Bose 1801 Service Manual download pdf (Page 24)

23

TROUBLESHOOTING GUIDE

SYMPTOM POSSIBLE CAUSE

1. DC Offset:

≤2v Defective U1

Defective Q1

≥2v Defective U1

Defective CR1, 2, 6, 15

Open ground at the RCA

input jack

Test point "A" polarity

the same as DC offset

(see Figure 11)

Defective Q1-8, Q24

Defective CR16, 17

Test point "A" polarity

opposite to the DC offset

(see Figure 11)

2. High Current: Short between transistor

and heat coupler

Shorted driver or output

transistor

Trouble shoot (by removing

collector screws) in this

sequence.

Negative: Q9, 11, 23, 21,

22, 19, 20, 18

Positive: Q6, 10, 17, 16,

14, 13, 12, 15

3. Oscillation:

Unloaded Defective C5

Defective Q6, Q9

Defective CR8

Loaded Open C4, 5, 9, 11

Defective R24, 29, 30,

51, 52

4. Excessive Noise: Defective U1, Q1

Defective R57, 58

5. No Bias Adjustment: Defective Q4, 6, 7, 9

Open R11, 12, 13

6. Incorrect Frequency

Response: Defective C5, C8

Shorted Mica Insulator Q3

7. Excessive Distortion: Defective Q7, Q8, Q25

Defective CR18, 19

Defective CR5 ( at full

output only)

1 2 ... 19 20 21 22 23 24 25 26 27 28 29 30 31 32

Comments to this Manuals

No comments