Sida 1 av 6 Troubleshooting Your V3 MegaSquirt 2008-05
Contents
1. e Jumper TSEL to VROUT Or VROUTINV if you install both sets of near the 40 pin socket want the VR input to be inverted on the bottom side of pee z he e Jumper OPTOIN to TACHSELECT on the bottom the PCB near the center other side of the PCB near the DB37 connector opposite the heat sink e Jumper TSEL to OPTOOUT on the bottom side of the PCB near the center b If the Hall sensor input is noisy run the ground from the Hall sensor to one of the jumper slots on the DB 37 connector like DB37 pin 6 for SPR4 then connect SPR4 to XG1 Remove the jumper from XG1 to XG2 Twist the signal wire DB37 pin 24 and ground wire DB37 pin 6 together all the way to the ignition module this will further reduce noise in the signal Note that you will have to ground XG1 with a jumper wire to run on the stim c If you have an intermittent signal but it doesn t work at all speeds or all temperatures in the car check the Hall circuit modifications here Hall input circuit mods 2 If you have no rpm it may be because the stimulator may not have the voltage to overpower the D2 diode which must be jumpered to test MegaSquirt on the stimulator This diode D2 is needed if e Your ignition system has a large offset bias most systems do not have such a bias e You are triggering directly off the coil negative terminal So to start you can either solder in a jumper wire in this location or you can install the diode D2 and then install2. come on at all then you need to check you soldering of the DB37 very very carefully to make sure there are no bridges and no solder flux left in the pins Use the schematics and PCB layout to help you h If that checks out connect the lead of the tester to the very small via hole near the backside of the stim connector lead in the boot header hole nearest H1 furthest from the CPU in line with the Pump label adjacent the resistor R1 The LED should flash If it doesn t you need to check that the 555 timer on the stim is operating If it does flash check the soldering of the pins on the stim s DB37 connector i The stim is not actually powered directly by the battery Instead the 12 volt supply powers the MegaSquirt EFI Controller which then powers the stim via the 5Vref lead So check that you have 5 00 0 07 volts at the MegaSquirt regulator assuming your multimeter is accurate This is installed on the under side of the MegaSquirt PCB The outer pins are 12 Volts actually 9V from the stim and 5 Volts to the stim The middle one is ground So check the out two ones against the center or the boot header hole nearest H1 furthest from the CPU with the LED or preferably with a meter You should get 9 volts and 5 00 0 07 volts j If you don t get 5 00 0 07 volts on the regulator U5 pin furthest from the DB9 connector next to it the stim and most of MegaSquirt isn t getting any power Check the soldering of the regu
3. for the flyback The flyback damp 12V is on the bottom of the PCB This trace could be cut and ran thru a spare connector output Best bet would be to run this wire direct to the injector 12V source in order to complete the damping circuit and to separate this from the MS 12V source 17 Finally if none of this helps to discover and solve your problem send a message including any information you found from doing any of the above to the MegaSquirt Forums Feel free to ask for help that is why the MegaSquirt forums are there just realize that you may be sent back for more information You will solve your problem much faster if you provide as much detail as possible when asking questions the first time around And following the assembly steps you will discover problems and correct them as you go along If all else fails you can have someone else troubleshoot and repair your MegaSquirt Peter Florance who runs an electronics repair business and who is a very active and informed member of the MegaSquirt community has offered to troubleshoot and repair MegaSquirts for those in need The fee is based on standard shop rates with a hour minimum You can contact Peter at peter firstfives org Various MegaSquirt schematics and other info for troubleshooting MegaSquirt V3 Main Board Information and Schematics MegaSquirt V3 External Wiring Diagram MegaSquirt V3 Main Board BOM V3 Troubleshooting MegaSquirt II Daughter
