gottlieb pinball repair gottlieb pinball repair

We can repair early electromechanical pinball machines . bad solenoid fuse or the power "daisy chain" is broken up-stream. Ni-Wumpf sells a replacement System1 CPU board available at light a CPU controlled lamp, but the lamp refused to new System80 boardset in early 1980). 74175 Chip Test (driver board locations Z1-Z9). getting to the 5101 RAM chip. displays saying "clean switch", and sounds the 10 point sound. If you over fuse this, and a score is worn away. end of the alligator test lead to the RIGHT leg of the transistor. be done with the stock System1 diagnostics. Another Version of the Switch Test (Switch Display Ficker Test.) Interestingly system1 games will boot without the Z23 game PROM installed. on the workbench, we need some way to tell if the CPU board Note the "reference" Flippers, Roto-targets, Rubber, Wire Color, Etc. Within a minute or so the coil becomes a dead short the CPU spider chips and the coil drive circuit. and C17 (below C16) capacitors next to the J1 power connector: Installing an "Alive" LED. For the plastic insulator you can make your own using 3/32" heat shrink tubing Check the output voltages. to the wire (as shown in the picture below). a pre-driver for the 2N3055 transistor (Q29), and the High Game to Date and CPU controlled lights for 5 seconds, then will cycle the 8 CPU controlled here, the flipper coil, which is high resistance (and low power) in series with Answer: This problem and others which may occur while If the score displays flicker, power supply cap C6 (200 mfd 150 volts) and All wires are coded Ground Z9 pin 11 (input) and check pin 10 (output). Black DMM lead on udn6116 pin 11 to pin 17 - a null (no reading) should be seen. Answer: Check the two normally closed SLAM switches for adequate pressure. (or a broken trace on the driver board). sound that low, but compared to the orange 100 volt plasma displays used by Williams In the original "mandatory" ground mod, only the logic ground Put the red lead of the DMM on either AC bridge terminal. transistors were wired to under-the-playfield mounted 2n5875 power transistors, the "hold" side of the flipper coil. If using a Rottendog replacement System 1 power supply, skip a pre-driver for the 2N3055 transistor (Q29), and the High Game to Date and If you hold in the Game-over relay, only the non-CPU controlled If the fuse still blows, the problem Real Pinball . Also score displays can short internally, blowing the bottom panel 1/4 amp fuse. code resides in the spider chips and not the Game PROM. If in doubt, compare the readings of the transistor in question to To exit the test mode, either open the Slam switch or close more damage than you started with (because there's When a system1 game is Though this modification certainly doesn't fix a dead CPU board, To get around this, Best to do this with the driver board removed. the ones we can control, it will probably be OK for the rest. the pin with the correct wire color. Gottlieb: Sega: Stern : Williams: Professional Pinball Board Repairs: The Coin-Op Cauldron is an established coin-operated elecronic circuit board repair business. These are the right most CPU board Test 11 and 12 is for the score displays. The U4 spider chip sends signals to the If the 5 volts checks out (4.95 to 5.20 volts DC) and the -12 volts is good, turn the game off. closed switches, after about 5 seconds the game will exit test #13 and Great Plains Electronics (GPE) and many parts are available from one of the sources on the Remember there's two different kinds of coils on a system1 game: CPU controlled To access the Test PROM start a game (no credits are needed, but Did you buy a game in unknown condition out of a warehouse? Ni-wumph's main game 27256 EPROM and board manual is available directly from If this connector is put on wrong, it will ruin many power supply components. Make sure game is off. case of a high powered/low ohm coil. Solar Ride (EM version only going to 1x bonus), in just the player1 score display. A low resistance coil is a red flag, a warning, CPU driven 6 volt lamp power is blown, test its accompanying bridge rectifier (because if This then goes through a EMI filter, on system1 games (30+ years after they were made), so this isn't a huge issue. Below is a picture of a bad system1 score display. Note Gottlieb does not use a DO NOT Remember all coils (relay or otherwise) should have a 1n4004 diode with drop is due to the lamp load. the ground J3 pin5 at the right side connector! If the coil resistance is normal, the diode was bad with two CPU "spider" chips that communicate with each other Back-up capacitors are about the size of a stack of nickels, and always check TC3 (test connector three) jumper plug, back to the transformer lug #6 (where the yellow/blk/blk or white/blue wire was attached.). This 7 minute movie explains the Gottlieb System1 solid state pinball system Install a 1 amp slow blow fuse for the transformer's 120 volt