Vulcan®

Furnace

Service Manual

Models:
A-130 3-130 3-550PD
A550 3-550 3-550A
A-1750 3-1750 3-1750A

CERAMCO
®
 SAFETY

SAFETY FIRST
• Don’t bypass the power cord’s ground lead with two-wire extension cords or plug adaptors.

• Don’t disconnect green/yellow safety-earth ground wire that connects the ground lug of the power receptacle to
the chassis ground.

• Don’t plug in the power cord until directed by the installation instructions.

• Don’t repair the furnace unless you are a qualified technician and know how to work with hazardous voltages.

• Don’t locate and operate the furnace in close proximity to combustible materials.

• Observe all WARNING statements. They point out situations that can cause injury or equipment damage.

• Disconnect the power cord before attempting to service.

• It is the user’s responsibility to use only cleaning agents and materials that will not result in hazards to the
equipment or material contained within.

• When replacing the main power supply cord use only a direct equivalent high-temperature cable.

• When replacing the main fuse use only a direct equivalent.

TABLE OF CONTENTS
SECTION 1 5.3.3 Peripheral Drive ........................................5-1
CIRCUIT DESCRIPTION A-CONTROL 5.3.4 Motor Drive ...............................................5-1
5.3.5 Analog Circuitry.........................................5-1
1.1 INTRODUCTION ..........................................1-1 5.3.6 Display Board ...........................................5-1
1.2 CIRCUIT DESCRIPTION ..............................1-1 5.3.7 Fan Drive Control ......................................5-2
1.2.1 Analog Meter Readout ...............................1-1 5.4 TROUBLESHOOTING COMPONENTS............5-2
1.2.2 Front Panel Controls ..................................1-1 5.5 ERROR CODES...........................................5-3
1.2.3 Muffle Control ...........................................1-1 5.6 DIAGNOSTIC TABLES .................................5-4
1.2.4 Power Supply ............................................1-1 5.7 BLOCK DIAGRAM.......................................5-8
5.8 SCHEMATICS ............................................5-9
SECTION 2 5.9 WIRING DIAGRAM ....................................5-12
TROUBLESHOOTING A-CONTROL
SECTION 6
2.1 FACTORY REPAIR........................................2-1 ADJUSTMENT/CALIBRATION3-STAGE
2.2 BEFORE YOU START ...................................2-1
2.3 TROUBLESHOOTING GUIDES ......................2-1 6.1 SCOPE .....................................................6-1
2.3.1 Power Supply ............................................2-1 6.2 FACTORY REPAIR .......................................6-1
2.3.2 Analog Circuitry.........................................2-1 6.3 ADJUSTMENT/CALIBRATION .......................6-1
2.3.3 Triac Drive.................................................2-1 6.3.1 Temperature ............................................6-1
2.4 TROUBLESHOOTING COMPONENTS ............2-1 6.3.2 Door, Lift Drag Adjustment ........................6-1
2.5 BLOCK DIAGRAM.......................................2-3 6.4 CIRCUIT BOARD CALIBRATION ...................6-1
2.6 SCHEMATIC ..............................................2-4 6.4.1 Required Test Equipment ..........................6-1
2.7 CONTROL CIRCUIT BOARD..........................2-5 6.4.2 Temperature .............................................6-1
2.8 WIRING DIAGRAM .....................................2-6
SECTION 7
SECTION 3 SERVICE PARTS
CALIBRATION A-CONTROL
7.1 ORDERING INSTRUCTIONS.........................7-1
3.1 SCOPE ......................................................3-1 7.2 MUFFLE AND THERMOCOUPLE ...................7-1
3.2 FACTORY REPAIR........................................3-1 7.3 MUFFLE (3-550 PD / AIR EXCH)...................7-2
3.3 ADJUSTMENTS...........................................3-1 7.4 CABINET PARTS.........................................7-3
3.3.1 Door, Lift Drag Adjustment ........................3-1 7.5 DOOR PARTS ............................................7-4
3.4 CIRCUIT BOARD CALIBRATION ...................3-1 7.6 A-CONTROLLER PARTS ..............................7-5
3.4.1 Required Test Equipment ..........................3-1 7.7 3-STAGE & 3-550 CONTROLLER PARTS........7-6
3.4.2 Temperature .............................................3-1 7.8 LIFT MECHANISM PARTS (3-550PD) ............7-7

SECTION 4 SECTION 8
CIRCUIT DESCRIPTION 3-STAGE DISASSEMBLY/REASSEMBLY

4.1 INTRODUCTION 8.1 CONTROL DRAWER REMOVAL.....................8-1

4.2 CIRCUIT DESCRIPTION .............................4-1 8.2 TRIAC........................................................8-1
4.2.1 LCD Display Readout.................................4-1 8.3 MEMBRANE SWITCH..................................8-2
4.2.2 Front Panel Control ...................................4-1 8.4 DISPLAY PCB ............................................8-3
4.2.3 Muffle Control...........................................4-1 8.5 A-CONTROL PCB .......................................8-4
4.2.4 Power Supply............................................4-1 8.6 3 STAGE CONTROL PCB .............................8-5
4.2.5 Motor Drive Control ...................................4-1 8.7 DOOR ASSEMBLY/ADJUSTMENT ................8-6
4.2.6 Fan Drive Control ......................................4-1 8.8 HEATING PLATES.......................................8-7
8.9 MUFFLE REPLACEMENT........................ .....8-8
SECTION 5 8.10 THERMOCOUPLE (A-Control) .....................8-9
TROUBLESHOOTING 3-STAGE 8.11 THERMOCOUPLE (3 STAGE) .......................8-9
8.12 MUFFLE REPLACEMENT(3-550 PD)........ ....8-10
5.1 FACTORY REPAIR........................................5-1 8.13 THERMOCOUPLE (3-550PD) ......................8-11
5.2 BEFORE YOU START ...................................5-1 8.14 POWER SWITCH .......................................8-12
5.2.1 Isolating a Problem ...................................5-1 8.15 POWER DOOR REPLACEMENT ...................8-13
5.3 TROUBLESHOOTING GUIDES .....................5-1
5.3.1 Power Supply ............................................5-1
5.3.2 Microprocessor ........................................5-1
 SECTION 1 - CIRCUIT DESCRIPTION - A-CONTROL

1.1 INTRODUCTION To slow down the heatup time of the muffle (RP2 set
clockwise and muffle is at low temperature) a rate
The purpose of this section is to familiarize the user or control potentiometer (RP3) has been added to the
service personnel with the circuit level operation of the circuitry. A sawtooth signal from pin2 of U2 is compared
VULCAN. This knowledge is necessary to aid in trou- with a fixed reference voltage which can be set by RP3.
bleshooting of a unit's failure and may also allow the As the sawtooth voltage exceeds the value of the fixed
user to gain greater insight into the VULCAN’s versatility reference voltage, amplifier U3 produces a negative
for particular applications. A detailed description is output which in turn increases the thermocouple signal
given for the following circuit functions: output from U1 and Vpin3 of U2 and is now more
negative than Vref, thus the triac output pulses stop.
• Analog Meter Readout
• Front Panel Controls 1.2.4 POWER SUPPLY
• Muffle Control The rectified supply current (D2) is zener regulated to
• Power Supply 8.6V and biased by dropping resistors R11, R12.
The positive voltage to U1 and U2 is provided by a 6.8V
zener diode D1.
1.2 CIRCUIT DESCRIPTION
1.2.1 ANALOG METER READOUT
The Type K thermocouple which extends from the back NOTES:
of the muffle is directly connected to an analog meter
which provides the operator with the present muffle ________________________________________________
temperature. The yellow lead of the thermocouple is
connected to the + input of the meter. ________________________________________________

