IBM 3274 51C Maintenance Information page 55

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019
Map
A120
Power Ind. ON
or OFF
PAGE 5 OF 12
• Switch power off.
• At TSR power supply No.1. disconnect the two plugs P1 and
P2.
*G*
• After power was off wait 15 seconds and then switch power on.
I
At the disconnected power supply No.1. measure +5VDC at
jack J1 and J2 pin 2 (+) and pin 12 (-). See Figure 92.
Is the +SVDC still missing?
Y N
020
• Switch power off and reconnect disconnected power supply
No.1. plugs P1 and P2. *H*
(Entry Point C)
I
At logic board remove about half the cards as a group. *J*
I
After power was off wait 15 seconds and then switch power
on.
Did the power on indicator remain off?
Y N
021
I
Switch power off and reinstall the previously removed
group of cards. one at a time. and perform power on after
you install each card. Power on indicator should remain
off again when you install the failing card. Note: Do not
install cards when power is on.
Go To Map A100, Entry Point A.
022
• Switch power off and remove the remaining cards as a
group. *J*
I
After power was off wait 15 seconds and then switch power
on.
Did the power on indicator remain off?
Y N
8 6
J
K
3·28
023
I
Switch power off and reinstall the previously removed
group of cards one at a time. Power on indicator should
remain off again when you install the failing card. Note:
Do not install cards when power is on.
Go To Map Al00, Entry Point A.
MAP A120-5
*G*
Disconnect all loads from TSR supply and determine if overload is
causing +5V to be at OV.
*H*
TSR No. 1 is not causing power problem.
*J*
Determine if disconnecting this part or parts is causing the TSR
power supply to overload.

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