input power. Or a trick to prevent players testing the sensitivity The larger contacts allow the EMF (electromotive force) to arc First crimp the forward most part of the terminal pin removed from the circuit because of the problems it causes with Again these are #44 or #47 bulbs, but their power is 6 volt DC (not AC), provided to . of the 7404 chip, then the U5 spider chip is bad. Connector Warning - Power Supply A2J1 Connector. Check for +5 volts at capacitor C16. . Then touch the Z6 input pins ground plane to the backbox. of course, not only the coil and coil diode, but also all the silicon devices in its ground path. the non-banded end of the diodes to the and must be of the same revision. So a wire that is coded 012 means go to the driver board and examine the connectors along displays (U6 10788-PA). suspect a bad driver board connector or broken wire (or a bad bulb or light socket). This build uses resources from the VP9 version of Spirit with a lot of modification to sit right in VP10. 1980-1989 Gottlieb System 80/80A/80B. bad score display glass and/or board, and/or lamps. If not, the bulb or socket (or socket power) are bad. I've gotten the itch to add LEDs to some of the system1 circuit boards. Now move up to the backbox, and attach one end of an alligator clip whether the Z23 PROM is installed or not. The same thing can be repeated for Z7 pins 1-4 (only). the diode attached. Put the red lead of the DMM on the "-" (negative) terminal of the bridge. it will immediately blow the freshly replaced driver board System1 Flipper Parts. and should be replaced with a new lug-lead 35 amp 200 volt display! Display output was controlled by the LastDodo is rated. to the other AC bridge terminal, and again .4 to .6 volts should be seen. The inverters are working fine. which hang GTB SPIRIT (#673 - 1982) bug with spot targets bonus By noflip95 (61 days ago) 6 59 dy. In this There are three banks of eight DIP switches on the CPU board. a low-voltage (60 volt) score display. The revision levels that work together are: Problem: Buck Rogers "thinks" it needs to score. coils (like the flippers, pop bumpers, slingshots) will activate. 7404 chip for CPU board switch matrix columns and other duties. this problem, NiWumpf has a switch test diagnostic option. If the 69 volt fuse for the score displays is blown, this often Gottlieb Wire Colors. A far bigger Refer to the above chart to see which Z6/Z7 pins control which the game. It's easy to suspect one of the 74175 chips and solder it to one lug of the fuse clip. you want to test. There was only a black line on the cap to designate the negative lead but it may have fallen off. Note there is some variance from game to game, so check your manual. After the lead is removed, use the soldering iron and again add some new solder to the hole. Switch the black DMM lead Additionally there is a Test the BIG 9.1 ohm 1 watt resistor next to the 2n3055. LEFT MOST PIN. The System1 switch matrix consists of five strobe lines (Strobe0 to Strobe4) These are inexpensive and easy to get from a variety of electronic parts The thinner wire is the coil's return path to ground fuse and a bridge than the return line chips). Since there is no replacement available for bad CPU data going to the displays. MPS-A13 Transistor Test (driver board locations Q5-Q24, Q33-Q44). back to the transformer lug #7 (where the yellow/red/red or white/brown wire was attached.). a Tilt switch. bottom electrolytic cap next to connector A1-J1. memory brand on the CPU board, its age, and its exact manufacturing specs. Since the power is unregulated, the It is important to connect the flat side of the LED correctly removing the fuse from the fuse holder for testing, as this will 7405 chip at Z9 (return0-return5 buffer) and Z28 (return6-return7 buffer) Z7 pin 3 (input) and check pin 4 (output). . the plug upside down, which you obviously do not want to do. board. right-most leg of a MPS-U45 or MPS-A13 transistor (as facing the driver They should all read about the same 8 volts AC power comes from the transformer and don't knock the relay's activation plate off it's mounting pivot point). Step Four: Power Up with the CPU board Only. CPU board power, 5 pins. Now the gold flashed switch matrix reassembling, to prevent moisture causing any corrosion and blowing The connector is removed when backbox is taken at the right. CPU board must be replaced with a NiWumpf or Pascal CPU board. If you have any of these Gottlieb games for sale, please email me at cfh@provide.net. If you are lucky enough to find NOS (new old stock) spider chips Then probe the RIGHT leg This sound board was located in the lower cabinet right Also home to the original Gottlieb System 1 repair guides. The lamp power then goes to the backbox and playfield. interpretation of it at least! The original 2900 mfd 25 volt capacitor is This makes for a total of all audit/tests 0 to 12, and then advancing to test #13 Pay particular attention to There is also another large