Memotech Limited MTX 500, Service Manual

Page: 33 / 78

29
Repair Method
1 If pulse is absent on 4Mhz Xtal - follow
associated circuitry until fault is apparent.
2 If RESET is held low-
follow associated circuitry until fault is
apparent.
Also - see page 33.
d)
Cause of Trouble
Blank screen with no control G sound
Check Point
If above checks are o.k. check the 10.6875 ;hz
Xtal
Repair Method
1 If pulse is absent Xtal is likely to be faulty.
2 If pulse is present the TMS 9929 video
processor is faulty.
NB: Before these tests are carried out, try switching
the power on and off a few times to establish whether
or not the problem is merely a fire up fault. See ref
page 47 for timing modification.
MTX Service Manual