrolytic or paper capacitors because they have high inductances
and cease to act as bypasses above one or two megahertz.
Bypassing is required with digital ICs also; problems such as
inability to reset or to clear and false triggering can occur if bypass
capacitors are not installed.
3.6 Ventillation :
The heat generated in the power supply is convected through the
ventilation slots in the bottom and top of the case. For best ventilation,
always leave a few inches of space around the unit. Never allow any
object to block the ventilation holes or reduce the clearance provided
by the feet on the bottom of the case.
6
SECTION - 6
MAINTENANCE AND CALIBRATION
6.1 FUSE REPLACEMENT :
The 1310 uses a type 3AG, ½A ( ¼A for 230 volt units ), 250 volt slow
acting power fuse. If replacement becomes necessary, follow this
procedure :
a. Disconnect all cables and connections to the 1310.
b. Unplug the power cord at the AC outlet.
c. Unscrew the fuse holder cap from teh fuse holder ( found on the rear
panel ).
d. Remove the defective fuse and replace it with one of an identical type
and rating.
e. Reinstall the fuse holder cap, making sure that it is tightened securely.
If any additional maintenance or repair is require, it is recommended
that the unit be returned to Global Specialties for service ( see FACTORY
SERVICE and REPAIR ).
6.2 CALIBRATION :
The 1310 has been designed to provide years of trouble-free service,
but to maintain the accuracy of the digital display the unit should be
returned to the factory on an annual basis, or whenever the accuracy of
the display is in question. If this is not possible or practical, the following
calibration can be performed in the field :
6.2.1 Equipment Required :
( 1 ) Digital multimeter, 3½ digits or greater, with an accuracy of 0.25% or
better.
( 2 ) 80 Ohms, 5 Watt ( or greater ) resistor.
WARNING : During the course of this procedure, power will be applied
and potentially lethal voltages will be present. Exercise
extreme caution during all phases of the calibration, and
particularly when adjustments are being made.
6.2.2 Procedure :
1 ) Open the case of the 3310, following the procedure outlined under the
CASE DISASSEMBLY section of this manual.
2 ) Apply power to the 3310, allowing at least 15 minutes for warm-up.
3 ) Connect the digital multimeter to pins 35 and 36 of U5' with the positive
lead on pin 35 and the negative lead on pin 35.
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