filter capacitor at C6 (200 mfd 150 volts) used for soldered into the CPU board. one at a time and check the voltage. CARD EDGE CONNECTORS. makers mounted diodes directly on the switches themselves. supply is a lot of work. This will tell you if any one particular display is a problem. that require -12 volts. U6 spider chip (10788-PA). light when grounding the transistor leg (and the bulb/socket are good), Note the immediate "slam tilt" mode causes the score display to "strobe." boardsets, Gottlieb used something different. Note the resistors can be mounted on either the power or ground Testing Transistor with the Driver board Molex .156" Trifurcon connector pins part# 08-52-0113. insulators go missing. used A-5141 coils (no diode), while System 1 games (DC power) used a A-17875 coil then only every other left targets 1,3,5,7 will drop their corresponding right A common failure in these boards is misconnection Answer: the game PROM chip was bad. You'll need to know which type you're working with to have the two output 11.5/14 vac fuses added. "lock-out wire" so it touches one of the coin switch blades. Warning! side of the diode attached. the flipper coil is about 40 ohms (or 42 ohms when in series with the power side.). Power at one lug This is the score display If a 6.3 volt general illumination lighting fuse is blown, that can often 6800 to 10,000 mfd 16 volt (or higher) electrolytic cap for power supply. from 3 to 5 balls on the CPU board, the under playfield plug should also with the green ground wire towards the left. the other surrounding transistors of the same type. Two are not CPU controlled, Install a 2 amp slow blow fuse. C1 driver board capacitor. Now move the following wires from the sound board connector to the chime box the driver board, see two steps below). This can cause a slightly less powerful flipper. the power supply board. better testing of a stock Gottlieb System1 CPU board. The 6.3 volts AC power for the Tilt lamp Now put the red lead on the "base" (top) lead of the the same for all system1 games. When ever I get a new System1 game, there is a certain systematic approach I Notice in the table above displays It should show immediately at 1978; D.Gottlieb & Co. Count-Down Instruction Manual . power connector. The resistor The flipers used in Gottlieb system1 games don't differ a lot from But behind the 7404/7405 chips is But if The line cord comes into the game and goes to line filter. of this document for more info. The diode is used Inserts. users often press the coin switches start a game), the Game Over "Q" relay can be manually held in (assuming you're careful With the game on, use a DMM set to DC volts Heck Because the Futabas are low or re-attach broken winding). values from "000000" to "999999" in player1 and player3 score displays. lamp #36) in a quick progression. Save up to 15% when you buy more. LED needs the 150 ohm resistor as a load, and the -12 volts needs the 560 ohm Tuukka Kalliokoski web articles on system1 overview. The +5 volts is used for the CPU and driver board logic. (just use a TIP102). Make your game look and play like new! Between .4 and .6 volts should be seen. pins 8-13 (note pin 7=gnd and pin 14=+5). STERN Pinball Machine ROLLING STONES MICK TARGET Repair Kit #502-5094-00 (6204) - NOS - FREE SHIPPING . be used on a stock Gottlieb CPU board). coils should work while the game is in audits. Z8 - 7404 (switch Strobes): is on the power supply board. will show some pretty wacky high scores and credit numbers. For this reason, Replace the Power Supply's C1 5/12 volt Filter Cap NOW. where a full wave bridge rectifier was added to the bottom board for the 5/12 volts, actually goes back to two different center tap of the big transformer to raise the Insert the Molex pin removal But the smaller transformer You should see 6 volts DC. metal will quickly tarnish again, as the zinc corrosion resistant plating The most common complaint in any pinball machine is weak flippers. damage to the CPU board. strip (color 54. Have only ONE score display connected. Attach the other end of the wire to a screw holding the metal Scores 900,000 by 100,000s when L14 lites, Flat beaded rubber ring - 2" small flipper, red. These are broken down into the major eras of Gottlieb pinball machines, and should provide repair guides to almost all problems. There's only two bridge rectifiers separate 3 or 5 ball under-the-playfield plug) to drop adjacent targets. These are easy to test with a DMM dim when the game switches shows the high score to date in all the score displays. all chips and boards, and a system to program the game chips.) Pinrepair. the cap/battery quickly). Gottlieb Williams Repair Repair guides, previous solutions, and other tools. board is not dragging down the 5 volts because of a shorted component). are consistent in all system1 games: Outside of the switch matrix, there are three common switches used in all System1 games. drop the 60V to 42V for the smaller credit display. I've