1.2.2 FRONT PANEL CONTROLS ________________________________________________

The power on/off switch provides AC line voltage to the
furnace if the door switch is closed, while the setpoint ________________________________________________
potentiometer (10K) provides the electronics with a
reference voltage which determines the final muffle ________________________________________________
temperature.
________________________________________________
1.2.3 MUFFLE CONTROL
The muffle is controlled by means of a triac. This muffle ________________________________________________
triac may be activated anytime when the AC cycle goes
through zero, and once activated it will only be opened ________________________________________________
again when the AC sine wave passes through 0
volts.The triac is controlled by a Zero Voltage Switch ________________________________________________
(integrated circuit U2) and is configured as a
proportional controller.Trigger pulses are generated ________________________________________________
when the comparator detects Vpin3 is above the Vref.
The sensed temperature from the amplified ________________________________________________
thermocouple signal is then lower than the set value of
RP2. As Vpin3 is near in value of Vref, a proportional ________________________________________________
control takes over, i. e. power is delivered by bursts to
the load. ________________________________________________

________________________________________________

I ________________________________________________

________________________________________________
t

T ________________________________________________

Load Current - Proportional Control ________________________________________________

1–1
 SECTION 2 - TROUBLESHOOTING - A-CONTROL

2.1 FACTORY REPAIR 2.3.3 TRIAC DRIVE

A current pulse from U2 pin 6 of about 60mA will turn
DENTSPLY Ceramco maintains a factory repair on the gate of the muffle triac which in turn will then
department for those customers not possessing the carry the full load current. The voltage across the triac
necessary personnel or test equipment to maintain the is now at 1-2 Vac. In order to comply with norms limiting
VULCAN. If a unit is returned to the factory for the frequency at which a kW size load may be connected
calibration or repair, a detailed description of the to the main line (fluorescent tubes "flickering") a
specific problem should be attached to minimize proportional temperature control is provided by means
turnaround time. Call factory for PR number before of burst firing the triac.
shipping at 1-800-835-6639.
NOTES:
2.2 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 in conjunction with the
schematic. Successful troubleshooting depends upon ________________________________________________
understanding the circuit operation.
________________________________________________
WARNING:
With covers removed, dangerous voltage points may
be exposed. Contact with any of these points could
cause serious injury. 2.4 TROUBLESHOOTING COMPONENTS
2.4.1 DIODE
2.3 TROUBLESHOOTING GUIDES A diode (except a zener) is defective if there is greater
than 1 Vdc (typically 0.7 Vdc) forward voltage across it.
WARNING:
When measuring voltages use battery operated test
2.4.2 OPERATIONAL AMPLIFIER
equipment unless an isolation transformer is
Generally, the “+” and “-” inputs of an operational
connected between circuit input and AC line.
amplifier will have less than 15 mV voltage difference
2.3.1 POWER SUPPLY when operating under normal conditions. If the output
Rectifier diodes D2 and D3 convert the AC line voltage to voltage stays at maximum positive (typically 1/3 of the
a DC voltage, while resistors R11, R12 reduce the current supply voltage), the “+” input voltage should be more
flow thru the 8.6V internal zener diode of U2 and the positive than the “-” input voltage. If the output voltage
6.8V external zener diode D1. Capacitors C1 and C5 filter stays at minimum (typically 1-5 mV), the “-” input
the rectified voltages. Most of the circuit's current voltage should be more positive than the “+” input
consumption is taken up by the triac gate drive. voltage.

2.3.2 ANALOG CIRCUITRY 2.4.3 TRIAC

The thermocouple voltage which ranges from 0-45mV The gate to power line return voltage under load
(25°C - 1100°C) is multiplied by amplifier U1 measures typically 1-2 Vac, while the MT2 to return
approximately 100 times (depending on the setting of voltage measures between 1.3-1.8 Vac. A triac without
potentiometer RP1) and added to the negative setpoint connections and no power applied can be checked for a
voltage from RP2. A sawtooth voltage signal is go-no go condition with an ohmmeter. The gate to MT1
generated by U2 from a constant current source resistance for a power triac (20-40A) should be between
charging capacitor C4. The value of C4 determines the 50 and 100 ohms; there should be infinite resistance
burst period of the triac output (typically 8 seconds). between MT1 and MT2.
The triac gate output pulse current is about 60mA. The
triac is triggered in quadrants II and III. Synchronization 2.4.4 CAPACITOR
is provided by resistor R10. Its value determines the Shorted capacitors have 0V across their terminals.
trigger pulse length. Open capacitors can be located by using a good capaci-
tor connected in parallel with the capacitor under test
and observing the resulting effect.

2–1
 SECTION 2 - TROUBLESHOOTING - A-CONTROL
Leaking capacitors will often have a decreased voltage
across their terminals.

NOTES:

________________________________________________

________________________________________________

________________________________________________

________________________________________________

________________________________________________

2–2
 SECTION 2 - TROUBLESHOOTING - A-CONTROL

2.5 BLOCK DIAGRAM

120/240V
Power Supply 60/50Hz
D1,C1,R11 Line

Cabinet
Return
+6.8V
-8.6V
Set Point Pot

Rate Control Pot Comparator,

Power Supply,
Triac Driver
Amplifier U1 U2

Thermocouple
Power Triac
25A, 400V

Feedback Muffle

2–3
 SECTION 2 - TROUBLESHOOTING - A-CONTROL

2.6 SCHEMATIC

2–4
 SECTION 2 - TROUBLESHOOTING - A-CONTROL

2.7 CONTROL CIRCUIT BOARD

Temperature Meter
Rate Control Connection Triac Gate

Muffle
Connections

Setpoint Thermocouple Proportional Control iC

Potentiometer Amplifier

2–5
 SECTION 2 - TROUBLESHOOTING - A-CONTROL

2.8 WIRING DIAGRAM

230V
LINE CORD

230V
RECEPTACLE
NOTE: A1750 - 250V,20A
LINE CORD
WHT
WHT
120V LINE GRN/YELL
CORD
BLK CABINET
GND
230V
A-1750

230V HOOK UP
HEATING
PLATE
C D DOOR SAFETY
RIAC HEATSINK P1 P6 SWITCH
120V HOOK
TRIAC
UP AND
1750
MUFFLE

BLK WHT CONTROL

WHT DRAWER
GND
RED
TAN GRN/YELL
P1 P5

AC1 ROUTE ALL MUFFLE

THERMOCOUPLE WIRES THRU HERE
MT2 MT1
AC2
WHT/BLK A
ORN TOP
GATE B TERMINALS
BLK
A
B
RED
YELL

POWER SWITCH
A B
SETPOINT ADJUST C D

ANALOG PANEL METER

RELAY FOR A-1750 ONLY

2–6
 SECTION 3 - ADJUSTMENT/CALIBRATION - A-CONTROL

3.1 SCOPE 3.4 CIRCUIT BOARD CALIBRATION

This section gives the procedures to be used for the Calibration of the VULCAN circuit board is performed in
calibration and specification verification of the VULCAN. one single step.
The furnace specifications are given in the Owner &
Operator’s Manual. 3.4.1 REQUIRED TEST EQUIPMENT
- Multimeter
3.2 FACTORY REPAIR - Pot adjustment tool

