Panasonic JB-3300 Technical Manual page 463

(3)
Controller select
(a)
(b)
1)
2)
(c)
1)
The controller hardware status is not in the command request
mode after the controller has been selected.
Oo Address comparator 74LS682 (3E) or decoder 74LS138 (5H) is
faulty.
Oo HOST I/F NDC 843 (1B) or NDC841 (1A) is faulty.
o MPU Z-80 (6E) is faulty.
Oo some of the MPU peripherals (74LS32 (5F), 74LS244 (6F),
74LS00 (8G), 74LS74 (4C), ROM (6C), or RAM (7C)) is faulty.
DRO does not rise even after one byte of command has been
sent;
NDC 840 (4B) Pin 1 is on the HIGH level.
o NDC 843 (1B) or NDC 841 (1A) is faulty.
NDC 840 (4B) Pin 1 is on the LOW level.
o NDC 840 (4B) is faulty.
oO Some of MPU peripheral ICs is faulty.
Does not start even after the command has been transferred;
NDC 840 (4B) Pin 1 is left on the HIGH level.
o NDC 840 is faulty.
o NDC 843 (1B) or NDC 841 (1A) is faulty.
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