Service Manual

GSM-205-323
Power supply module (PSM)
31st Oct 01
Tech. 4–2
Technical Description: Horizon macro indoor
CONTROLLED INTRODUCTION
68P02902W07-B
Power supply module (PSM)
Types and
overview of
PSM
There are two types of dc power supply modules (PSMs):
 Nominal +27 V (negative earth input).
 Nominal –48 V (positive earth input).
There is one type of ac PSM:
 Nominal 120/240 V.
All PSMs have the same external appearance and are located in the same
positions. Different types are identified only by front panel labels.
The PSMs are fed from a backplane connector and use pulse width modulation
to generate output supply. A front panel switch (shown in Figure 4-2), disables
the output, reducing the input current as shown in Table 4-1.
Table 4-1 Input currents for power supply module
Type of PSM Output voltage
full load
Input current
full load
Input load
when output
switch off
+27 V nominal dc +27 V 32 A 1 A
–48 V nominal dc +27 V 18 A 0.5 A
120/240 V nominal ac +27 V 3.75 A 0.1 A
NOTE There are several manufacturers of the PSMs. Each is
fully compatible with the same type of PSM of a different
manufacturer.