DENTSPLY Ceramco maintains a factory repair WARNING

With control drawer opened, dangerous voltage points
department for those customers not possessing the
may be exposed. Contact with any of these points could
necessary personnel or test equipment to maintain the cause serious injury.
VULCAN. If a unit is returned to the factory for
calibration or repair, a detailed description of the 3.4.2 TEMPERATURE
specific problem should be included to minimize Disconnect the power cord from the wall outlet and
turnaround time. Call factory for RMA number before open the control drawer. Connect the black lead of the
shipping at 909-.795.2461. ohmmeter to the red thermocouple connection on
temperature meter. Touch the red lead of the ohmmeter
3.3 ADJUSTMENTS to the leg with a circle on R13. Adjust RP1 to read 1060
ohms on the ohmmeter.
3.3.1 DOOR, LIFT DRAG ADJUSTMENT
The lift drag force is controlled by a set of friction On models A-550 rated at 120V the potentiometer RP3
washers on each of the upper pivot arms. If the drag should be adjusted the following way:
becomes too stiff (too hard to open and close furnace)
or too loose an adjustment can be made using the Touch the black lead of the ohmmeter to pin 3 of U3 and
following procedure: the red lead to the leg of R14, see figure 7.2. Adjust RP3
to read between 19 and 20 Kohm on the ohmmeter. This
TOOLS: 5/32" Allen Wrench adjustment limits the amount of current going thru the
muffle by about 15% in order to comply with safety
- Turn the allen head screws on the upper side of the agency rulings. For all other models RP3 should be fully
furnace either clockwise to tighten or counterclockwise clockwise.
to loosen the drag force.
As an alternate circuit board calibration, without the use
of an ohmmeter, bring the furnace temperature to the
NOTE: desired level. At steady state temperature insert a
Equal adjustment should be made on each side. Turn thermocouple, connected to a temperature monitor, into
screws only 1/6 of a revolution at a time when making
the exhaust opening of the furnace and after
adjustment.
stabilization read the muffle temperature. Compare this
reading with the temperature meter reading of the
Connect DMM to PCB as shown in Figure 7-2: furnace. In several steps adjust RP1 to obtain equal
a. For all 120V Units: Adjust RP# to read 19K-20K Ohms readings. Allow ample time between adjustment steps
b. For all 220V-240V Units: Adjust RP3 Fully Clockwise (CW) since only a few watts are added/subtracted which each
adjustment of RP1.

Black Lead to U3 Front of Control Drawer Red Lead to

Pin 3 Here R14 Here
Figure 7-2
3–1
 SECTION 4 - CIRCUIT DESCRIPTION - 3-STAGE

4.1 INTRODUCTION 4.2.4 POWER SUPPLY

One DC power supply voltage is generated on the
The purpose of this section is to familiarize the user or control circuit board +5V.
service personnel with the circuit level operation of the
VULCAN. This knowledge is necessary to aid in trou- 4.2.4.1 +12V SUPPLY
bleshooting of a unit's failure and may also allow the The +12 VDC is generated from 15 watt switching power
user to gain greater insight into the VULCAN’s versatility supply mounted onto the main control PC board.
for particular applications. A detailed description is
4.2.4.2 +5V SUPPLY
given for the following circuit functions:
Refer to schematic, page 5-9. DC voltage from the output
* Display Readout
of the switching power supply is used by the +5V linear
* Front Panel Control
regulator U3 to generate the +5V. The capacitor C21
* Muffle Control
provides additional filtering. The 1.23V reference diode
* Power Supply
D1 generate their outputs from this supply.
* Motor Drive Control (option for 3-Stage)
*Temperature Measurement
4.2.5 MOTOR DRIVE CONTROL (3-550 PD)
The +12VDC motor which moves the door vertically is
The muffle temperature is derived from a Thermocouple controlled by a 16 pin motor controller/driver I.C. This
(type "K") which generates an output voltage of up to I.C. provides all necessary functions for a complete
50mV. This feedback signal is then manipulated by the closed loop system. A two wire cable connects the
electronics to control the muffle temperature. motor to the 1 Amp H-bridge switch on the I.C. The
microprocessor (U9) activates the H-switch through two
4.2 CIRCUIT DESCRIPTION 3-STAGE input pins. If both are low the motor will turn in one
direction, if both are high the motor turns in the
4.2.1 LCD DISPLAY READOUT opposite direction. A third pin sends a signal from the
The display board converts serial data from the motor controller/driver I.C. to the microprocessor when
microprocessor to 8-bit parallel data. Each byte the motor has stalled (up or down position).
transferred is either a command or a data byte
depending on the state of the two control bits RS and E 4.2.6 FAN DRIVE CONTROL 3-550A/1750A
(DIS ENA). The 16 character LCD module is controlled by The air exchange fan is controlled by means of the front
the microprocessor via its Serial Peripheral Interface panel membrane switch. Speed selections are from
(SPI) port. The display is updated every 0.5 sec or when 0 - 9 (0 is off and 9 is highest speed). Speed 1 selection
a corresponding front panel key has been activated. changes the air in the muffle twice a minute.

4.2.2 FRONT PANEL CONTROL NOTES:

The power on/off switch switches the AC line voltage.
The membrane switches are arranged in a 8x4 matrix. ________________________________________________
The microprocessor scans the entire matrix every 50
msec by setting one column at a time to a logic 0 and ________________________________________________
then reading the rows. Once a contact closure has been
detected this value is stored. ________________________________________________

4.2.3 MUFFLE CONTROL ________________________________________________

The microprocessor (U9) sends a serial digital signal to an
octal peripheral driver (U6) which in turn converts and
latches it to parallel data. This data is then used to drive
several peripheral devices. U9 is connected to an opto
isolator (U7). The isolator's output is connected to the
gate of the muffle triac. The muffle triac may be activated
anytime during an AC cycle, but once activated it can only
be opened when the AC sine wave passes through 0
volts. U9 accesses U7 0.5 msec before zero crossing to
turn the triac off. At this time a value calculated by the
control routine determines how much time should elapse
before the triac is turned on again.

4–1
 SECTION 5 - TROUBLESHOOTING - 3-STAGE

5.1 FACTORY REPAIR 5.3 TROUBLESHOOTING GUIDES

DENTSPLY Ceramco maintains a factory repair 5.3.1 POWER SUPPLY
department for those customers not possessing the To determine a faulty power supply use the table on
necessary personnel or test equipment to maintain the page 5-3. To troubleshoot a faulty power supply use the
VULCAN. If a unit is returned to the factory for procedures listed on page 5-4. If the desired results are
calibration or repair, a detailed description of the obtained in each of the steps in the tables, replace D43,
specific problem should be attached to minimize U9 or U7 as appropriate.
turnaround time. Call factory for PR number before
shipping at 1-800-835-6639. 5.3.2 MICROPROCESSOR
Generally, when the furnace is totally nonfunctional,
i.e., display is unintelligible, no display, random relay
5.2 BEFORE YOU START
clicking, no key response, or the front panel LED’s stay
Since no troubleshooting guide can possibly cover all on at power up, the problem is in the microprocessor
the potential problems, the aim of this guide is to give a section. However, before troubleshooting this section,
methodology which, if applied consistently, will lead to check the appropriate dedicated circuits for correct
the problem area. Therefore , it is necessary to operation. Detailed reading of the circuit description is
familiarize yourself with the VULCAN by reviewing the also very important. See page 5-5 to troubleshoot the
functional description and the detailed circuit microprocessor.
description (Section 4) in conjunction with the
5.3.3 PERIPHERAL DRIVE
schematics (Section 5). Successful troubleshooting
The peripheral driver U6 is accessed at every line
depends upon understanding the circuit operation
voltage zero crossing by the microprocessor. The logic
within each functional block as well as the block
state of the eight output drivers, Y0 -Y7, is latched into
relationships.
the shift register at time t0 on the high to low transition
of SIOE. Input data present at the SI input is clocked
WARNING
With covers removed, dangerous voltage points may be into the shift register on the high to low transition of
exposed. Contact with any of these points could cause SCLK. See page 5-6 to troubleshoot the peripheral
serious injury. driver.

