BOSE 1401 Schematic

BOSE 1401 DIRECT/REFLECTING® MUSIC SYSTEM

TROUBLE SHOOTING GUIDE

Refer to the Bose 1401 Service Manuals, part numbers 116684 and 122762, for schematics, PCB layouts and part list. Unit identification: 1401 series I has a silver face plate. 1401 series II has a black face plate.

Symptom Check

Draws current: Check D55, series II; Check D2, series I No left or right output: Check electrolytic caps at the input to U51 or at the output

of U52 for series I and U53 for series II. Replace all caps

with a silver colored can. Spatial not working: Check C88, C87 series II, C65, C85 series I Drivers running hot: Check the bias diodes D11, 12, 21, 22, 31, 32, 41 and 42. No output one channel only or unit

cycles on and off:

Unit will not turn on: 1: Outputs should not be grounded. Isolate test

No output or cycles on and off after installing new outputs and drivers:

No low frequencies: Check U53

1: Check output and drivers; Replace both outputs, both

drivers and both bias diodes, if one is found defective.

Check the 27Ω resistors connected to bias diodes.

2: Check Q54 and Q55 for series II.

equipment from ground.

2: Check Q62, Q63, U52 for series II. Check Q51, Q54,

U50 for series I.

3: Check D51, R120, Q53. Make sure the remote turn on

violet wire is connected to power, series II.

Check for cracked screw insulators and make sure that the

insulator between transistors and heat sink is good.

1997 Bose Corporation Part Number 122762-TG1

06/97 Rev00