IBM 3274 51C Maintenance Information page 52

Map A120 Power Ind. ON
orOFF
PAGE 2 OF 12
(Step 001 continued)
zero. The MAP concept is to verify that the primary input D.C.
voltage to the TSR is correct. If incorrect, the filter capacitor,
diode assembly, power transformer cables, etc. are measured for
proper voltages. If input voltage is correct to TSR, all the voltage
loads are disconnected from TSR supply. The +5 voltage is
measured at TSR and if good, loads are reconnected and then
disconnected one at a time until the power on indicator turns on,
which then isolates the failing part.
NOTE: When power is off and a short or overload condition is
disconnected from the TSR supply, a time period of 15 seconds is
needed before switching power on. If this is not done the TSR
voltages will not reach their proper level. This same condition
also occurs if all TSR loads are disconnected (plugs P1 and P2
disconnected).
CAUTION
Before removing cards or cables switch power off.
DANGER
Input AC voltage is present on prime power box plug Pl, and
ON-OFF switch when power is off.
Is the 3274 fan turning? *A*
Y N
002
Is the power on indicator lighted?
YN
003
• Input power problem.
Go To Map A122, Entry Point A.
004
• Switch power off and disconnect power cord plug.
• Verify plug connection at fan assembly. See Figure 4-6.
• For U.S. and Canada machines: Measure for input A.C.
voltage at prime power box plug P5 between pins 1 and 3. If
missing, verify plug and socket connection. See Figure B-1.
• For World Trade machines: Measure the fan AC. input
voltage at power transformer terminal block. See Figure B-6
for voltage and terminal pins .
• Replace fan.
Go To Map A100, Entry Point A.
MAPA120-2
-A-
If fan is turning this indicates AC line vcltage is applied to prime
power box jack J3 and J5. Plug P3 goes to power transformer
input.
Chapter 3. Maintenance Analysis Procedures 3·25