The intent of this section is to provide the information to 5.3.4 MOTOR DRIVE (OPTIONAL ACCESSORY)
return the VULCAN to proper operation. Information is The motor driver U8 is accessed by the microprocessor
divided into two parts. Part one contains the overall to lift or lower the door. U8 provides a feedback to the
furnace troubleshooting block diagram which is useful microprocessor to indicate an overcurrent condition
in isolating defective blocks within the furnace. Part two which is set at approximately 1.00Amp by resistor R3.
consists of a series of circuit guides , one for each block See page 5-6 to troubleshoot the motor driver.
shown in the block diagram, that provides settings and
measurements for troubleshooting an individual block. 5.3.5 ANALOG CIRCUITRY
Also, each circuit guide references related schematics The reference voltages used to control temperature and
and circuit descriptions. Inspect the components, compare voltage signals are derived from the output of
wiring and circuit boards of the VULCAN for damage. U1-7 (+5V) and D1. See schematics for troubleshooting
Finally, ensure that the fuses are intact and the internal individual components. See page 5-6 to troubleshoot
power supplies are good. the analog circuitry.

5.2.1 ISOLATING A PROBLEM 5.3.6 DISPLAY BOARD

To successfully troubleshoot this furnace, the symptoms Serial data present on the input of U1-14 and U2-2 is
must first be identified, the faulty block isolated, then transfered to the shift register on the logic “0” to logic
analyzed, and finally the defective component located “1” transition of the Clock input pulse. Information
and replaced. present at any register of U1 is transferred to its
respective latch when the Strobe is high (U1-7). A serial
After the block is isolated, refer to the appropriate to parallel conversion takes place. As long as the Strobe
functional circuit guide. is held high (“1”) the latches will accept new data. The
LCD display module will accept valid data on D0 - D7
The circuit guide provides some but not necessarily all when the Enable (J1-6) goes from a high to low
of the possible failure modes for a particular circuit. transition. See page 5-7 to troubleshoot the display
Where applicable, a furnace setup procedure is given to circuit board.
help isolate the problem for a particular failure mode.
5–1
 SECTION 5 - TROUBLESHOOTING - 3-STAGE
5.3.7 FAN DRIVE (OPTIONAL ACCESSORY) 5.4.3 TRIAC
The 12V DC fan is controlled by a FET device which is The gate to power line return voltage (K1) under load
activated by the microprcessor. At its highest setting measures typically 1-2 Vac, while the MT2 to return
(9), the fan receives the full 12V DC. At lower settings voltage measures between 1.3-1.8 Vac.
the fan receives +12V pulses, to reduce the rpm's.
A triac without connections can be checked for a go-no
5.4 TROUBLESHOOTING COMPONENTS go condition with an ohmmeter. The gate to MT1
resistance for a power triac (20-40A) should be between
5.4.1 DIODE 50 and 100 ohms; there should be infinite resistance
A diode (except a zener) is defective if there is greater between MT1 and MT2.
than 1 Vdc (typically 0.7 Vdc) forward voltage across it.
5.4.4 CAPACITOR
5.4.2 OPERATIONAL AMPLIFIER Shorted capacitors have 0V across their terminals.
Generally the “+” and “-” inputs of an operational Open capacitors can be located by using a good
amplifier will have less than 15 mV voltage difference capacitor connected in parallel with the capacitor under
when operating under normal conditions. (U1). When test and observing the resulting effect. Leaking
the output of the amplifier is connected to the “-” input capacitors will often have a decreased voltage across
(voltage follower connection), the output should be the their terminals.
same voltage as the “+” input voltage; otherwise, the
amplifier is defective. 5.4.5 LOGIC LEVELS
Microprocessor: High +3.5 - +5.0V
If the output voltage stays at maximum positive Low 0.0 - +1.0V
(typically 1/3 of the supply voltage), the “+” input
voltage should be more postitive than the “-” input 74LSXXX: High +2.0 - +5.0V
voltage. Low 0.0 - +0.5V

4XXX (CMOS): High +3.5 - +5.0V

Low 0.0 - +1.5V

5–2
 SECTION 5 - TROUBLESHOOTING - 3-STAGE

5.5 ERROR CODES

ERR 1 MUFFLE OVER TEMPERATURE

The controller monitored a temperature above
°C. This could mean a faulty thermocouple (mV
reading too high) or an erratic thermocouple
performance (the temperature readout is not
stable at elevated temperatures).

ERR 2 OPEN TC DETECTED

To check for open TC, turn power to furnace off
and short TC input terminals. Turn power back
on. If ERR 2 disappears, then replace TC.
Possible solutions:
Change PCB if problem persists.

ERR 3 TMAX OVER TEMP

The controller monitored a temperature above
Tmax + 20°C. This could mean:
* The Tmax was set up too low for this program
* The destination temperature is relatively low
compared to the programmed heat rate, eg.
too much temperature overshoot.

ERR 8 EEPROM READ/WRITE ERROR

(APPLIES TO 9493980 ONLY)
Program parameters entered during the idle
mode are transferred and stored in a 16K-bit
Electrically Erasable Programmable Read Only
Memory (EEPROM) device. The serial data on
U10 is monitored and any abnormal behavior
from the devices’ specs is answered with an
error code. Press ENTER and check:
* Data, Clock train on U10-5,6
* Replace device

ERR 19 NO LINE FREQUENCY DETECTED

(APPLIES TO 9493980 ONLY)
* Check U1 A-1, 100 or 120 Hz pulse train
* Remove Power

5–3
 SECTION 5 - TROUBLESHOOTING - 3-STAGE

5.6 DIAGNOSTIC TABLES

FURNACE SETUP COMMON ERRORS

Symptom Possible Setup Error

Display blank No line voltage

Power switch failure
J8 disconnected

No Setup functions after ENTER Furnace was in start cycle at power down

Muffle does not heat after power up Not in start cycle

Door switch not closed

No door movement after switch is pressed Furnace is in TEST mode

Motor connector J5 loose

POWER SUPPLY VOLTAGES

Output Voltage Output Test Input Test

Voltage Tolerance Ripple At Ripple At

+12V +/-350mV 0.02Vac PT1 & PT4 3Vac PT1 & PT4

+ 5V* +/-250mV 0.02Vac U3-3 3Vac U3-1

* Note: +5VDC is dependent on the presents of the 12VDC, U3 on the main PC Board regulates the +5VDC.

