SEO Version
Display Driver Board
The Display Driver Board operates the Dual (Williams) or Single (Bally) display boards. This
board drives a maximum or two 16-digit alphanumeric displays. It provides the ±90V needed to
power the display glasses and the UDN-6US and UDN-71BOchips.
There are three versions of the Display Driver Board; A-12739-1 (no extended displays), A-12739 -2
(one extended display) and, A-12739-3 (two extended displays). The version you have de termi nes
which UDN-71BOchips, UDN-6US chips and resistors are installe d.
Digit Circuits (Ul, U2, U3, U4, U5, U6, U7, U8,
um
The digit circuits enable specific digits on the display glasses .
The microprocessor sends a signal to U16 a 74LS734 data latc h, which in turn sends a signal to Ull
a 74LS139. The data is then sent to another set oflatches U6 and U7, both are 74LS240. From U6 and
U7 the signal branches out to
VI,
U2,
V3,
U4 ,U5 and ,
VB.
These chips are the
VDN-6118s
and they
provide the voltage level shifting. The output of the UDN
-611B
chips goes directly to the proper
display glass . When a digit is enabled the output at the pin of the UDN-6118 that drives the digit is
abou t+90V.
Segment Circui ts (U9, UI0, U12 , U13, U14, U15)
The segment circuits enab le specific segments within a digit on the display glasses.
The microprocessor send a signal to U14 and U15, which are 74LS374 data latches. From
V14
and
U15 the signals goes directly to the UON-7lBOchips, U9, U19, U12,
V13.
The UDN-71BOprovides the
voltage level shifting. When a segment is enabled the output at the pin of the UDN-71BOthat drives
the segment is about -90Y
Power Circuit
The Display Driver Board provides the ±90V for the disp lay glasses,VON -6118and, UDN-71BO
chips. J307 is the input from the transformer secondary. After F30 1 the circuit branches into two
smaller circuits. One for the +90V and one for the -90V. The cathode ofD4 is +H3V, the anode of D3
is -U3V. The collector ofQ2 is +94Vwhi le the collector ofQl is -94V. The final output for the +90V
circuit is the emitter of Q4 which is +95V. The final output for the -90V circuit is the emitter of Q3
whic h is -95V. These are approximate voltages and have a tolerance of± 5Y
Single
and Dual Display Boards
The Single and Dual Display Boards contain the 16-digit alphanumeric glasses. As implied by
the name the Single Display Board contains one glass, while the Dual Display Board Contains two
glasses. For Bally games, two Single Display Boards are used side-by side . They are located on
the insert panel. For Williams games, one Dual Display Board is used and it is located on the
speake r panel.
These boards obtain data from the Display Dr iver Board through ribbon cables.
Powered by FlippingBook Publisher