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Lamp Circuit
1. None of the Lamp Matrix (oontrolled) lamps work.
Check LED 6 on the power driver board. If it is Off check F114 and BRI. If it is On check U9 and
UIS. Both chips should have high pulsed on the outputs . Be sure the +lSV wire is not broken. In
rare cases the transformer wind ing for the
+
ISV can fail ,
2. Alamp row is either
very
bright
or dead.
The TIPI02 is most likely to cause this problem. The LM339 comparato r is the next component to
check . Occasionally, the 74LS74 can cause a problem.
Hint :
A
fast way to tell if the TIPI02 transistor is defective is to ground the tab of the transistor.
If
you ground the tab and noth ing happens the transistor is probably good. If you ground the tab and
the row lights, the transistor is probably defective.
3. A lamp column stays
On
all the
time.
Most likely its the TIPI07.
4. A lamp row stays On all the
time.
Most likely its the TIPI02 .
5.A few unrelated
bulbs
never turn On.
Check the bulbs and the sockets . Be sure the column and row wires are soldered to the socket.
6. All of the lamps stay On and never turn Off.
Most likely U9 is defective but, UIS could have fa iled at the same time .
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