5–4
 SECTION 5 - TROUBLESHOOTING - 3-STAGE

5.6 DIAGNOSTIC TABLES

POWER SUPPLY

Fault Setup Check Results desired

No DC output and no Power off Fuse < 1 ohm

DC to U11-2 (15-30V) Not shorted or open
PT1 to PT4 Not shorted or open

MICROPROCESSOR

Fault Setup Check Results desired

Nonfunctional N/A U9-3, 2 4.9MHz, sinusoid

operation X1 approximately 0-4V
U9-26 >4.5V
U9-9 waveform
U9-10 +5VDC

Power Off/On Listen Relay clicks,Sonar

5–5
 SECTION 5 - TROUBLESHOOTING - 3-STAGE

5.6 DIAGNOSTIC TABLES

PERIPHERAL DRIVE CIRCUIT

Fault Setup Check Results desired

All Y outputs N/A U6-1, 2, 6

high No stuck bits

Turn furnace Display/ No Error codes

Off then On LED's Display OK

Turn furnace D2, D3, D4, D6 Not shorted or open

Off

MOTOR DRIVE CIRCUIT

Fault Setup Check Results desired

No door up or down Furnace in idle U8-16 +12 VDC

when switch is activated Disconnect J5 U8-10-15
Turn furnace on
Activate switch
Activate switch
Turn furnace off
Turn furnace on U13-15 digital high

Motor switch Other keys respond

At up or down Add mA meter in Stall > 550 mA at up

position series at J5 current or down

5–6
 SECTION 5 - TROUBLESHOOTING - 3-STAGE

5.6 DIAGNOSTIC TABLES

ANALOG CIRCUITRY

Fault Setup Check Results desired

Muffle heats but N/A YELL2 TC yellow connected

display shows U4 Gain approx. 20
same temperature D1 1.23V

Erratic temperature D1 1.23V stable

display N/A U4-11 & 12 DC stable

Temperature drift Hi T = 960°C RED 39-40mV stable

U4-13 mV stable
(.2mV/°C ambient
increase typical)

Turn furnace off Reconnect No Err2 at elevated

TC wires temperatures

DISPLAY BOARD

Fault Setup Check Results desired

LCD dots are all Furnace in idle J8-1 +5V

on or off at power up
J4-8 Tight fit

No LED's light up Perform power up Front Panel LED's turn off one
by one
N/A J8-4 +12V

One LED does not come on Turn furnace off LED Not open or
shorted

LCD display is darker Turn furnace off Temperature on Less than 40°C
panel

Turn furnace on Temperature on LCD lighter shade

panel

5–7
 SECTION 5 - TROUBLESHOOTING - 3-STAGE

5.7 BLOCK DIAGRAM

Switching 90-264V
Power Supply 60/50Hz
+12V
Pg 5-9

U1, U2
Thermocouple
Zero Crossing
AMP U1 U9
U4 U8
Multiplexed A/D Microprocessor Motor Drive M

Pg 5-11
D1 + RT1
Pg 5-11
Cold Jct. Ref Temp U6
Membrane Switches Peripheral
Pg 5-10 Pg 5-9
Drive

K1, K2
Display Board
Muffle Relays

16 Character LCD Pg 5-9

Triac driver
U2 U1 Pg 5-9
Serial to LED Driver
Parallel (10)
Sonar

5–8
 SECTION 5 - TROUBLESHOOTING - 3-STAGE

5.8 SCHEMATICS

POWER SUPPLY

5– 9
 SECTION 5 - TROUBLESHOOTING - 3-STAGE

5.8 SCHEMATICS

TEMPERATURE CIRCUIT

LCD DISPLAY CIRCUIT

5 – 10
 SECTION 5 - TROUBLESHOOTING - 3-STAGE

5.8 SCHEMATICS

MICROPROCESSOR CIRCUIT

5 – 11A
 SECTION 5 - TROUBLESHOOTING - 3-STAGE

5.8 SCHEMATICS

5 – 11B
 SECTION 5 - TROUBLESHOOTING - 3-STAGE, PD, A

5.9 WIRING DIAGRAM

5 – 12
 SECTION 6 - ADJUSTMENT/CALIBRATION - 3-STAGE

6.1 SCOPE 6.3.2 DOOR, LIFT DRAG ADJUSTMENT

The lift drag force is controlled by a set of friction
This section gives the procedures to be used for the washers on each of the upper pivot arms A wave spring
calibration and specification verification of the VULCAN. should maintain a relatively constant force even after
The furnace specifications are given in the Owner & several thousand cycles. If the drag becomes too stiff
Operator’s Manual. (too hard to open and close furnace) or too loose an
adjustment can be made using the following procedure:
TOOLS REQUIRED: 5/32" Allen Wrench
6.2 FACTORY REPAIR
- Turn the allen head screws on the upper side of the
DENTSPLY Ceramco maintains a factory repair furnace either clockwise to tighten or counterclockwise
department for those customers not possessing the to loosen the drag force.
necessary personnel or test equipment to maintain the
VULCAN. If a unit is returned to the factory for Note: Equal adjustment should be made on each side.
calibration or repair, a detailed description of the Turn screws only 1/6 of a revolution at a time when
specific problem should be included to minimize making adjustment.
turnaround time. Call factory for PR number before
shipping at 1-800-835-6639.
6.4 CIRCUIT BOARD CALIBRATION
6.3 ADJUSTMENT/CALIBRATION Calibration of the VULCAN circuit board is performed in
two steps: Software and hardware.
6.3.1 TEMPERATURE
To verify the muffle temperature at a given setpoint
WARNING
insert the tip of a temperature probe into the exhaust With control drawer opened, dangerous voltage points
opening far enough to reach the center of the muffle. may be exposed. Contact with any of these points could
Connect the other end of the probe to a temperature cause serious injury.
meter and let the meter reading stabilize. Once a steady
reading is obtained on the temperature meter divide the WARNING
setpoint (display) temperature by the meter Observe antistatic procedures when touching
temperature and multiply the result by the current Tcal circuit board components which can be damaged by
value. The result will be the new Tcal temperature. static electricity.

Example:
The temperature meter shows a reading of 520°C at a
setpoint of 500°C. The Tcal temperature in the setup
mode shows 1000°C.

The new setup temperature Tcal is now found by the

following calculation:

500°C
520°C
Tcal = .961 x1000 = 961°C

Note: Abort the cycle before turning off the furnace.

This is the new Tcal temperature. Turn the furnace off
and then on again, wait for Setup? on the display and
press ENTER until Tcal = 1000°C appears. Key in 961 and
press ENTER.

6–1
 SECTION 7 - SERVICE PARTS - A-CONTROL & 3-STAGE

7.1 ORDERING INSTRUCTIONS

To order parts, select the part number required from the
exploded view drawings on page 7.1. through page 7.6.
The 130, 550, 1750 numbers refer to the particular size of
furnace where the part number is different depending
on the size.

When ordering parts please have the following

information available:

1. Serial number of furnace. Hardware Kit: 9493454

2. Date purchased. (Contains a selection of the fasteners used in the
3. Purchased where. furnaces.)
4. Symptom of failure.
5. Part number of replacement part.
6. Preferred method of shipment.

7.2 MUFFLE AND THERMOCOUPLE

HEATING PLATE ASSY
New 9493426*, 130 MUFFLE INSULATION
230V (9493364), 550 (9493341), 130
100, 120V (9493470), 550 (9493361), 550
(9493392), 1750 (Factory Repair), 1750

THERMOCOUPLE
(9493342) 130, 550
(9491747) 1750

MUFFLE SPRINGS
(9390705)

FLOOR TRAY
(9353053), 130
(9353057), 550
(9353060, 1750

MUFFLE ASSY COMPLETE:(Includes muffle

insulation, and 2 heating plates)
(9493422), 130
230V (9493423), 550
FRONT PANEL 100, 120V (9493471), 550
(9493315), 130 (Factory Repair), 1750
(9493355), 550
(9493385), 1750

NOTE: Part shape and assembly will vary between the three * Note: 9493340 was replace with 9493426. IF your model -130
furnace sizes. was built before August 2011 you need to replace both muffle
plates. Also order replacement fuse part no. 9320137.

