Tait TM8100 mobiles, Service Manual

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TM8100/TM8200 Service Manual Fault Finding of Control Head with Graphical Display 439
© Tait Electronics Limited November 2007
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