Panasonic JB-3300 Technical Manual page 464

(4) READ mode
(a) End IRQ does not rise even after the command has been
transferred.
o HOST I/F NDC 843 (1B) or NDC 841 (1A) is faulty.
o NDC 840 (4B) is faulty (DMA).
(b) Always an error occurs after start.
o TL 497 (2H) is faulty.
o TL497 peripheral circuit is faulty.
2) Check if the output from NBC 847 (4H) Pin 8 is +0.5 v +2.0 V.
o NDC 847 (4H) is faulty.
3) Check the READ data from the disk.
o NDC 842 (7E) is faulty.
Oo NDC 840 (4B) is faulty.
o NDC 846 (4A) is faulty.
Oo 74L8123 (7G) is faulty.
(c)
Some times an error occurs after the start.
1) Refer to (b) 1).
2) 74LS8123 (7G) Pin 12
o Confirm the LOW level and 260 ns +30 ns.
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