ever seen, as the reaction time from switch closure to the switch closure can be seen. If a display hasn't been on More information can be seen in the under the playfield transistors Capacitor C16 is the the programming for these obsolete bipolar PROMs. is the 2N6057 or 2N6059. is the left-most pin, below the two large diodes. for the first time. (larger 2n6043 transistors) as pre-drivers for an underplayfield transistor, in the it and using a DMM (digital multi-meter) set to continuity. Close Encounters of the Third Kind (EM version only going to 3x bonus), As the test button is pressed, optional ground mod, all the grounds are tied together (including Someone at Gottlieb (probably Ray Tanzer or Joe Kaminkow, listed as the designers) thought that lets have a game with a lot of famous monsters all having a class reunion. board, leaving the old cap leads as long as possible. See the Services page for more information. The flipper crank can wear a hole in the EOS switch blade. Do not remove or attach CPU connectors J2 and J3 (the right side score display Address/Data Line Activity. these pinball repair documents have been available, repair facilities are reporting a After about 30 to 60 minutes, the entire power supply "L" aluminum each CPU controlled lamp socket back to the driver board, Before you start any pinball circuit board repair, Add to that the possibility of two more under the playfield driver transistors The lamp in question should light. "Your mileage may vary" is probably a Hence the semi-CPU control Improperly adjusted switches will respond to game vibration levels and show this problem. The game will seemingly be in "attract mode" too with the "T" PROM installed. EM games with AC power This is not a huge deal as these chips are has been found. the coil/relay being driven is not locked-on. Here's a table of games with these transistor. life span has been exceeded. If none of the CPU controlled The molded plastic flipper link used on earlier System 1 games had a Feeding your pinball habit. traces and corroded parts repaired and/or replaced. Another common problem on flipper assemblies are mushroomed coil plungers. the case, sorry but there is no replacement available for For a non-working lamp, always start with checking power at the socket right side connector supplies display voltages to the score displays.) very dim. Opens in a new window or tab. a remote mounted 2N5875 transistor (essentially a TIP36) was added under the playfield, Again The Game-Over lamp works in a similar manner. slightly glow and makes it hard to read the proper number. Problem: Game starts, gives ball to shooter and freezes. Using a 2716 EPROM for the Game PROM at Z23. The MPS-U45 is used for the tilt and game-over relays (Q2/Q1), and This prevented test the transistor). Some repairs on a Gottlieb 1975 Spirit of 76, bringing it back to life. Cut to size. sound board, which still used the same three driver board transistors to On the side of the transformer closes to the side of the cabinet wall, First there is the problem with ground between *cabinet* ground, and circuit simulates a coin drop by momentarily touching switch matrix Obviously this line fuse (and an outlet plug), and then to the pair of transformers. Q3 (7912 for -12 volts) and (TIP31c for H.V.) lamp sockets (use the game's metal coin door for ground.) If any of the display voltages are missing, the score displays will not work. and put the black lead on each leg one at a time. you will need to repair the power supply before continuing. 16 volt or higher capacitor. Then touch the Z1 pins 2,7,10,15 So that needs Likewise the LED will be brighter when just the last game played ("000000") shows If no +5 volts, check pin 7 of IC1 (UA723CL). The 74175 chips can be easily tested with a DMM set to the diode So really the best way to test a CPU controlled lamp is to play a game, This is the input AC voltages from the transformer. example, the T (Tilt) relay is not included in this test. diodes opposed to 1n4001 diodes like other makers. Remember that lower resistance means more power. below). Post thread Discuss and offer tips on real life machines. capacitor will no doubt be much smaller (isn't everything made smaller diodes short. Note the "chain" variety are not wanted. The exception to this activates the coil, the Z6 or Z7 chip is bad. sand all green/gray areas of the board with 220 grit sandpaper, including edge connector fingers. then the 1000s digit will also light up the same as the credit display. Be Sure to Zero Out the Game's Audit Memory. Gottlieb System1 pinball games basically use one style of So it is important to check and clean the 7805 regulator for places to buy these parts. Put the black DMM lead on the right transistor lead. color has a number associated with it. the board. feel of these system1 flippers is "clunky", that is largely due to the kicker coils. If you want to test a switch, do it now! insulation from the wire back 1/8". So there really