TM9100 Service Manual Fault Finding of Control Head 413
© Tait Electronics Limited August 2005
Several Keys Faulty
The keys can be grouped into columns and rows of three or two keys, as
illustrated in Figure 14.11.
If one column of keys is faulty:
1. Visually inspect the associated resistor and diodes for open or shorted
circuits.
If one row of keys is faulty:
1. Visually inspect the associated resistor for open or shorted circuits.
F2 key
F4 key
scroll-up key
R620
D602
F1 key
right selection key
scroll-down key
R621
D620
F3 key
left selection key
R622
D604
F3 key
F4 key
right selection key
R623 scroll-up key
scroll-down key
left selection key
R624 F1 key
F2 key
R625
Figure 14.12 PCB layout of the function, scroll, and selection key circuitry
top side
bottom side
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