4. on the LED tester and be sure they flash Note that the driver inverts the signal so the flashing may look a bit different but it should still flash at the same frequency d The signals arrive at Pin 1 of the FETs Q1 amp Q5 on the heat sink and are fed out to the stim LEDs through pin 2 Both of these should flash with the LED tester If the output pins are flashing then you have a problem with either the DB37 or the stimulator itself Recheck the LED orientation and the soldering of the DB37 connectors and the stim LEDs D2 D3 and stim resistors R5 R6 12 If you have trouble with the Throttle Position Sensor reading in MegaTune the problem is most likely with the wiring at the TPS Refer to the TPS section of the wiring guide for more information However if it also gives problems on the stim you need to look at the following components to make sure they are correct C8 0 001 C9 0 22 and R9 1K Ohm Check all the solder joints as well Also make sure there is no excess flux around the affected components If all of these are okay you need to look a bit deeper Disconnect the stimulator and remove the 68HC908 processor The TPS signal connects to pin 26 of the CPU so you might check that this pins is soldered properly You can measure the resistance of R9 directly on the board it should be about 1K Ohm 50 ohms R9 is above the amp in the copyright notice You can also check the resistance from the CPU pin 26 ne
5. the injector will generate a current from the collapsing magnetic field that flows thru the FR302 diode the TIP125 transistor thru the 12V feed and back to the injector The 12V feed to the MS is used as a path Note that this is the closed loop path this is not ground referenced the 12V is used as a return path not as the potential source Now if the 12V line has resistance then this current path will cause a voltage drop across the line Ohm s law If you have ever used one of those portable lights on the long extension cord with the built in socket trouble light and ever ran a tool from this outlet you may notice that the light bulb dims down whenever the tool is active This is due to the resistance in the extension cord wiring and by drawing more current the wire drops some of the available voltage and this is seen in the light More current means more voltage drop for a given resistance Now if the extension cord is a large gauge wire then the voltage drop is less http www megamanual com ms2 V 3trouble htm 2008 05 10 Troubleshooting Your V3 MegaSquirt Sida 6 av 6 Same thing applies here in the 12V line Depending on the path of the current thru the 12V wiring from the raw 12V MS feed back to the injector 12V feed there are many places where could be potential voltage drops Things like small gauge wire resistance in contacts like relays and MS connector etc can all add up You can also use the separate 12V lead just
6. 1 amp Q5 if you used a metal screw to secure them have not have there insulation cut through by the screw Also if you haven t yet wash the board in 99 isopropyl alcohol as recommended in the assembly guide Other possibilities are for low voltage are shorts most likely caused by solder bridges Check very carefully to make sure there s no solder bridges on the installed components including the 40 pin CPU socket and the DB37 connector If those are OK then the next thing to do is pull up one leg of each component diodes and caps at a time by melting the solder of one leg with a soldering iron and pulling the leg out of the PCB with needle nose pliers until you do get 5 Volts on the regulator pin and CPU socket See the schematic here to find the applicable components url http www megamanual com ms2 pcb htm url 1 Hall sensor input issues a If you have no rpm signal to MegaSquirt and you are using the Hall Optical Points input circuit verify that you have a XG1 to XG2 jumper in place on the MegaSquirt main board MegaSquirt will not receive ignition pulses if this jumper is not there See assembly step 52 for more details Check the other ignition circuit jumpers as well For the VR sensor For the Hall sensor optical sensor coil negative terminal or points e Jumper VRIN to TACHSELECT on the bottom side of the PCB near the DB37 opposite the heat sink _ OR Do NOT e Jumper XG1 to XG2 on the bottom side of the PCB
7. Card MegaSquirt V2 2 Main Board Schematics MegaSquirt V2 2 External Wiring Diagram MegaSquirt V2 2 Main Board BOM V2 2 Troubleshooting MegaSquirt Stimulator Assembly Instructions and Schematic e MegaStim BOM e Relay Board Assembly Instructions e Relay Board Schematic e Relay Board BOM e MegaView Assembly Instructions and Troubleshooting e MegaView Schematic e MegaView BOM Last Updated 02 23 2008 22 05 40 MegaSquirt is an experimental device intended for educational purposes MegaSquirt controllers are not for sale or use on pollution controlled vehicles Check the laws that apply in your locality to determine if using a MegaSquirt controller is legal for your application 2004 2007 Bruce Bowling and Al Grippo All rights reserved MegaSquirt is a registered trademark http www megamanual com ms2 V 3trouble htm 2008 05 10
