hey guys came across a new problem and i think i know the root of the cause.

but wanted to make sure before messing with them. can anyone tell me in detail as to which pot does what ? i dont have the board in front of me at the moment so i cant tell what number is what. normally when i look at it i have the face of the unit facing towards me when i have it in the car with the LED lights facing me.

so far as info that i can find on the pots is how to reset them. by turning them all the way counter clock wise to reset them, and from my data logs the tach and spark signals are really jumpy . i do have the car idleing nicely , just having like hick ups around 2000-3000 .

i have ms1 ver 3.0 if that helps any .
just need to know which pot does what. thanks in advanced guys.

PS does anyone know of a program i can DL that can read the wave lenths of the CAS or something as in signal strenghts?

 

I found the information in the pages of www.megasquirt.info/ms2/vradjust.htm

and www.megasquirt.info/ms2/v3components.gif

Have a look

 

i found this , and sadly for some odd reason i cant go to those links scca =(


Install and solder R52 {CT94W104-ND} and R56 {CT94W103-ND}. These are the trimmer potentiometers used to 'tune' the VR circuit. The longest lead (and/or the one nearest the "1" imprinted on the case, depending on where you got your components) on each pot should go in the square pad closest to the heat sink. R52 is used to adjust the hysteresis, R56 is used to adjust the zero-crossing point. For VR sensor operation, the pot on the transistor base (R56) needs to be turned to zero volts and the pot on the op-amp feedback (R52) needs to be turned to maximize resistance (i.e. give 100K feedback resistance). This should be with both screws turned fully counter-clockwise. For more on adjusting the VR pots, see this link.

and i found this link
http://www.megamanual.com/index.html

 

"couldnt get the pictures to load.."

Adjusting the V3 Main Board VR Input Circuit Potentiometers
The V3 main board variable reluctor (VR) sensor input circuit has two pots for adjusting the trigger voltage and the hysteresis.

R56 is the potentiometer nearest the edge of the PCB, near the copyright date. This is the voltage trigger adjusting pot.

R52 is the potentiometer near the center of the PCB. This is the hysteresis pot, and determines how low the voltage must drop before the circuit output drops to ground. Turning this circuit clockwise can reduce the effects of noise in the input signal.
For example, if the VR sensor transitions from negative to positive at the trigger point, going through zero volts (called the "zero crossing") the slope should be steep there. The VR circuit inverts it so the negative-to-positive VR transition becomes a positive-to-ground digital output (VROUT) to the processor IRQ line, and this is what triggers an IRQ (a tach signal).

To adjust the screws for the pots for VR sensor operation, the pot on the transistor base (R56) should be adjusted as near zero as possible (fully counter clockwise), as this is where the VR signal is most stable (all other settings depend on the slope of the signal's rate of change, and hence on the speed of the VR sensor and it's maximum voltage). The pot on the op-amp feedback (R52) needs to be turned to maximize resistance (i.e. give 100K feedback hysteresis). This should be with both screws turned fully counter-clockwise. The pots don't actually stop when fully counter clockwise, instead they have a clutch that lets them spin at the end of their travel. You might be able to hear and feel a slight click when this happens.



Try this on the car and if there is noise on the tach VR signal then adjust the hysteresis pot (R52) clockwise until the noise vanishes. If you turn it too far there may be too much hysteresis and cranking signal may be difficult to trigger on.

The VR input circuit should be capable of triggering in the millivolt region, if it requires one or more volts to trigger reliably then you should suspect a component or inadequate soldering.

You can improve the common-mode rejection of the circuit (common mode rejection is the ability of the circuit to 'ignore' the effects of noise that occurs on both signal wires at the same time). Here is the first thing to try: take the VR return wire, the one you have been connecting to ground, and put in a series resistance, like 47K or so, and connect the other end of the resistor directly to the wiper of the zero-crossing potentiometer (R56), marked "2 2" in the schematic below, which also goes to the base of Q23 (the "2 2" indicates pin 2 on the pot and pin 2 on Q23). Next move the zero-crossing point potentiometer setting off of zero volts to a point of, say 1 volt or even higher (measure the voltage at the wiper). Since the return point of the VR is also at this junction, the VR sensor will also be biased up the same amount, so the circuit will still sense zero crossing properly. In fact, it does not matter where the zero-crossing pot is set in this case, since the return VR sensor lead will also be biased by the same amount. But what this does is allow rejection of common noise introduced in the VR wires by the op-amp.

 

discovered that i needed to move my grounds of my megasquirt as they where picking up a whole lot of noise from the engine. and i redid that cas wires with shielding so now the signal is very clean now thanks to that.