Service manual

Dual PSU (redundant) Assembly

Setup Procedure

Ensure that no cards are plugged in. Remove the "LINK FOR PSU3" jumper on the

monitor board.

Check that there are no short circuits between any of the diode terminals and 0v or

chassis. Also check that the diode's mounting plate is isolated from the chassis. Check

that all the power wiring to the backplanes and the disk-drive is correct.

Disconnect the current-share link between the PSUs. Apply power to PSU1 and set the

5v rail to 5.4v and the 12v rail to 12.4v, when measured at the PSU terminals (i.e.

before the diodes).

Remove power from PSU1 and repeat step 3 with PSU2.

Remove power and plug in all cards.

Connect the current-share link between the PSUs and apply power to PSU1. Set the

voltages to 5.05v * 50mv and 12v * 100mv, when measured at the backplane (i.e.

after the diodes).

Remove power from PSU1 and repeat step 6 with PSU2.

Apply power to both PSUs and check that the voltages are as set in step 6. If

adjustment is required then ensure that both pots. for that rail are trimmed by the

same amount in order to maintain the load sharing (N.B. the voltage reading will not

be valid until the second pot. has been trimmed, so make only small, equal

adjustments).

PSU Monitoring

Check that the PSU1 and PSU2 green LEDs on the monitor board are lit and that the

front panel LED is on. Also, check that pins1&6(PSU1) and2&7(PSU2) of the

9-way, D-type connector are short circuit.

Remove power from PSU1 and check that the corresponding LED extinguishes and

the front panel LED flashes roughly twice a second. Also, check that the

corresponding pins of the D-type connector are open circuit.

Re-apply power to PSU1 and repeat step 2 with PSU2. Re-apply power to PSU2 when

finished.

Check each voltage monitor wire from the two PSUs by removing each in turn from

the monitor board and checking that the corresponding LED for that PSU

extinguishes.

Digital Service Manual

Issue 3 Page 66