Service manual

2. Rejumper the +18 volt block.

The lid of the power supply must be removed by taking out all the

relevant screws: four from the front panel, four from each side at the bottom of the unit, and three

from the back panel. The

voltage change-over jumper may now be moved to the appropriate

position. [see diagram]

3. Rejumper the -18 volt block.

This procedure is identical to the +18 volt block.

4. Selector, Phantom power module.

The voltage change over switch is located on the phantom power pcb, its setting is clearly marked

on the pcb.

5. Replace lid before reconnecting the mains supply.

Indicator Module. [Diagram XL293_2.DGM]

The pcb for this module (BRD:2690) is mounted behind the front

panel and houses led indicators for each of the P.S.U. output

voltages. Also mounted on this pcb is the ground lift switch S1.

This disconnects earth from the 0V rails. Earth remains connected

to all the console metalwork.

Regulator Assembly. [Diagram XL293_1.DGM]

This contains the linear regulators for both 18V supplies. Both negative and positive regulators

are identical utilising a series power fet (Q3 & Q6 respectively). Output voltages are factory set

at 18V with VR1 and VR4 respectively. D3 and D7 allow fail safe linking.

Phantom power supply. [Diagram XL293_2.DGM]

The 48V phantom supply is derived from transformer TX1, The primary supply voltage is se-

lected by SW1. The secondary voltage is rectified by D1 to D4 and requlated by IC1. The output

voltage being set by R1 and R2. D6 allows fail safe linking.

The power supplys cooling fans are also powered from the phantom power module. Two

alternatives types are catered for, 110V AC and 24V DC. When equipped for 110V AC fans,

connector ST2 is fitted. If 24V DC fans are used, the additional requlator IC2 with its associated

components and connector ST4 are fitted. Both types are not normally available simultaneously

on the same module. In the unlikely event of a replacement fan being required, the correct type

should be ascertained by checking on the pcb for ST2 (110V) or ST4 (24V).