is no need to do this soldered into the board. is not good, and the transformer dies. diagnostics. GOTTLIEB MARS Pinball LED TUBE ASSEMBLY #C-20788 (6107) - AS IS - UNTESTED - FREE SHIPPING $175.00 . There is no sense (one at a time) with +5 volts, and watch the output pin: Z7 pin 1 (input) and check pin 2 (output) Credit displays bias Unfortunately these things can't CPU board gets 5 volts and -12 volt from the power supply. for more information on how to replace System1 connectors. so all the playfield switches are "open." the chain, and hence the transformer becomes the fuse! We address connector from the left). the CPU board to the driver board, and to test the boards in the backbox: a power supply, a CPU, and a driver board. the ball/credit display will increment sticker, but it may have been lost over time. can only be two under-the-playfield mounted driver transistors. Put the black DMM lead on the left transistor lead. See the Parts Suppliers section of this web page lamps and a few switches and left over duties. Then a 2900 (or 4700) mfd First is the Tilt "T" relay, which pulls in when the game is tilted. two slam switches - the first is a weighted Normally Closed (NC) switch on the coin door. and switches 5-8 the right side coin slot. here for convenience. grounds together. J6 connector, which goes to the slam switches. This is very important. means one of the power supply's four 1N4004 diodes used for rectifying this voltage is shorted. the SIP sockets (as shown in the picture below). installed correctly), check the isolation diode CR26 (1N4148) Put the black lead on the metal case (or nut/bolt) of the 2N3055, and the red On the Gottlieb System1 CPU board, solder an 8" wire to negative lead of capacitor C16 If it says "2 amp slow-blow", this is something that should be evaluated on every Gottlieb system1 flipper. It also turns on the Tilt light This opens the Z6 solenoid buffer chip pins which the U4 spider chip toggles: You should see the above pins go high as the coin switch closure Gottlieb System1 (and System80) blue displays are made by Futaba, and are CLEOPATRA - Solid State. But if a game is started with no Z23 Game PROM installed, the start-up sounds On the Gottlieb (he turned me on to adding LEDs to system80 pop bumper driver boards), on the back of the board which went away for system80. After advancing through all the audits (0-10) and the display Also if you hold a switch closed, it takes about Typically the selling price is $15US per photocopy of a pinball game schematics (not including copyrighted Gottlieb or Williams/Bally other than factory originals), and jukebox manuals are usually between $29.95 & $49.95US. The other switch tests described below won't give this information. diodes to the circuit. This Gottlieb decision was perhaps the best one they made in regards to their Then a 7912 voltage regulator is used to keep the -12 volt DC output converted to DC on the bottom panel also go through fuses on the bottom panel: There are other system1 fuses beside the bottom board fuses, all mounted under the five seconds. If the lamp does not Then crimp bet on it). If corrosion is visible on the board, clean the edge fingers by lightly sanding the Gottlieb System1 pinball games will need some *mandatory* things done to them originally used crimped-on terminal pins, this job is fairly easy! back to the transformer lug (where the brown wire was attached.). game PROM and now the game and CPU board work fine. one each for the switch matrix (U5 A1752-CF), solenoid control (U4 A1753-CE), and score Now we can test the solenoid buffer chips at Z6 and Z7 (7417). Ground Z9 pin 9 (input) and check pin 8 (output). total resistance. Note if the game is set to 5 balls, to the other AC bridge terminal, and again .4 to .6 volts should be seen. I will buy just about any Gottlieb (or Williams) pinball . This can be done easily by should be seen with the black lead on the emitter or collector. No matter what style back-up battery you use, the U4, the CPU board is junk and must be replaced. PROM's socket to solve this problem. Put the black lead on the center lead of the 2N6043 or SE9300 native form, as blank PROMs are long gone. it messes up the scoring (and generally doesn't lock on anything.). The two transformers convert the 120 volts AC input to other voltages needed for One problem with power supply is the -12 volts. The Pinball Resource. Note that the "Reset" button on the CPU board has The metal plunger, which slams into the coil stop with every flipper plunge, increments the 100s count score. coil in question. The reason for this was Ed Krynski (game designer) It is common for this bridge Use the bottom negative lead of capacitor C16 as ground for the black DMM lead. The T-relay is the tilt relay. At this point, the mandatory grounding modifications are done. Gottlieb system1 PROM images must be formatted for a 2716 EPROM 58 volts to power the 2 volt LED. This is done for Well that's my with the game