desmond

hie, i have tested those LED which cannot light up cause by other pins shorted are range from 0.6 volt to 1.4 volt .. 0.6volt to 1.6volt is not enough to light up the LED which typical Forward voltage is around 2volt. Do i have any method to indicate those pins are actually not shorted due to the voltage is available but just not enough to light up LED? it has been a headache since many this pins will affect that and that will affect this .. all drops below the forward voltage of a typical LED. Thanks a lot. Desmond

thanks, sure i dont mind to wait for it. one thing that i dont understand is .. how can i test the pins without connecting any power to it? even if testing using multimeter, there is also certain voltage is it? maybe i still cannot get what you mean, so i will wait for your schematic .. really thanks a lot .. :)

harlow, nettron, even if i tested each pair of pins each time .. it still have a little problem, that is if i am testing pin 6 and pin 7 (pin6 connected to 5volt, pin 7 connected to ground), when pin 7 shorted with pin 8 (this pin is not connected to anything), the LED between pin 6 and pin 7 wouldnt light up, because the voltage across is only 0.6volt. if in this case, what can i do?

sorry, here is the datasheet PS11036.pdf

harlow MP and nettron, thanks so much for your reply. I have found the datasheet of the chip and i have attached it here. To be precise, the problem occurs this way. The LED which i used needs 2 volt forward voltage but i have tried 1.8 +/- is enough for it to light up. If i connect the LED parallel with for example pin1 and pin2 .. if pin2 and pin3 (this pin is not connected to anything) shorted (soldering short), the voltage between pin1 and pin2 will drop to 0.6 volt or some others are 1.1 volt which is not enough for the LED to light up. So is there any LED or component which can used as an indicator can be function with that little amount of voltage? or maybe how should i design the circuit for that? Thanks.

yes, that thing is just sit at the top of the chip on the board, i dont really know how the chip internal circuit works, that's why i can only measure the resistance in between each of the chip. when i switch it on, the LEDs supposed to be light on, whenever the pins are short, the related LED in between the pin will OFF. but here comes a problem, as you seen in the chip circuit diagram, the pin 26(P2) and 27(U) are connected into the chip, when i switch on, the LED sits between this two pins couldnt on, just seems like a short circuit scenario. the resistance of P2 and U is very big till 500k when no voltage supplied. i suspect the resistance will reduce to a very low measure when i supply the 5 volt into it. if in this case, how can i check the short circuit in between the P2 and U? thanks again ..

here is the chip circuit which have a little external circuit thanks for advance. 1.zip

hereby i attached my my circuit diagram to you, which is a failed one, because when the pin1 and 2 shorted together, the LED between pin2 and 3 will OFF too .. due to the short circuit. besides, there are some external circuit on that PCB, among the pins, there are some resistance range from 4k to 10M ohms. i am really in urgent this project, hopefully can get your advise thanks. circuit_diagram.zip

yes, i had this idea too, but the problem is i need to test one short for 26 pins together, how am i going to design the circuit? i was stucked in the beggining .. pls advise :( thanks.

I am a beginner in electronics design, currently i am stuck in a simple project, hopefully i can get some advise from you how to solve it. I am current doing a simple project on short circuit checker. I have to check on some pins of a chip on a PCB. I need to touch on the pins at once and check out exactly which pins are shorted, for example there are 10 pins, i need to know whether pin1 and pin2, pin2 and pin3, pin3 and pin4 and so on are shorted or not .. I am only allow to use 5VDC power supply. At first i was planning to use LEDs to design a always "ON" LEDs simple circuit, when the pins are shorted, the LED will go off, but i failed to do so. there are internal connection among the pins, some have 200k.ohms, and some have even M.ohms Hopefully i can get your reply .. Thanks in advance Regards, Desmond