7–1
 SECTION 7 - SERVICE PARTS - 3-550A & 3-550PD

7.3 MUFFLE (3-550 PD & AIR EXCH)

MUFFLE INSULATION
HEATING PLATE ASSY (9493780), 550 PD
230V (9493364), 550 PD
100, 120V (9493470), 550PD

THERMOCOUPLE
(9493342) 550 PD

FLOOR TRAY
(9353057), 550

MUFFLE ASSY COMPLETE:(Includes muffle

insulation, and 2 heating plates)

230V (9493778), 550 PD

FRONT PANEL 100, 120V (9493779), 550 PD
(9493808), 550 PD (9493996), 550A
(Factory Repair), 1750A

7–2
 SECTION 7 - SERVICE PARTS - A-CONTROL, 3-STAGE, 3-550PD

7.4 CABINET PARTS

NOTE: To convert to configurations shown, 9495115 - Retrofit Kit, is

available for furnaces built prior to S/N 0626xxx.
(9493534) REAR PANEL
3-550PD FURNACE
CABINET ASSY
(9493320) 130 FURNACES
(9493354) 550 FURNACES
POWER CORD (120 & 230V) (9493384) 1750 FURNACES
(9390115) 130, 120V (9493807) 3-550 PD FURNACE
(9309118) 230V US
(9309117) 230V EURO
(9493653) 1750 EURO
(9409131) 1750 US
(9390118) 550, 120V

120V SOCKET ASSY

(9302072) FUSE, 20 Amp
(9320136) FUSE, 16 Amp, 120V
(9320137) FUSE, 12 Amp, 120V

(9494462)
ADAPTER PLATE, 120V

SOCKET ASSY.
LOCATION
(9493338) DOOR SWITCH

For - 130 Models (9494462) ADAPTER PLATE, 120V

For - 550 Models (9493822) ADAPTER PLATE, 120V

130, 230V SOCKET ASSY 550, 230V SOCKET ASSY

(9320197) FUSE, 10 amp

(9492995) SOCKET ASSY., 200/240V (9495104) SOCKET ASSY., 200/240V

(9495099)
ADAPTER PLATE, 200/240V

(9320069) FUSE, 10 amp

(9492996) ADAPTER PLATE,

200/240V (9311017A) FUSE HOLDER

7– 3
 SECTION 7 - SERVICE PARTS - A-CONTROL, 3-STAGE

7.4 CABINET PARTS

FAN ASSY
(9493986) 3-550A, 3-1750A FAN DUCT ASSY
(9493970) 3-550A, 3-1750A

7.5 DOOR PARTS

DOOR SPRING
(9493368), 130
(9493908), 550
(9492754), 1750 (2 PL)
SCREW 10-32 x .50 KEP
(4 PL)

DOOR BOTTOM
(9493313), 130
(9493351), 550
(9493381), 1750

DOOR INSULATION
(9493325), 130
(9493365), 550
DOOR
(9493393), 1750
(9493321) , 130
(9493350), 550
(9493380), 1750
HANDLE
(9390246)

7– 4
SECTION 7 - SERVICE PARTS - A-CONTROL

7.6 A- CONTROLLER PARTS

FUSE (20A) - S/N 9525 and SCREW, 6-32 x .375

CONTROL PCB 9320072 earlier
(R9493348) 100-120V A-130
(R9493449) 200-240V A-130 RELAY, (1750 ONLY)
(R9493349) 100-120V A-550 (9320075)
(R9493450) 200-240V A-550
(R9493451) 200-240V A-1750

TRIAC
(9303015)

HEATSINK

PYROMETER
(9390451)

CONTROL DRAWER
KNOB, SET POINT (9493316) A-130
(9355026) (9493356) A-550
(9493386) A-1750
POWER SWITCH
(9306038)
OVERLAY
(9354229) A-130
(9354230) A-550
(9354231) A-1750

7– 5
 SECTION 7 - SERVICE PARTS - 3-STAGE, 3-550PD

7.7 3-STAGE CONTROLLER PARTS

CONTROL PCB, 3-550 PD,A

(R9493446) 100-125V SCREW, 6-32 x .375

s
Replaced by R9495232 (Not Shown)
(R9493447) 200-240V
SCREW, 6-32 x 1.75
TERMINAL BLOCK
(9390487)

TC WIRES

DISPLAY PCB
(R9493347)

FUSE (1A)
TRIAC
9320071
(9303015)

HEATSINK

CONTROL DRAWER
MEMBRANE SWITCH (9493376, 3-130)
(9494063, 3-550A, POWER SWITCH
(9493379, 3-550)
3-1750A) (9306038)
(9493387, 3-1750)

7– 6
 SECTION 7 - SERVICE PARTS - 3-550PD

7.8 LIFT MECHANISM PARTS

NUT, 1/4-20 HEX

SCREW, 10-32 SEM

BRACE
PIVOT ARM (9493363)

BRACKET, MOTOR LINKAGE

(9493532)

BOLT, SHOULDER .375

SCREW, #8-32 SEM

BRACKET, MOTOR
(9493362)

SCREW #8 X.375

SCREW, #8 X .50

BRACKET, SPRING

MOTOR POWER DOOR

(9493777)

SCREW, 1/4-20
SPRING
(9356016)

LNUT 1/4-20 HEX NYLOK

7–7
 SECTION 8 - DISASSEMBLY/REASSEMBLY - 3-STAGE

8.1 CONTROL DRAWER REMOVAL 8.2 TRIAC

TOOLS: TOOLS:
Phillips #2 screwdriver Phillips #2 screwdriver, 1/4" nut driver, needle nose pliers

- To gain access to the electrical components and most 8.2.1:

other service jobs, removal of the control drawer is Follow steps 8.1.1 through 8.1.2 of CONTROL DRAWER
required. REMOVAL

WARNING:
Disconnect power cord from wall outlet
before attempting to service the furnace.

8.2.2:
Disconnect wires from triac located at the rear center
of the control drawer.(use pliers to assist)

8.2.3:
Remove 2 nuts and lift triac off heatsink.

8.1.1:
Remove 2 screws from bottom front of the furnace Use Heatsink (white)
compound from old triac.
8.2.4:
Replace with new triac and note orientation.

Insert screwdriver
if needed

8.1.2: 8.2.5:
Slide control drawer towards you. Connect wires to triac according to Wiring Diagram 2.9
Note: A bladed screwdriver may be needed (A Control) or 5.9 (3 Stage) Make sure connections are tight

8–1
 SECTION 8 - DISASSEMBLY/REASSEMBLY - 3-STAGE

8.3 MEMBRANE SWITCH

TOOLS:
Phillips screwdriver
Knife of other sharp edged device

8.3.1:
Follow steps 8.1.1 through 8.1.2 of CONTROL DRAWER
REMOVAL

Control PCB
Membrane Switch Control Drawer
8.3.5:
Place the new membrane switch by locating the
bottom edge against the bottom of the recess.

Membrane Switch

8.3.2: Control PCB

Disconnect ribbon cable at control PCB DOT

Membrane Switch

8.3.6:
Connect ribbon connector

8.3.3:
Peel off membrane switch (Use knife if needed).

Membrane Switch Control Drawer

8.3.4:
Clean front panel surface with isopropyl alcohol.
Allow to dry thoroughly.

8– 2
 SECTION 8 - DISASSEMBLY/REASSEMBLY - 3-STAGE

8.4 DISPLAY PCB

TOOLS: Phillips screwdriver

CAUTION!
Use proper ESD grounding techniques when handling
electronic components

8.4.1:
Follow steps 8.1.1 through 8.1.2 of CONTROL DRAWER
REMOVAL

8.4.5:
Connect grey ribbon connector. Bend away from
Display PCB so it won't cut into ribbon.

8.4.2:
Disconnect grey ribbon connector.

8.4.3:
Remove from snap-on standoffs.

