Thermal Dynamics MERLIN 6000, Руководство по обслуживанию, Страница: 33 / 112

Manual 0-2569 27 SERVICE TROUBLESHOOTING
b. Check for about 220VAC between wires #86 and
#87 on Motor Contactor, MC3.
• If voltage is correct, then the Pump Motor is
faulty.
• If voltage is incorrect, then the Motor Contactor
is faulty.
c. Check for 14 vdc from the Logic PCB, TP1 (ground)
to J4-8.
• If voltage is correct, Logic PCB is faulty.
• If voltage is incorrect, then proceed to step d.
d. Check for 14 to 18 VAC incoming power to the
Logic PCB by measuring from TP1 to J1-2 and TP1
to J1-3.
• If voltage is correct, then proceed to step e.
• If voltage is incorrect, refer to Section 4.05-A
28VAC Test.
e. Check for 2 to 3 vdc from TP1 to J4-8.
• If voltage is zero there is an open connection
between the Logic PCB and MC3.
• If voltage is 14 to 15 vdc proceed to step f.
f. The Logic PCB may be faulty or it is not detecting
that it is a Master Power Supply. Check for about
15 vdc from TP1 to J4-9 if this is a Master Power
Supply.
• If the voltage is about 15 vdc the Logic PCB is
faulty.
• If the voltage is low, there is a short in the wir-
ing or the remote cable so that J15-35 and J15-
36 (see NOTE) are connected.
NOTE
In the Slave Power Supply, the Parallel Cable has
a jumper that connects these two pins intention-
ally to shut OFF the Pump.
E. Diode Check
There are fourteen diodes in the main heatsink area,
including six large 150 amp input rectifier diodes (D1-
6) and eight small 70 amp diodes (snubbing diodes
D7-10 and freewheeling diodes D11-14). To measure
the resistance of each diode use one of the following:
• An ohmeter set on the Rx1 or Rx10 scale
• Digital meter set to the diode function
Measure the resistance of each diode in both direc-
tions. The readings should differ by at least a factor
of ten. If the readings do not differ (both high or both
low), disconnect one end of the diode and recheck. If
the diode reading is not correct with one end discon-
nected, then replace the diode. Check all diodes be-
fore turning on power to the system.
If a diode fails, check the potential causes of diode
failure to make sure the replacement diode will not
also fail when it is installed:
1. Isolate and check each diode separately to deter-
mine which individual diode has failed.
2. High frequency protection for the input rectifier
diodes (D1-6) is provided by capacitors C1 - C6
and MOV 1-3, which are located between each side
of the diode heatsink on the input filter PC board.
Except for the shorts, these components can not
be checked with a volt/ohm meter. To be safe, the
complete input filter board should be replaced any
time an input diode fails.
3. Diodes can overheat if air flow over the heatsink is
not adequate or if the diode is not properly fas-
tened to the heatsink. Check that all small diodes
(D7-14) are torqued to 20-25 in-lbs (2.3-2.8 Nm)
and all large diodes (D1-6) are torqued to 34 in-lbs
(3.8 Nm). Apply a light film of electrically con-
ductive heatsink compound between the diode
and heatsink. Make sure air passages in and out
of the unit are not obstructed.
4. Diodes that are faulty at the time of manufacture
are difficult to diagnose. These diodes generally
fail within the first few hours of operation. Before
deciding that this was the case, be sure to check
out other possibilities.
F. Thermal Sensing Circuit Check
1. Thermal sensors TS1, TS2, TS3, TS4, and TS5 are
connected in series to J1-9 on the Logic PC Board.
TS2 is a PTC resistor whose resistance varies with
temperature from about 100 ohms at room tem-
perature (68°F/20°C) to 3.3K at 140°F (60°C) switch
point. TS1, TS3, TS4 and TS5 are switches nor-
mally closed, 0 ohms, that open at over tempera-
ture. TS1, TS4 and TS5 are part of the Main Trans-
former Assembly. TS2 is on the Heatsink and TS3
is on the Pilot Resistor.
Check the voltage from J1-9 to test point TP1 (or
J1-8) on the Logic PC Board for less than 7.5 vdc.
If the voltage is greater than 7.5 vdc, the unit is
overheated or a temperature sensor is faulty.
2. If the unit still operates but the TEMP indicator is
red, the problem may be on the LED PC board. If
the voltage is less than 7.5 vdc, check the voltage
from J3-4 to test point TP1 (ground). If the voltage