8. Troubleshooting Your V3 MegaSquirt Sida 1 av 6 Show v3 0 Component Map Troubleshooting Your MegaSquirt V3 Main Board If you have put your MegaSquirt together but it does not work this section will help you sort out the problems Often there is something simple wrong and a few simple checks can identify what needs correcting Follow the instructions below Before checking anything else make sure your stimulator has a fresh battery many problems are traced to a low battery voltage but only after a long frustrating troubleshooting effort Also make sure the CPU is in the correct way On an MS I the notch should be closest the edge of the PCB On an MS II the 6 pin header should be nearest the edge of the PCB Before starting have a look at the schematics and PCB layout PDF files you may want to print some sections to help you troubleshoot Read ALL of the troubleshooting tips first then go through the steps Note With 2 88 code the first thing you must do is set the ECU Type under Fuel Set Up General to match your hardware MS II 1 or MicroSquirt 2 MegaTune will not let you change anything else until you do this The rpm will cycle from 0 to 8000 rpm and most of the menus will be inaccessible Do not change settings expect the stim to work load an MSQ etc until you have set the ECU Type MS II 1 MicroSquirt 2 the MS II Sequencer will be 3 This setting applies to MS II derivatives with code 2 88 or higher c
9. a jumper around the two leads of the diode in effect shorting it out The latter will allow you to snip the jumper later on if needed putting the diode back in circuit Note that D2 should not be installed for a Hall or optical sensor it should only be installed if triggering off the coil negative terminal 3 If your oxygen sensor feedback doesn t seem to work recall that the O2 voltage top bar on the MegaTune Runtime dialog is the raw data coming in and it should respond to stimulator input On the other hand the EGO correction bar or equivalent gauge on the tuning screen WILL NOT move away from http www megamanual com ms2 V 3trouble htm 2008 05 10 Troubleshooting Your V3 MegaSquirt Sida 2 av 6 100 unless you have the EGO correction parameters set properly and MegaSquirt senses the proper inputs to activate EGO correction Don t confuse EGO and O2 voltage EGO is a kind of integrator function that acts on the O2 voltage So O2 should respond EGO will only respond if MegaSquirt has been on for more than 30 sec the current rpm adjusted on the stimulator above the EGO active above rpm threshold EGO step and limit do not equal 0 and the coolant temperature above the coolant temp activation These are set on the enrichments window of MegaTune 4 If nothing else seems wrong but your MegaSquirt doesn t work as expected check your soldering Check all the solder joints visually for solder bridging and exces
10. ar the H1 boot header to R9 on the side of R9 nearest the DB37 you should have less than 1 0 ohm 0 1 is better on the side of R9 nearest the DB9 you should have 1K Ohm 13 If you are having trouble getting values to stick in your MegaSquirt EFI Controller check your power supply Typically a bad power supply will allow you to set values but they will revert to the previous values after powering down PC power supplies are especially notorious for this and should be avoided 14 a If your MegaSquirt starts up fine then fades and dies the issue may be C22 On the stim MegaSquirt might die after a few seconds in the car the engine might start and run for several minutes or seconds or not at all Using a wall wart adapter instead of a 9 Volt battery might help on the stim but possibly not completely By far the most likely cause of C22 giving problems is it being in backwards C22 is a polarized cap meaning it has to go is a certain way the positive lead wom should be furthest from the heat sink It is a small cap with an even smaller symbol imprinted on it and it is easy to get it in the wrong way C22 is used on the Vref output circuit If C22 is failing it might not conduct when cold but when warmed up it could short the 5 Volt supply to ground and MegaSquirt will not run Note that on the stim a dying 9 Volt battery can give similar symptoms so check that first Also if you do not find the problem in the ste
