74 - Display (G) Indicates Th = Igbt High Temperature; 99 - Display (G) Shows Off = Incorrect Mains Voltage Signal - Cebora SOUND MIG 2035/M Pulse Service Manual

CEBORA S.p.A.
− Make sure that the thermostat mounted on the diode group (56) is properly assembled and
functioning correctly; its contact must be closed at ambient temperature.
− Replace the control board (27).

3.4.16 - 74 - Display (G) indicates tH = igbt high temperature.

"tH" on display (G) indicates that power board (26) igbt temperature has risen beyond the
allowed limits.
With this alarm we recommend that you not shut off the power source, to keep the fan
running and thus cool the unit more rapidly. Normal operation is restored automatically as soon
as the temperature returns within the allowed limits.
If the alarm occurs repeatedly, we recommend that you:
− Make sure the fan (24) is operating correctly.
− Make sure that air flows smoothly, and there is no dust or other impediments to cooling in the
aeration tunnels.
− Make sure that the working conditions comply with the specified values, especially observing
the "duty cycle".
− Check the wiring between terminals 1 and 2 on J3 control board (27), and terminals 1 and 2
on J6 power board (26) (igbt temperature signal). This signal is PWM type, with duty cycle
proportionate to the temperature, and thus difficult to check.
− Check the supply voltage to the IGBT temperature measurement circuit = 5 Vdc, measured on
the terminals of the zener diode Z2 on power board (26). If incorrect, check the wiring
between J1 power board (26) and J1 power supply board (25). If incorrect, with power source
off, temporarily disconnect J1 on power supply board (25) and check the resistance between
the terminals of the patch connector disconnected from J1. Correct value = junction of one
diode in one direction and >Mohm with the probes reversed. If incorrect replace the power
board (26), and check the voltage again at the ends of Z2. If incorrect, also replace power
supply board (25).
− Replace the control board (27).

3.4.17 - 99 - Display (G) shows OFF = incorrect mains voltage signal.

This signal normally appears whenever the power source is shut off.
When mains voltage is missing, for example after opening the switch (16), the control circuit
remains powered for a few seconds due to the effects of the DC-capacitor discharge on the
power board (26); at such times it orders the power source to stop, with "OFF" signal, as it
detects the missing mains voltage.
If this signal is present with switch (16) closed and mains voltage present, carry out the
following test.
MAINS VOLTAGE PRESENCE SIGNAL TEST.
Control board (27), connector J11, terminal 1 and 2 (gnd) = fig. 5.2.5, with power source
powered.
♦ Check the wiring between connectors J3 power board (26) and J11 control board
(27).
♦ Make sure 230 Vac mains voltage is present at terminals TP1 and TP2 of power
board (26).
♦ Replace the power board (26).
♦ Replace the control board (27).
3.302.161
Correct?
YES
NO
31
24/03/2004