Bally 5000 Plus, Manual

Page: 303 / 388

C i r cu i t Descr i pt i on ( cont ' d )
The RX/TX por t ab l e boa r d r esponds
( W-1 299- 1 9 ) . Q7 t u r ns OFF . The
base of QS t u r n s ON w i t h t he
pos i t i ve vo l t age (VBB ) t h rough t he
b i as i ng r es i stor ( R 1 3 ) .
Then Q4
t u r n s OFF because of t he nega t i ve
vo l t age (VE E ) a t t he base o f Q4 .
Th i s causes t he base of Q6 to
t u r n
O F F w i t h t he pos i t i ve vo l t age (VBB )
t h rough R 1 1 and R 1 2 . VEE ou t pu t s
a t R X t h rough t he R 8 l i m i t i ng
res i stor . F rom t he so l de r j O i n t
( J 1 p i n
6 )
( W-1 299- 1 9 ) , R x goes to
t h e HHU t h r ough t he ma l e DB25
connector at p i n 2 .
Da t a Tr ansm i ss i on f rom t he HHU to
-- -- --
t he S l ot �ach l ne
The se r i a l da t a t r ansm i ss i on uses
pos i t i ve
( + ) and nega t i ve ( - )
vo l t ages . The + vo l t age I s a l og i c
LOW ; t he - vo l t age I s a l og i c H I GH .
Pos i t i ve vo l t age
The Tx s i gna l ( t r ansm i t t ed f rom t he
HHU )
I s a +5 VDC a t J 1 p i n 4 ( W-
1 299-1 9 ) . Th i s b i ases t he base of
Q1 ON caus i ng t he co l l ector of Q1
to be a l og i c LOW . Q3 t u r n s OFF
a l l ow i ng t he base of Q2 to b i as ON
t h roug h t he b i as i ng res i stor ( R9 ) .
The em i t t e r of t he CR3 em i t t e r
d i ode t ur ns O N em i t t i ng an I n f r a red
l i g h t sour ce . R 3 I s t he cur r ent
l i m i t i ng res i stor for CR 3 . The
I n f r a r ed l i g h t sou r ce l eaves t he
RX/TX por t ab l e boa r d .
The I n f r a r e d
I
I g h t sou r ce I s
opt i ca l l y r ece i ved a t Q7 on t he
RX/TX cab i ne t boa r d ( W-1 299- 1 8 ) of
t he mach i ne . The base of Q7 b i ases
ON caus i ng t he -1 2 V to t u r n OFF
t he Q5 t r ans i s tor . Then , Q4 b i ases
ON t h r ough t he R 1 4 b i as i ng
res i s tor .
1 1 . RX/TX BOARDS
NOTES
1 1 -7