11. cohol rubbing alcohol and a soft toothbrush Remove the entire PCB from the case first and remove the CPU Clean it gently being sure to get the alcohol around each of the components on both sides Then allow it to dry completely before reassembling and testing it again Also look carefully for any solder joints that may not be perfect Cold solder joints are joints that look okay but have not bonded properly to the solder pad on the PCB Cold solder joints often look grey or powdery after a while These will often work okay at room temperatures but not when hotter or colder If you have any doubt reflow the solder joints with a hot soldering iron hold the hot soldering iron against the joint until the solder melts again and flows out over the solder pad 10 The LEDs flash briefly when MegaSquirt is powered up with the bootloader jumper in place However they also flash and go out if no rpm signal is received The Warm Up and Accel LEDs do not light coninuously even if the conditions for them are appropriate until an rpm signal is received So this will make it look like no code has been loaded If you suspect problems with the stimulator for example everything seems to work but there is no RPM indication in MegaTune follow these steps a Do you have RPMC installed Some people have had trouble finding a supplier for one and assumed the stim would work without it It doesn t b Check that you have installed D1 and put a jumper acr
12. lator as well as the soldering flux etc of pins 26 and 28 If you do have 5 00 0 07 volts then check that it makes it to the 555 on the stim k Pin 8 on the 555 chip on the stim is its power supply Without 5 volts on pin 8 the 555 will not operate even if it is in working condition Pin 8 is closest the CLT pot Check the voltage on pin 8 light the LED or 5 volts using the boot header hole nearest H1 furthest from the CPU for a ground If you don t have 5 volts after checking all the previous items check for inadequate soldering and excess flux around pins 26 and 28 of the stim s DB37 1 If there is 5 volts at the 555 then it is likely that the 555 or the T1 transistor 2N2222 or ZTX450 is fried if you don t have 5 volts see the previous step You can get these at low cost at virtually any electronics shop like Radio Shack etc 5 for 3 Cut the legs off the old one while it s still on the board and de solder the pins a braided copper wick or a vacuum sucker also available at Radio Shack etc Then put a new 555 in and you ought to be functional You might want to solder in an 8 pin socket then insert the 555 into that it makes later repairs easier 11 If everything seems to work in MegaTune including the RPM but the injector LEDs don t light the most likely problems people have is either the LEDs are in backwards or the PWM is set to near zero Note If you have a MS II controller with version 2 88 c
13. noisy 12v battery signal spikes to 17v dips to 7v was to decouple the flyback 12v lines both TIP125 s from the MS 12v input pin and run them back to before a noise filter on the 12v input of the MegaSquirt To do this lift the 12v pin of each of the TIP125 s in the flyback circuit The TIP125 are Q9 and Q12 the ones with the mica insulators The 12V pin on the TIP 125 is the pin in the middle melt the solder and pull the pin up with needle nose pliers Then run a wire from each of the pins you pulled up independently back to the raw 12v supply outside of the box and before the noise filter You can ran the wires through the spares SPR3 and SPR4 which go to DB37 5 and 6 20ga is just fine Here is a little explanation on the flyback during PWM A 12V l il Injectors INJ wire l Injector Energized 12V ilj Injectors FR302 INJ wire PWM Off Flyback Damping The top drawing A shows the current when the injector driver is on during the high time of the PWM waveform Basically the FET is turned on energizing the injector This is the PWM high time and it depends on the setting of the PWM duty cycle The second drawing B is the path when the driver is turned off during PWM flyback damping or recirculation mode This occurs during the off time of the PWM current limit During this time the injector is trying to maintain the current that was there during the PWM on time see Lenz law So
