HEIDENHAIN TNC 306 Service Manual - Manual (Page 36)

SERVICE MANUAL TNC 306/360
Page 32
HEIDENHAIN Service
8.4 Checking the Power Supply (Power Supply Unit)
Two low-voltage fuses are located on the "POWER SUPPLY" assembly. The fuse F 2.5A
protects the output voltage of +24V BE (not used with TNC 306/360) and the fuse F 4.0A
protects the remaining voltages (see block diagram, sec. 8.3.1). If an error occurs in the
power supply (all voltages are missing), first check the +24V at the supply line (2-pin
terminal block X31) and then the low-voltage fuse F4.0A.
By means of the TEST LOAD unit, the power supply can be checked fast and easily. For
this purpose the connector X21) leading to the processor board must be disconnected from
the power supply and connected to the TEST LOAD unit.
The different values can be measured at the sockets of the TEST LOAD unit with a
multimeter. The values and their tolerances can be seen from the table in section 8.3.2.
If no TEST LOAD unit is available, the voltages can be measured at the measuring points on
the processor board (see sec. 8.4.3).
The values and their tolerances can be seen from the corresponding tables. If the
measured values deviate distinctly from the values in the table, the "power supply"
assembly is defective.
*
Attention!
Always switch off the main switch when engaging or disengaging any
connectors.
The power supply unit does not function during free run.
(basic load is required)
1) If you are using power supply units without connectors, no TEST LOAD unit can
be used. In this case, the voltages can be measured on the processor board
(see sec. 8.4.3) or on the power supply board (see sec. 8.4.2).