8.4.4:
Replace with new Display PCB.
8– 3
 SECTION 8 - DISASSEMBLY/REASSEMBLY - A-CONTROL

8.5 A-CONTROL PCB

TOOLS:
Phillips screwdriver
Needle nose pliers
3/8" nut driver or wrench
1/4" nut driver
13 mm nut driver or pliers

CAUTION!
Use proper ESD grounding techniques when handling
electronic component 8.5.5:
Remove knob by pulling out and nut (13mm nut driver or
pliers).
8.5.1:
Follow steps 8.1.1 through 8.1.2 of CONTROL DRAWER
REMOVAL.
Remove

muffle
wires

AC1 MT2
AC2
MT1

8.5.2:
Disconnect wires AC1, AC2, MT1, MT2 and 4 muffle wires
from power board.

8.5.3: Orange
Disconnect orange wire from triac. 8.5.6:
Remove 2 screws.

Pyrometer
Red from PCB Reverse steps for reassembly.
Red from Muffle

Top CAUTION! Do not overtighten nut

7.8 Fig. G View

Yellow from PCB

Yellow from Muffle

8.5.4:
Disconnect wires from pyrometer.

8– 4
 SECTION 8 - DISASSEMBLY/REASSEMBLY - 3-STAGE

8.6A 3 STAGE CONTROL PCB - 9493980

TOOLS:
Phillips screwdriver, Slotted screwdriver, Needle nose pliers

CAUTION!
Use proper ESD grounding techniques when handling
electronic components
8.6.6: Remove thermocouple wires

8.6.1: Follow steps 8.1.1 through 8.1.2 of CONTROL DRAWER

REMOVAL.

DOT

8.6.2: Disconnect wires from power switch.

8.6.7: Remove 5 screws.

8.6.3: Disconnect ribbon connectors.

8.6.8: Squeeze plastic standoff and lift circuit board.

8.6.4: Remove relay and door switch wires.

8.6.9: Replace with new circuit board. Tighten

5 screws. Follow wiring diagram 5.9 on page 5-12.
8.6.5: Disconnect wires from triac.

8– 5
 SECTION 8 - DISASSEMBLY/REASSEMBLY

8.6B 3 STAGE CONTROL PCB – 9495232

CAUTION!
TOOLS: Use proper ESD grounding techniques when handling
Phillips & Slotted Screwdrivers, Needle Nose Pliers components

Follow steps 8.1.1 through 8.1.2 of Control Drawer

REMOVAL

Figure 1 - Disconnect wires from Figure 2 - Disconnect Ribbon Cables Figure 3 - Remove Relay Wires
Power Switch

Figure 4 -Remove Door Switch Wires Figure 5 - Remove Wire From Triac Figure 6 - Remove Thermocouple
Wires

Figure 7 - Remove 4 Screws from PCB Figure 8 - Squeeze standoff with Figure 9 - New PCB Replacement
needle nose pliers & remove PCB

Figure 10 - Insert PCB in standoff, Figure 11 - Follow Steps #1 thru

tighten 4 Screws #6 for PCB Connections

8 – 5A
 SECTION 8 - DISASSEMBLY/REASSEMBLY

8.7 DOOR ASSEMBLY/ ADJUSTMENT

TOOLS:
5/32 Allen wrench
Phillips head screwdriver

If the door feels too stiff or too loose when lifting up and
down, a tension adjustment can be made from the outside.

8.7.4: If door or door insulation needs replacement,

remove the 4 screws on bottom of door (step 5.7.2) and slide
from slide out assy.

8.7.1: If door tension is too loose tighten the screw on each

side until the desired tension is reached. If too tight, loosen
screw.

8.7.5: Remove 2 screws and slide out door insulation

and spring. If door is to be replaced, remove 2 screws
holding handle.

8.7.2: If door insulation is rubbing against cabinet, loosen 8.7.6: Replace with new insulation or door by reversing steps
the 2 screws on each side of door. 8.7.4 - 8.7.5.

8.7.7: Set spacing as described in section 8.7.3. Important!

Screws must be torqued to 25-30 in-lbs.

8.7.3: Rotate door out from cabinet and tighten 4 screws.

Check to make sure that rope contacts muffle lip when
closed and insulation clears cabinet when lifted.

8– 6
 SECTION 8 - DISASSEMBLY/REASSEMBLY

8.8 HEATING PLATES

TOOLS: Phillips head screwdriver
Small putty knife

Note: Like the headlights on a car, if one heating

plate burns out, the other will likely burn out soon.
Brake bond with
Therefore, it would be advisable to replace both
putty knife
plates at once.

WARNING: rotate in
Disconnect power from the wall outlet before
attempting to service the furnace! 8.8.3: Pull out bad plate(s) (Rotate bottom of plate
toward center of muffle). Be careful when pulling leads
thru holes in muffle.
8.8.1 Follow steps 8.1.1 - 8.1.2 of CONTROL DRAWER
REMOVAL.
A-CONTROL
(130, 550) 100, 120V HOOK UP (130, 550)
(1750) 230V 230V HOOK UP

feed wires thru

Black marked
P1 P6 bushings (one wire
lead
per bushing)
TAN Black marked
lead
P1 P6

3-STAGE
(130, 550) 100, 120V MUFFLE (130, 550) 230V
MUFFLE WIRING
8.8.4: Replace with new plate(s). There are brass
WIRING (1750), 230V bushings located in the heatshield below the muffle
holes. Cut tie wraps located on terminals' insulation.
Slide the piece of insulating sleeve (provided) over the
existing ones and tie wrap at 1" below the heat shield. It
may take a few attempts to locate this hole with the
muffle terminal

TAN W/BLK MARK

8.8.1: Disconnect muffle wires from plate(s) to be

replaced. (refer to wiring diagram 2.9 for A-Control and
Apply white adhesive
5.9 for 3-stage control.) (optional)

8.8.5: Optional: a syringe of ceramic adhesive is

provided to hold plates secure to sides. Stuff newspaper
in muffle until adhesive sets (1 hr). There will be some
movement of the plates without the adhesive.

8.8.6: Connect muffle wires from plate(s) to control PCB.

Refer to wiring diagram 2.8 for A-Control or 5.9 for 3 stage
control. (See step 8.8.1)

8.8.7: Install floor tray

8.8.2: Remove floor tray 8.8.8: Install control drawer by reversing steps 8.1.1 -
8.8.5

8– 7
 SECTION 8 - DISASSEMBLY/REASSEMBLY

8.9 COMPLETE MUFFLE REPLACEMENT

TOOLS: Phillips head screwdriver; small flat head
screwdriver; needle nose pliers

WARNING:
Disconnect power from the wall outlet before
attempting to service the furnace!

8.9.1: Follow steps 8.1.1 - 8.1.2 of CONTROL DRAWER

REMOVAL.
A-CONTROL
8.9.6: Pull/pry out muffle assy (with attached front
100, 120V HOOK UP 230V HOOK UP panel) from wraparound

P1 P6

TAN

P1 REMOVE SCREW

3 - Stage
230V MUFFLE
100, 120V WIRING
MUFFLE
WIRING 8.9.7: Remove screw used to secure thermocouple
and pull thermocouple from muffle

TAN W/BLK TAN

MARK

TAN W/BLK MARK

REMOVE SPRINGS
8.9.2: Disconnect muffle wires. (Refer to wiring diagram 2.8
for A-Control and 5.9 for 3 stage control.)

8.9.8: Remove muffle retaining springs with needle

REMOVE SCREWS nose pliers. CAUTION: WEAR GLOVES AND EYE
PROTECTION!