14. ode and on the stim the INJ1 LED is always on but the INJ2 LED is flashing normally and you are running V2 88 firmware make sure you have ECU type set to MegaSquirt II 1 instead of MicroSquirt 2 Then cycle the power to MegaSquirt i e turn the power off then on This should fix that particular issue If these are okay then you need to check that the FET driver U4 is receiving signals from the CPU Then you need to check that the FET driver is sending the proper signals to the FETs Then you need to check that the FETs ground the pins properly so that the LEDs are getting the correct signal To do this build an LED tester as shown above step 6 Set the stimulator s RPM pots to indicate about 1500 RPM on MegaTune Put the ground end of the tester in the boot header hole nearest H1 furthest from the CPU a The CPU sends out signal to the FET driver on pins 21 INJ1 and pin 22 INJ2 near the L2 inductor Recall that the pins are numbered starting with 1 at the corner with the dot an are numbered counterclockwise from there Check these on the LED tester by putting the positive end of the tester against the pin and be sure they flash b The FET driver receives the CPU signals on Pin 2 INJ1 and Pin 4 INJ2 on the side of U4 closest to the CPU Check these on the LED tester and be sure they flash c The FET drivers sends out signals on Pin 5 INJ2 and 7 INJ1 on the side of U4 closest to the DB37 connector Check these
15. ode only 0 Is your stim battery powered The battery might be dead as they only last a few minutes while powering MegaSquirt So replace the battery with a fresh one If that doesn t help remove the processor and check the voltage at the voltage regulator US You should get e stim voltage 9 Volts on the pin nearest the DB9 e the middle one should have less than 1 Ohm to ground use the heat sink or the center pin of the voltage regulator as a ground and e 5 0 Volts on the pin furthest from the DB9 If you don t get 5 0 Volts there s a short somewhere The most common cause is the pins of the voltage regulator itself having a solder bridge but it could be a bridge on almost anything you ve installed so far a diode backwards or a polarized capacitor backwards C22 is a likely candidate Also check that C15 and C16 are the right way around if they aren t discard them and get new ones they will be toasted It s also possible that one of the diodes is backwards I would check them all but especially D9 D10 D11 D12 D13 and D19 But check ALL the diodes again even if you have checked them already you sometimes have to look several times before seeing something like this this is most likely the cause If you installed components on the heat sink that required mica insulators Q12 and Q9 make sure you are getting around 60K Ohms resistance to ground between the heat sink and the tab of the component Make sure the FETs Q
16. oss D2 or jumpered both of these positions if directed to do so in the instructions If either D1 or D2 are open the rpm signal will NOT reach the processor c Check that you have installed the correct jumpers for either the VR or Hall input circuits step 52 of the V3 assembly manual For the VR sensor For the Hall sensor optical sensor or points e Jumper VRIN to TACHSELECT on the bottom side OR Do NOT e Jumper XG1 to XG2 on the bottom side of the PCB of the PCB near the DB37 opposite the heat sink install both sets of near the 40 pin socket e Jumper TSEL to VROUT Or VROUTINV if you jumpers chose e Jumper OPTOIN to TACHSELECT on the bottom want the VR input to be inverted on the bottom side of one set or the side of the PCB near the DB37 connector opposite the the PCB near the center other heat sink e Jumper TSEL to OPTOOUT on the bottom side of the PCB near the center d If you have installed the jumpers for the VR input circuit instead of the Hall circuit you may have to make some very careful adjustments to the VR circuits pots R52 and R56 to get an rpm signal to MegaSquirt With a VR sensor on the VR input circuit Start with the R56 pot all the way counter clockwise and R52 about 6 to 8 turns clockwise from the fully counter clockwise position The fully counter clockwise position is reached when the pot clicks you can feel and might be able to hear this The pots are 25 turns from the fully clock
17. p above check your soldering as described in step 4 14 b One the other hand if the MegaSquirt won t respond at first when cold or won t start with a serial cable and laptop attached but works normally after a few seconds of powering up or a few cranking tries then suspect D19 On a V3 board D19 protects the 5 Vref from voltage spikes The supply is 5 Volts so the Zener diode rating must be higher than that otherwise the diode will conduct all the time and fail quickly from excessive heat current In theory 5 1 Volts is okay However in practice these diodes typically have a tolerance of 10 meaning that a 5 1V Zener diode may conduct at 4 6V and thus http www megamanual com ms2 V 3trouble htm 2008 05 10 Troubleshooting Your V3 MegaSquirt Sida 5 av 6 conduct all the time heat up and fail A 5 6V can be as low a 5 1 Volts which is fine Also these diodes have a temperature dependence their rating when cold is lower than when hot actually Zener diodes greater than 5 00 volts act this way diodes rated less than 5 00 volts have a higher rating when cold So you should replace D19 and moving up to a 6 2 Volt Zener diode such as DigiKey 1N4735ADICT ND would be a good idea it provides slightly less protection but potentially much better reliability 15 If you serial connection doesn t work or has stopped working and you have tried the tips here connection troubleshooting guide you need to do some hardware trouble
