Thermal Dynamics MERLIN 6000, Руководство по обслуживанию, Страница: 39 / 112

Manual 0-2569 33 SERVICE TROUBLESHOOTING
Driver PC Board
Rear of Front Panel
A-01083
Driver PC Board Location
On a X1 or X10 scale or with a digital meter set for diode,
measure between “C” (collector) terminal, wire #83, and
“E” (emitter) terminal, wire #84 (see NOTE). Reverse the
meter leads and measure again. It is normal to measure
an open (high reading) one way and a lower reading the
other. A low or zero measurement both ways means the
Q1 is shorted and must be replaced.
NOTE
Refer to Section 5.09-A for styles of transistors and
wire connection locations.
If correct, measure from the “B” (base) terminal, wire #82,
to “E” (emitter) terminal, wire #84. Normal reading is
from about 50 to 150 ohms (digital meter on ohms not
diode scale) a short (zero ohms) or an open indicates a
defective Q1.
NOTE
If the Switching Control Q1 has failed, the Driver
PC Board must also be replaced. Refer to Section
6.08, Item #2, for replacement parts.
The PWM compares shunt amp output on J9-5 with the
current control signal (3.3 - 10 vdc) from the remote (J7-
18) or the panel control (J10-15). A faulty shunt amp could
cause the output, normally 0 vdc with no cutting arc, to
go higher, shutting off the PWM and thus producing no
DC. If the shunt amp ribbon connector is disconnected
or pin 1 is open, approximately 12 vdc is applied to J9-5,
shutting down the PWM in the same manner as a shunt
amp failure.
The Switching Control PC Board sends pulses (+15 V) to
the Driver PC Board on J8-1 and J8-3. The width of these
pulses controls the on-time of Q1. The pulses are best
observed with an oscilloscope, but an AC voltmeter
should read about 6 to 7 VAC from J8-2 to both J8-1 and
J8-3. If 0 VAC is measured at both J8-1 and J8-3, with the
enables (J10-9 and J10-23) and shunt amp (J9-5) input low,
replace the Switching Control PC Board.
WARNING
Both base and emitter are at -320 vdc potential.
Use extreme caution when testing Driver PC Board
output.
If switching pulses are present at J8-1 and J8-3, check the
Driver PC Board output between J27-3, Q1 base, and J27-
2, Q1 emitter.
The Driver PC Board output, J27-3 (Q1 base) to J27-2 (Q1
emitter), should measure about 1 VAC. If voltage mea-
sures 0 to -4 vdc (+ lead on J27-3) replace Driver PC Board.
If switching pulses are not present (start signal OFF), -4
vdc is normal.
N. Main Contactor (W) Control Circuit
When the complaint is “Main Contactor doesn’t come
ON” or “Comes ON for a moment then goes OFF” what
to do?
There are a number fault sensors in the Power Supply
which can prevent the Main Contactor from coming ON
or cause it to shut OFF once it is ON.
The possible symptoms in this subsection are:
• Main Contactor (W) will not come ON at all
• Main Contactor (W) indicator is ON momentarily,
less then 1/2 second, then OFF.
• Main Contactor (W) on for 3 seconds then OFF;
No pilot.
• Pilot starts but Main Contactor (W) shuts off im-
mediately upon arc transfer.
• Main Contactor (W) goes OFF randomly during
the cut
• Loss of Start from the Remote Control
The symptom must be carefully considered to determine
where to look for the fault. Listed under each symptom
are a number of tests that need to be performed to insolate
the problem. Locate the symptom and proceed to that
symtom area.
Main Contactor (W) will not come ON at all
1. READY LED on Logic PC Board is OFF.
a. Unit over temperature, TEMP LED red, input
J1-9 will be greater than 7 volts.
b. Low coolant flow. Input at J1-5 will be high
(+15 vdc).