Bally 5000 Plus, Manual

Page: 302 / 388

1 1 . RX/TX BOARD S
C i r cu i t Descr i pt i on ( cont ' d )
Da t a T r a n sm i ss i on f r om S l o t M a c h i ne
-- --
t o HHU
The ser i a l d a t a t r ansm i ss i on uses
pos i t i ve ( + ) and nega t i ve ( - )
vo l t ages . T h e + vo l t ag e 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 T x s i gna l ( t r ansm i t t e d f r om t he
mach I ne ) I s a + 1 2 VDC a t J 1 p i n 4
( W- 1 299-1 8 ) . T h i s b i ases t he b a s e
of Q 1 ON caus i ng t he co l l ec t o r o f
Q 1 t o be a l og i c LOW .
Q3 t u r ns O F F
a l l ow i ng t he b a s e o f Q2 t o b i a s O N
t h r ough t he b i a s i ng r e s i s t o r ( R9 ) .
T h e em i t t e r o f t he CR3 em i t t e r
d i ode t u r ns O N em i t t i ng a n I n f r a r e d
l i g h t sou r ce . R 3 i s t he cur r e n t
l i m i t i ng r e s i s to r f o r CR3 . T h e
I n f r a r ed l i g h t sou r ce l eaves t he
cab i ne t .
The I n f r a r ed l i g h t sou r ce I s
opt i ca l l y r ece i ve d a t Q7 on t he
RX/TX por t ab l e boa r d ( W- 1 299- 1 9 ) o f
t he HHU . T h e base o f Q7 b i a s e s ON
caus i ng t he nega t i ve vo l t age ( VE E )
to t u r n O F F t he Q5 t r an s i s t o r .
Then , Q4 b i a s e s ON t h r ough t he R 1 4
b i as i ng r e s i s t o r . T h e base o f Q6
b i ases ON w i t h t he VEE t h r oug h Q4
and t h e b i a s i ng r e s i s to r ( R 1 2 ) .
V88 ou t pu t s a t R x t h r ough t he R 8
l i m i t i ng r e s i s to r . F r om t he so l der
j o i n t ( J 1 p i n 6) ( W- 1 299- 1 9 ) , R x
goes t o t he HHU t h r ough t h e ma l e
D825 connec t o r a t p i n 3 .
Nega t i ve vo l t age
The T x s i gna l ( t r an sm i t t ed f r om t he
mach i ne )
i s a - 1 2 VDC a t J 1 p i n 4
( W- 1 299- 1 8 ) . T h i s b i a s e s t he b a se
o f Q 1 O F F . T h e b a s e o f Q3 b i a s e s
O N t h r ough R 6 . Q3 s e n d s a l og i c
LOW to t he b a s e o f Q2 t u r n i ng Q 2
O F F . T h e n C R 3 t u r ns O F F a n d
t r ansm i t s n o l i g h t .
1 1 -6
NOT E S