18. p should be closest to the www megamanual com in the copyright label U2 The notch in the pin 1 should be in the square pad furthest from the heat sink U3 The notch in the pin 1 should be in the square pad closest to the heat sink U4 The notch should be towards the heat sink If you have a dot instead of a notch the dot should be closest to Q9 on the heat sink U6 The notch dot should be closest to the DB9 connector U7 The notch should face the heat sink connector If you find some that are incorrectly installed de solder them and turn them the right way around it is likely that they are not damaged EXCEPT for the tantalum capacitors C16 amp C17 that should be replaced if installed incorrectly 6 You can use an LED in series with a 330 ohm or 270 ohm resistor and probe the input and output of various circuits like the injector driver to make sure that these are working Solder the resistor to either leg of the diode then solder a lead 20 22 gauge wire to other end of the resistor and another to the other end of the diode Use heat shrink tubing or electrical tape to ensure that the leads cannot contact each other Strip a bit off each end of the wires to use as probes or solder on a bit of the leads you have cut off other components while assembling MegaSquirt EFI Controller etc http www megamanual com ms2 V 3trouble htm 2008 05 10 Troubleshooting Your V3 MegaSquirt Sida 3 av 6 LED sib insula
19. s flux e Solder bridging is when the solder from one lead has a tail that touches another lead shorting the two components together it indicates that too much solder was used If you have a solder bridge use a piece of fine braided copper wire and a hot soldering iron to soak up some of the excess solder e Excess flux generally shows as a shiny transparent scale on the surface of the PCB You can wash it off with acetone or 99 isopropyl alcohol and a toothbrush then rinse the PCB in hot water and let it dry completely generally overnight is sufficient e Also look carefully for any solder joints that may not be perfect Cold solder joints are joints that look okay but have not bonded properly to the solder pad on the PCB Cold solder joints often look grey or powdery after a while These will often work okay at room temperatures but not when hotter or colder If you have any doubt reflow the solder joints with a hot soldering iron hold the hot soldering iron against the joint until the solder melts again and flows out over the solder pad 5 Next if the soldering is perfect but MegaSquirt still doesn t work as expected review the assembly guide Check each step to make sure that you have not missed any components Verify that all components that have a particular orientation polarized are installed correctly this includes all ICs all polarized capacitors all diodes and LEDs the MAP sensor the voltage regulator and the transis
20. shooting On a V3 main board the following should be connected DB9 pin 2 to MAX232 pin 14 DB9 pin 3 to MAX232 pin 13 MAX232 pin 11 to CPU socket pin 12 TxD MAX232 pin 12 to CPU socket pin 13 RxD Each of those should have less than 1 Ohms resistance between the two test points If they don t resolder the appropriate connections You should check that you have 5 0 Volts 0 10 on the MAX232 pin 16 and ground on pin 15 Use the middle pin of the voltage regulator as a ground for measuring the voltage and check that you have less than 1 Ohms resistance between pin 15 and the center lead of the voltage regulator If you have your MAX232 in a socket make sure the MAX232 is well seated in the socket The associated components for the MAX 232 are on a V3 main board C26 C27 C28 C29 Make sure they are the right components and are well soldered and not bridged If all of the above are okay replace the MAX232 cut the legs then remove the body of the IC and unsolder the legs one at a time to avoid damaging the PCB The MAX232 does not tend not to wear out so the amount of use isn t important but they can fail after a few hours if they have seen a static shock at any point 16 If you have MAP sensor spikes that aren t traceable to back fires etc and you are using PWM to limit the current to low impedance injectors you might have to modify flyback circuit The fix for this specific problem noise in the sensor signals and a