8.9.9: Remove muffle assy

8.9.3: Remove 5 or 6 screws on the front top of the

furnace. Remove exhaust port

8.9.4: Open door

muffle wires must pass thru

REMOVE SCREWS brass bushings (4 pl)

8.9.10: Replace with new muffle assy by reversing

steps 8.9.1 - 8.9.9. Make sure that muffle wires pass
8.9.5: Remove two screws (one each side) thru brass bushings in heatshield

8– 8
 SECTION 8 - DISASSEMBLY/REASSEMBLY

8.11 THERMOCOUPLE (3 STAGE CONTROL)

TOOLS: bladed screwdriver
bracket phillips head screwdriver
1/4" nutdriver

Wraparound WARNING:
Disconnect power from the wall outlet
Front Panel
8.9.11: Front panel must insert into offset bracket in before attempting to service the furnace!
wraparound
8.11.1: Follow steps 8.1.1 - 8.1.2 of control drawer removal
8.9.12: Check muffle resistance to verify wiring is
correct before securing control drawer: 8.11.2: Follow steps 8.9.3 - 8.9.7 from previous page for
100V 120V 200-240V muffle replacement for furnaces without a rear access panel.
Note: All 1750 furnaces and all furnaces with S/N date codes
A-130, 3-130 11.5 ohms 11.5 ohms 32 ohms
after 9701 will have rear access panel so that muffle will not
A-550, 3-550 8 ohms 8 ohms 24 ohms need to be removed to service thermocouple (see step
A-1750, 3-1750 12 ohms 8.11.6 for details).

8.10 THERMOCOUPLE (A-CONTROL)

remove nut
TOOLS: bladed screwdriver phillips head screwdriver, 3/8"
nutdriver, wrench, 1/4" nutdriver

WARNING:
Disconnect power from the wall outlet
before attempting to service the furnace!

8.10.1: Follow steps 8.1.1 - 8.1.2 of control drawer removal

8.10.2: Follow steps 8.9.3 - 8.9.7 from previous page for

muffle replacement for furnaces without a rear access panel. 8.11.3: Remove nut which holds thermocouple to
Note: All 1750 furnaces and all furnaces with S/N date codes control drawer.
after 9701 will have rear access panel so that muffle will not
need to be removed to service thermocouple (see step
8.11.6 for details).

Pyrometer
Red from PCB
Red from Muffle

Top
7.8 Fig. G
View

Yellow from PCB

Yellow from Muffle
8.10.3: Disconnect thermocouple from pyrometer

remove and replace nut

8.11.4: Disconnect thermocouple from circuit board
red
yel 8.11.5: Replace with new thermocouple by reversing previous
red steps 8.11.1 thru 8.11.4
yel

meter
8.10.4: Remove nut. Replace thermocouple by reversing
previous steps and replace nut.

8– 9
 SECTION 8 - DISASSEMBLY/REASSEMBLY

8.12 COMPLETE MUFFLE REPLACEMENT

TOOLS: Phillips head screwdriver; bladed screw
driver; needle nose pliers

8.12.1: Follow steps 8.1.1 - 8.1.2 of CONTROL DRAWER

REMOVAL.

REMOVE SCREWS

8.12.2: Close door and remove 6 screws on the front

top of the furnace. Remove exhaust port
8.12.6: Pull/pry out muffle assy (with attached front
panel) from wraparound

REMOVE SCREWS

REMOVE SCREWS
8.12.3: Close door and remove six screws
(three each side)

WARNING:
Disconnect power from the wall outlet before
attempting to service the furnace! 8.12.7: Remove screw used to secure thermocouple
and pull thermocouple from muffle
230V MUFFLE
WIRING
100, 120V
MUFFLE
WIRING

TAN W/BLK
TAN
MARK

TAN W/BLK MARK

8.12.4: Disconnect muffle wires. (Refer to wiring 8.12.8: Remove muffle assy by removing 10 screw.
diagram 5.9).

muffle wires must pass thru

brass bushings (4 pl)

8.12.9: Replace with new muffle assy by reversing steps

8.12.1 - 8.12.8. Make sure that muffle wires pass thru
8.12.5: Disconnect thermocouple from circuit board
brass bushings in heatshield

8 – 10
SECTION 8 - DISASSEMBLY/REASSEMBLY

8.13 THERMOCOUPLE (3-550 PD)

TOOLS: bladed screwdriver
bracket phillips head screwdriver
1/4" nutdriver

Wraparound WARNING:
Front Panel Disconnect power from the wall outlet
8.12.10: Front panel must insert into offset bracket in before attempting to service the furnace!
wraparound
8.13.1: Follow steps 8.1.1 - 8.1.2 of control drawer removal
8.12.11: Check muffle resistance to verify wiring is correct
before securing control drawer:
100v 120v 200-240v
3-550 PD 8 ohms 8 ohms 24 ohms remove nut

8.13.2: Remove nut which holds thermocouple to

control drawer.

8.13.3: Disconnect thermocouple from circuit board

8 – 11
SECTION 8 - DISASSEMBLY/REASSEMBLY

8.14 POWER SWITCH

Remove 2 screws
TOOLS: Slotted screwdriver

8.14.1: Follow steps 8.1.1 through 8.1.2 of CONTROL DRAWER

REMOVAL

8.14.2: Disconnect switch wires

8.13.3: Remove the 2 screws which support rear panel.

8.14.3: Remove switch by pressing in tabs.

8.13.4: Remove screw used to secure thermocouple and

pull thermocouple from muffle. Pull thermocouple wire
through brass grommet.

8.13.5: Replace with new thermocouple by reversing previous

steps 8.11.1 thru 8.11.4

8.14.4: Press in new switch

8.14.5: Connect switch wires

8 – 12
 SECTION 8 - DISASSEMBLY/REASSEMBLY
8.15 POWER DOOR MOTOR REPLACEMENT 8.15.5: Disconnect wires (Female quick connect
terminals) from motor.
Disconnect wires
8.15.1: Slide control drawer forward using steps 8.1.1
and 8.1.2

8.15.2: Slide muffle assembly forward using steps

8.1.3, 8.9.4, 8.9.5 and 8.9.6 (approximately 5
inches).

8.15.3: Remove the 2 screws which support rear panel.

Remove 2 screws

8.15.6: Remove (4) screws to free motor

Remove 2 screws
Remove 2 screws

8.15.4: Remove the 2 screws to free motor linkage bracket

from base.
Remove 2 screws

8.15.7: Remove (4) screws and shoulder bolt to free

motor from motor bracket.

Remove 4 screws

Remove shoulder bolt

8.15.8: Replace with new motor by reversing previous

steps 8.15.1 thru 8.15.7.
8 – 13
PRODUCT SERVICE:
Three methods of product service are available:
• Telephone assistance available at the number listed below.
• Return the unit for servicing using the instructions below.

BEFORE RETURNING THE UNIT:

• Call DENTSPLY for a PR (Product Return) number. This is used to track and identify your unit. Equipment received
without this number may not be identifiable.
• If you do not have the original packaging, please request replacement packaging to ensure the unit is not
damaged in shipment.
• Secure top section in down position using original rubber bands supplied with the original packaging.
• Equipment damaged in shipment as a result of improper packing may not be paid by the carrier.

DENTSPLY will not be responsible for damages resulting from improper packing.

Ship prepaid to:

DENTSPLY Ceramco
ATTN: Equipment Repair
PR Number__________________
470 West College Ave.
York, PA 17404 USA
Phone: 800.835.6639 Option #1 (US Customers)
717.849.4502 (International Customers)
Fax: 909.795.5268
Email: equipmentrepair.ca@dentsply.com

Manufactured For: Distributed by:

DENTSPLY International Inc. DENTSPLY Canada
CERAMCO ®
DENTSPLY Ceramco 161 Vinyl Court
570 West College Ave. Woodbridge, Ontario
York, PA 17405-0872 L4L 4A3
1-800-243-1942 905-968-5374 Printed in U.S.A.
prosthetics.dentsply.com or dentsply.com 9363049 Rev. 12/11