Troubleshooting -Stage; Factory Repair; Before You Start; Isolating A Problem - Vulcan-Hart A-130 Service Manual

SECTION - TROUBLESHOOTING - -STAGE

. FACTORY REPAIR

DENTSPLY Ceramco maintains a factory repair
department for those customers not possessing the
necessary personnel or test equipment to maintain the
VULCAN. If a unit is returned to the factory for
calibration or repair, a detailed description of the
specific problem should be attached to minimize
turnaround time. Call factory for PR number before
shipping at 1-800-835-6639.

. BEFORE YOU START

Since no troubleshooting guide can possibly cover all
the potential problems, the aim of this guide is to give a
methodology which, if applied consistently, will lead to
the problem area. Therefore , it is necessary to
familiarize yourself with the VULCAN by reviewing the
functional description and the detailed circuit
description (Section 4) in conjunction with the
schematics (Section 5). Successful troubleshooting
depends upon understanding the circuit operation
within each functional block as well as the block
relationships.
WARNING
With covers removed, dangerous voltage points may be
exposed. Contact with any of these points could cause
serious injury.
The intent of this section is to provide the information to
return the VULCAN to proper operation. Information is
divided into two parts. Part one contains the overall
furnace troubleshooting block diagram which is useful
in isolating defective blocks within the furnace. Part two
consists of a series of circuit guides , one for each block
shown in the block diagram, that provides settings and
measurements for troubleshooting an individual block.
Also, each circuit guide references related schematics
and circuit descriptions. Inspect the components,
wiring and circuit boards of the VULCAN for damage.
Finally, ensure that the fuses are intact and the internal
power supplies are good.

. . ISOLATING A PROBLEM

To successfully troubleshoot this furnace, the symptoms
must first be identified, the faulty block isolated, then
analyzed, and finally the defective component located
and replaced.
After the block is isolated, refer to the appropriate
functional circuit guide.
The circuit guide provides some but not necessarily all
of the possible failure modes for a particular circuit.
Where applicable, a furnace setup procedure is given to
help isolate the problem for a particular failure mode.

. TROUBLESHOOTING GUIDES

. . POWER SUPPLY

To determine a faulty power supply use the table on
page 5-3. To troubleshoot a faulty power supply use the
procedures listed on page 5-4. If the desired results are
obtained in each of the steps in the tables, replace D43,
U9 or U7 as appropriate.

. . MICROPROCESSOR

Generally, when the furnace is totally nonfunctional,
i.e., display is unintelligible, no display, random relay
clicking, no key response, or the front panel LED's stay
on at power up, the problem is in the microprocessor
section. However, before troubleshooting this section,
check the appropriate dedicated circuits for correct
operation. Detailed reading of the circuit description is
also very important. See page 5-5 to troubleshoot the
microprocessor.

. . PERIPHERAL DRIVE

The peripheral driver U6 is accessed at every line
voltage zero crossing by the microprocessor. The logic
state of the eight output drivers, Y0 -Y7, is latched into
the shift register at time t0 on the high to low transition
of SIOE. Input data present at the SI input is clocked
into the shift register on the high to low transition of
SCLK. See page 5-6 to troubleshoot the peripheral
driver.
. . MOTOR DRIVE (OPTIONAL ACCESSORY)
The motor driver U8 is accessed by the microprocessor
to lift or lower the door. U8 provides a feedback to the
microprocessor to indicate an overcurrent condition
which is set at approximately 1.00Amp by resistor R3.
See page 5-6 to troubleshoot the motor driver.

. . ANALOG CIRCUITRY

The reference voltages used to control temperature and
compare voltage signals are derived from the output of
U1-7 (+5V) and D1. See schematics for troubleshooting
individual components. See page 5-6 to troubleshoot
the analog circuitry.

. . DISPLAY BOARD

Serial data present on the input of U1-14 and U2-2 is
transfered to the shift register on the logic "0" to logic
"1" transition of the Clock input pulse. Information
present at any register of U1 is transferred to its
respective latch when the Strobe is high (U1-7). A serial
to parallel conversion takes place. As long as the Strobe
is held high ("1") the latches will accept new data. The
LCD display module will accept valid data on D0 - D7
when the Enable (J1-6) goes from a high to low
transition. See page 5-7 to troubleshoot the display
circuit board.
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