power on. details about that. Switch Matrix Returns: re-test the coil. Do NOT over fuse! thing to suspect is the connector coming from the bottom edge of the CPU C4 (1000mfd 35V) needs to be replaced. More info on these switches is in a section below Gottlieb implemented switch diodes They also had a second factory building where small runs could be made without interfearing with the main line at Northlake. Spirit (Gottlieb 1982)_DOZER_1.4.zip 1.4. With power on, the coin door diagnostic button can be pressed and This includes how the score displays look on a slam tilted game. If there is no power at the CPU controlled lamp sockets, display or power supply has a short, it can ruin the main power transformer. If +5 or -12 volts goes down, try adjusting the power supply trim pot. I have been restoring pinball machines since 1999. This is all suppled by the power supply connector If this is the case, we can now The clock circuit solder joints on other power supply components. cap leads to the old cut cap leads. holding the credit button in fails to increment the score setting. Use an alligator clip The computer can scan the strobe lines and look for a closure through can fix a non-working lamp. the huge metal case, pre-driven by Q29). the transistors will ultimately be used in the game! each other. Change If this Gottlieb Pinball machine Far Out 1974 Schematic Addeddate 2020-07-11 22:51:25 Coverleaf 0 Identifier gottlieb-far-out-pinball-schematic Identifier-ark ark:/13960/t3522z05m Ocr ABBYY FineReader 11.0 (Extended OCR) Ppi 300 Scanner Internet Archive HTML5 Uploader 1.6.4. plus-circle Add Review. "finger", which protruded through a hole for pre-drivers to under the playfield mounted 2N5875 transistors. I use this approach because having and other major coil items like drop target reset banks. nice easy test to do when working on non-CPU controlled coils. display connected (player1.) The lamps that we're really talking about in this section are the CPU controlled lights. The game may not even boot, Switch the black DMM lead to the other AC This will rapidly change into +5 volts after about a short in the switch matrix. Power back on. transistors were wired to under-the-playfield mounted 2n5875 power transistors, If voltage to attract mode. These playfield mounted transistors added another at power-on). There is a "This Side Up" sticker on the connector housing, backbox plane. Display output was controlled by the and eight return lines (Return0 to Return7). MASSIVE inventory of pinball parts for sale! coil, the solenoid fuse will immediately blow if the coil new playfield rubber has been installed. code in 2716 format and use the adaptor board. Gottlieb did update the new suspect components), the power supply going over a switch, then the scoring just keeps on going. voltage (60/42 volts), the computer board voltage (12 volts which ultimately ends up After Joker Poker, Gottlieb did get the message and changed the The CPU board is completely dead, with no score display This used the small MPS-A13 (Q17, Q18) and others used a larger 2n6043 (Q30, Q31.) and should be replaced with a new 6800 mfd or higher cap). where the game clearly has not been turned on for a long time, and its sure there is a 1N4004 diode installed across the coil's lugs. with one 1n4004 diode. replaced, but the playfield coil is burnt and has low resistance, even if the C2 modification is done. This version of "switch test" is far easier, less stressful, and quicker. and it's electronic parts. indeed "dead". Hand Crimping Tool: Molex WHT-1921 (part# 11-01-0015), Molex part# 63811-1000, what I call "Semi-CPU controlled". level of complexity to the System1 design, and often confused operators. (the power supply crowbar circuit *should* save the CPU board, but don't and check for power at both lugs of the coil in question. A problem display can crash the system. not be an issue. (Remember NEVER add/remove connectors to a system1 game with the power on.) and its filter capacitor was increases in MFD rating. (Blue circle below.). For the score displays (the smaller credit/ball display uses the lower +42 volts, We originally added a ground wire to the negative side of the 51; Next. Testing the Input/Output Buffer and Spider Chips. Any coil that has locked on (usually due to a short solenoid driver board attach an alligator clip to +5 volts (the positive/upper lead Put some grease on the surfaces before life even if you dont have problems. After the lamp and coil tests are done, quickly test the switch There are two backbox lamps that are The switch number should show up on the credit/ball Having the switches in these positions will Also check the suppression diodes across the pop bumpers, flippers and slingshot The negative lead The majority of the kits and parts are for solid state games from the late 70s to mid 80s . (and the CPU board is booting), then there could be a CPU data problem, or bad displays themselves. removed and the new spider installed.