Play Meter

3 8 TECHNICAL TOPICS TOPICS TECHNICAL BY Randy Randy Fromm Fromm BY . I.I. . . Atari's steerin steeringg board board Atari's To date, date, Atari Atari Inc. Inc. has has produced produced To an even dozen driving games. With an even dozen driving games. With the exception exception of of the the earliest earliest of of these these the the same same games, Atari Atari has has used used the games, steering board throughout. This has steering board throughout. This has cut development and tooling costs cut development and tooling costs for the the manufacturer manufacturer while while giving giving for of having operators the advantage operators the advantage of having aa variety of of games games with with aa common common variety replaceable module. replaceable module. This isis good good news, news, because because itit This reduces the number of replacement reduces the number of replacement parts needed needed to to service service aa route route or or parts arcade. If the service man carries arcade. If the service man carries aa spare board board with with him, him, he he can can fix fix spare steering problems in everything steering problems in everything from Trac Trac 10 10 to to Sprint Sprint 8. 8. from It all sounds simple, right? Ahhh, It all sounds simple, right? Ahhh, but there's there's aa catch catch to to everything everything but and you you certainly certainly can't can't expect expect this this and to be any different. It seems as to be any different. It seems as though a steering board is somethough a steering board is somelike aa Japanese Japanese transistor transistor thing like thing radio. It ends up costing just about radio. It ends up costing just about as much to h~ve it repaired as itit as much to have it repaired as does to to buy buy aa new new one. one. I I know know of of does few operators operators that that don't don't have have at at few least a couple of dead steering least a couple of dead steering lying around around somewhere. somewhere. boards lying boards easily repaired repaired These boards boards can can be be easily These and the the fix fix will will often often take take less less than than and five minutes and cost less than one five minutes and cost less than one dollar. dollar. repairisis considerably considerablyeasier easier Since repair Since when· you you know know how how aa circuit circuit is is when supposed to operate, let's take supposed to operate, let's take aa look at at the the block block diagram diagram in in figure figure 11 look and the the schematic schematic in in figure figure 2. 2. and Notice that that the the steering steering board board is is Notice two identical channels. divided into divided into two identical channels. This makes makes things things easier easier right right from from This the start. In testing the board we the start. In testing the board we can compare compare one one channel channel to to the the can other and and isolate isolatethe the bad bad side. side. This This other will automatically eliminate half of will automatically eliminate half of the components as being defective. the components as being defective. Each half half of of the the steering steering board board acts acts Each independently from the other and independently from the other and sends its its own own signal signal to to the the logic logic sends board. board. The steering steering board board works works in ih the the The way that that the the "electric "electric eye" eye" same way same announces your entry into the announces your entry into the liquor store. The neighborhood neighborhood liquor store. The Light Emitting Emitting Diode Diode (CR1) (CR1) isis an an Light infrared light source. This LED infrared light source. This LED emits an an extremely extremely narrow narrow beam beam of of emits monochromatic light light into into aa PhotoPhotomonochromatic Darlington transistor transistor (Q1). (01). This This Darlington transistor acts as a receiver whose transistor acts as a receiver whose output isis inverted inverted and and amplified amplified by by output CHANNEL A A CHANNEL ~i CHANNEL B B CHANNEL E]i LED CR1 LED CR 22 the output output transistor transistor (Q2). (02). When When the the LED LED isis allowed allowed to to shine shine on on the the the 01 "sees" "sees" the the photo-transistor, Q1 photo-transistor, infra-red beam beam and and turns turns itself itself on. on. infra-red This also causes 02 to begin This also causes 02 to begin conducting and and the the output output goes goes to to conducting ground. ground. slotted wheel wheel of of the the When the the slotted When steering unit unit interrupts interrupts the the beam beam steering between the the LED LED and and the the photophotobetween 01 and and 02 02 are are both both transistor, Q1 transistor, turned "off" "off" or or not not conducting. conducting. turned Thisputs putsaahigh highat atthe the output. output. The The This PHOTO PHOTO XISTR XISTR 01 Q1 PHOTO PHOTO XISTR XISTR 03 Q3 - AMP AMP XISTR XISTR 02 Q2 - AMP AMP XISTR XISTR OUTPUTA A OUTPUT - -0 - OUTPUTB B OUTPUT -- 04 Q4 FIGURE1 FIGURE1 •5 VDC VDC +5 R1 75 Q1 R2 R3 470 470 O C1 OUTPUT .1 R6 Q2 2.2K CR 11 CR FIGURE 22 FIGURE GND. O GND.