21. te 390 Ohm resistor Test point Test the probe by connecting it across your power supply It should light connected one way but not light when connected the other way around Now you can use the ends of the wires to probe the circuits for signals the led will light or flash if it gets a signal positive voltage The longer lead of the diode goes to the circuit you want to probe for a positive signal the other lead from the side of the LED case with the flat on it goes to a good ground such as the heat sink 7 Check to see what if any functions work Try the loopback test the serial communications test the clock count up of the processor and check for power and ground to the pins of the MC68HC908GP32 processor see the assembly guide steps for details Verify that no components are touching the crystal Y1 which might prevent it from working properly 8 Note which if any of the LEDs light on the Stimulator and under what conditions If your are able to isolate the problem to a particular area of the MegaSquirt EFI Controller check the schematics for that function and double check all the related components for correct value orientation and proper soldering 9 The most common cause of a MegaSquirt failing after it has been working for a while is excessive flux residue The flux residue can absorb water from the air and short MegaSquirt internally The solution is to clean the PCB with e 99 isopropyl al
22. tors e Verify that each component is the correct item for each location Pay particular attention to make sure the correct diodes are in the correct locations Their markings are very small and they are easily mistaken e Be sure you have not swapped some of the 0 1 uF capacitors at C1 C3 C13 C18 C19 C23 and C26 to C29 marked 104 with the 0 01 uF capacitors at C11 C21 and C32 marked 103 They are very similar looking and the markings are very small In particular check Capacitors C14 The positive lead it will be marked with a small on the right side of the label is closest to R19 C16 The positive lead it will be marked with a small on the right side of the label is closest the heat sink C17 The positive lead is nearest the heat sink C22 The positive lead is furthest from the heat sink Diodes e D2 D3 D5 D7 D8 D11 and D17 have their banded end closer to the DB37 connector e D1 D6 D9 D10 D12 D13 D18 D19 D20 D21 D22 D23 have their banded end closer to the DB9 connector e D4 has its banded end closer to the heat sink LEDs e D14 D15 D16 There is a small flat spot on the plastic base of the LED In all cases this flat is nearest the DB9 connector Transistors e Q2 Q4 Q6 Q7 Q8 Q19 Q20 The flat side should face away from towards the DB9 end of the PCB e Q10 Q13 Q14 Q15 Q22 Q23 The flat side should face towards the heat sink ICs U1 The notch in the chi
23. wise position to fully counter clockwise position With a Hall sensor or other square wave input like an EDIS or HEI or on the stim on the VR input circuit Start with the R56 pot about 6 to 8 turns clockwise from the fully counter clockwise position and R52 about 6 to 8 turns clockwise from the fully counter clockwise position o R52 in the middle of the board is the hysteresis pot o R56 near the edge of the board is the threshold pot Also see www megamanual com ms2 vradjust htm http www megamanual com ms2 V 3trouble htm 2008 05 10 Troubleshooting Your V3 MegaSquirt Sida 4 av 6 e Are you are absolutely sure you have the battery wired in correctly Use your LED tester see step 6 to make one to verify f Check the orientation of the transistor T1 the flat side should face the TPS pot See step 62 in the MegaSquirt assembly guide for some notes on transistor orientation If it is in correctly plug the battery into the stimulator and connect the stimulator to MegaSquirt g Using the LED tester you should be able to get a signal on the LED tester step 6 from jumper from TachSelect which goes to either VRIN or OPTOIN depending on which input circuit you are using Note that the LED tester will appear to stay light continuously if the rpm is above about 400 rpm Try to turn the rpm pots down so that the rpm is 100 or so then you should see distinct flashing If the LED tester doesn t flash it stays on or doesn t
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