xprog k line

[ste 228]

Hi all ive bought a china xprog m 5.84 and on testing seems ok using usb port for power .... in this next test i had nothing other than a scope connected to k line..... however when you test for imobilizer bmw ews 3 which uses K LINE for coms and monitor k line you get a neg square wave and then a positive spike then after a short time a comms error ...fair enough what you might expect but if you connect a 12v or 15v ext power supply and do the test you will find the 2 x 33 ohm resistors R159 and R160 under the pcb which is efectivly just 16 ohms in total these kline resistors are in q2 collector start to burn up dosent happen when powered by usb..... another strange thing is when external input power 15v in the pins labelled +12 goes to 15v as well without external power all seems to work this seems it may have a design flaw as if anyone uses this on external supply it will fry the 2x 33 ohms under the pcd i have the 5v rail the 3v rail and 12v available and the unit programs 8 pin ee proms and seems to function ok.... the vcc rises from 2.2 to 5v on program its just the k line that has a problem with external power supplies .From the diagram if q11 is turned on then the 12v or 15v will connect via R158 2.2 ohms straight to kline and the 2 x 33 ohms and if q2 is on it will then go to ground this is what i think happens and with a larger current input power unit it burns up the resistors maybe the resistors need to be changed to a higher value i will have to check the circuitry further.. this is a brand new unit i wonder if anyone else has had these resistors fry and burn under the pcb might explain why some cant get the bmw EWS-3 to work. i would be interested to know what others have found with their units as ive just started and not impressed with it so far

[ste 228]

UPDATE..........UPDATE...... tested unit again and it seems if you use usb power during k line read in bmw imobilizer EWS-3 mode it works the +12v actually gets taken down to 5v so the resistors dont fry up ...however if you use usb and ext power either 12v or 15v then when in k line mode the resistors burn through pcb because the 12 or 15v dosent get lowered also note as i said before when 15v ext power used the 12v pins are at 15v when measured... so with my unit you cant use ext power when using k line it may be that if you use serial port and ext PS this may not happen but using usb power and ext PS defininately fries the 2 x 33ohms under the pcb....... hope this helps others

[ste 228]

Another update and looking at the circuit and its response when using K LINE feature using an external power pack either 12v or 15v overides the switching of the K LINE pwm circuit which without ext power drops to 5v... because the resistors are such low value they can cope with the 5v but with 12v or 15v you can watch them burn up in front of your eyes and the pcb with them so be warned if you have this model take care using ext power