Bose 1800 Service-Handbuch - Seite 24

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S Y M P T O M

1. DC Offset:

2. High Current:

3. Oscillation:

Unloaded

Loaded

4. Excessive Noise:

5. No Bias Adjustment:

6. Incorrect Frequency

Response:

7. Excessive Distortion: Defective Q7, Q8, Q25

TROUBLESHOOTING GUIDE

≤2v

Defective U1

Defective Q1

≥2v

Defective U1

Defective CR1, 2, 6, 15

Open ground at the RCA

input jack

Defective Q1-8, Q24

Defective CR16, 17

Short between transistor

and heat coupler

Shorted driver or output

transistor

Defective C5

Defective Q6, Q9

Defective CR8

Open C4, 5, 9, 11

Defective R24, 29, 30,

51, 52

Defective U1, Q1

Defective R57, 58

Defective Q4, 6, 7, 9

Open R11, 12, 13

Defective C5, C8

Shorted Mica Insulator Q3

Defective CR18, 19

Defective CR5 ( at full

output only)

POSSIBLE CAUSE

Test point "A" polarity

the same as DC offset

(see Figure 11)

Test point "A" polarity

opposite to the DC offset

(see Figure 11)

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