MS2 v3 power led dim usb cable

[robinpipers]

Hello!

When i disconnect my serial cable between computer and ms2 on USB side The red led on megasquirt goes dimmed almost off.
Uppon disconnecting the cable from megasquirt the box resets and led goes strong again.

This aint normal right?

[Blown88GT]

Where is computer getting power from: internal battery, AC power adapter, car battery?

[jsmcortina]

That's probably not a power-LED either.

James

[DaveEFI]

Hello!

When i disconnect my serial cable between computer and ms2 on USB side The red led on megasquirt goes dimmed almost off.
Uppon disconnecting the cable from megasquirt the box resets and led goes strong again.

This aint normal right?

Which red LED?

[robinpipers]

D16, Have to add that u5 gets hot and f1 is burning hot.

[robinpipers]

Using laptop on battery.
Tried measuring D19, 546 ohm one way , 333 other way.. compared to other diodes on board that have infinite in one direction..

[DaveEFI]

Sounds like you have a short on the 5V rail. Have you got a Stim? What you need to do is to power up MS off the car to find out if it that short is inside MS, or in the wiring loom. Ignore the laptop connection till this is sorted.

[robinpipers]

Sounds like you have a short on the 5V rail. Have you got a Stim? What you need to do is to power up MS off the car to find out if it that short is inside MS, or in the wiring loom. Ignore the laptop connection till this is sorted.

Don't have the stim, but i have a DC power supply

[DaveEFI]

Sounds like you have a short on the 5V rail. Have you got a Stim? What you need to do is to power up MS off the car to find out if it that short is inside MS, or in the wiring loom. Ignore the laptop connection till this is sorted.

Don't have the stim, but i have a DC power supply

Ok - remove MS from the car and power it up from that supply. If a high current supply, feed via a 1 amp fuse. Does U5 still get hot?

[rickb794]

The problem may be with the serial cable or how the laptop uses it.

There is a VCC feed to pin 1 & 9 of the DB9.

If your serial cable does not have molded ends you can open the connector and remove the pin 1 & 9 wires.
Or you could cut off the MS end of your serial cable and install a new DB9 male using only the wires you need for an MS (ground #5, transmit #2 & #8, receive #3 & #7).
I believe those pins are straight through the cable, test before cutting off OEM plug.
You don't want to mod the MS because some serial adapters (like a Blue Tooth) need power from that #9 or #1 pin to function.
Cables are cheap leave the computer and the MS alone, label the cable so it doesn't give you trouble trying to use it on something else.

[robinpipers]

The issue only occurs when disconnecting the usb cable from my pc.
Gonna try hook it up to my powersuply

[rickb794]

Are you using a recognized (MS compatible) USB adapter?

Is this an adapter only or an adapter combined with a serial cable.

FYI it is not recommended to use a USB adapter with a long USB cable.
They are notorious noise problems, no USB cable is best.

Like https://www.diyautotune.com/product/usb ... nerstudio/

[robinpipers]

its an rs232 usb serial cable, Tried ms running of powersupply, same issue. If I disconnect cable from pc then current goes up to 1.6A but I suspect the cable.

[DaveEFI]

Power consumption of MS with no load is only a couple of hundred (ish) mA. You need to find out why it is taking more before concerning yourself with the laptop connection.

[robinpipers]

Maybe i failed expaining. When the box is connected to power supply i think current was like 200 ma or something less. And then i connect my cable, it doesnt change at all. But when i pull the end out from the pc not the megasquirt but pc usb connection and leave the d-sub in megasquirt, this is when the power goes up.

[Blown88GT]

its an rs232 usb serial cable, Tried ms running of powersupply, same issue. If I disconnect cable from pc then current goes up to 1.6A but I suspect the cable.

Maybe i failed expaining. When the box is connected to power supply i think current was like 200 ma or something less. And then i connect my cable, it doesnt change at all. But when i pull the end out from the pc not the megasquirt but pc usb connection and leave the d-sub in megasquirt, this is when the power goes up.

Can only be one of these three:
1. the USB cable
2. the RS-232 cable
3. the adapter (there's a chip inside)

#3 needs to meet the compatibility list. FTD chip is preferable.
http://www.msextra.com/forums/viewtopic ... 01&t=27316

[DaveEFI]

Then you need to find how why the current goes up when you unplug that cable.
BTW, I'm not sure what an RS 232 to USB cable is. Normal way is an RS 232 cable with a RS 232 to USB converter at the PC end. The converter being powered by the PC.

[rickb794]

#3 needs to meet the compatibility list. FTD chip is preferable.

Even if this is a device on the recommended list, it sure sounds like it has taken a long walk on a short pier.

Switch USB to RS232 adapters and recheck.

https://www.diyautotune.com/product/usb ... nerstudio/ Ninja fast shipping!