somthing wrong

[marcjwebbmusic]

hi all, hope you are good,

today i have had a small problem, i plugged my megadrum digital board in and nothing, it has been working no problem for ages.

whats really bizarre is that with checking what i can with my meter, there is 5v into the usb socket.

the led on board also shows 5v but does not come on at all, the screen registers different voltages and also shows nothing and does not come on.

i get a mixture of voltages on both the atmega and the pic, but still no signs of life

from what i can remember the only thing that shows no voltage is the 1n414 diode, (this i will double check for sure)

i am really confused as to what could be the problem here and some help here would really really be great.

regards

marc

[marcjwebbmusic]

i have definately no voltage on the diode previously mentioned, not 100% sure if there should be.

also, i have connected my analogue board of which a mixture of voltages (mostly around1.5v) up to 5v and some at 0v.

i put the legs of an LED on the pins of the led on the board and the LED lights, constant but on and showing 5V


please can someone shed some light.

[dmitri]

I can only suspect that:
1. you applied 5V in reverse (if even the backlight on the LCD does come on)
2. you have loose contacts or bad (loose) soldering points.

[marcjwebbmusic]

ok, after checking these poits, i have god joints all over, (have redone them) and no backlight r anything, when i plug the usb cable in, i jut dont get any life at all. however 5v is measured through most of both boards and LCD.

i have now changed the 1n4148 just to be sure and it is still doing the same, whats the chances have blown one of the IC's?

regards

marc

[dmitri]

No idea why you think 1n4148 is in any way special to all other parts. Provided you had it before, If you don't have backlight on the LCD either means power doesn't get to so you still have connections/soldering problems or you've blown it with too high voltage - I don't think the backlight LED can blow just from a reverse voltage

[marcjwebbmusic]

ok kl.

with regards to the LED i mentioned in the first post, this is relating to the midi/signal led. this just has a constant 5v but nothing on the led itself, if this is blown would it stop it turning on properly?

also i have noticed a little brown circle on the 6n138 IC if this was blown, would this also interfere?

i am going to chang the led, (although looks fine) just to be sure.

Regards

Marc

[marcjwebbmusic]

after some more testing i realised using the out casing of the usb socket as a ground, with that i do get 5v in various places however when i use one of the pins of the usb socket (not 100% sure which one is ground) i dont get much more than 0.5v on the signal led.

so this definately looks like power.

ill prob end up making a new board lol.

regards

marc

[ignotus]

after some more testing i realised using the out casing of the usb socket as a ground, with that i do get 5v in various places however when i use one of the pins of the usb socket (not 100% sure which one is ground)

I don't think it's a good idea to randomly pick pins. If that's your approach I'm not surprised it's not working...

Can't seem to attach an image - it's as easy as googling "usb pinout".

[marcjwebbmusic]

its not so much as a stab in the dark, i did mean to state that i was working logically, following tracks through. one of the caps shows no readings when a prob is either side, and seeing as these are non polarised, i have tried both. so as it looks like this could be power related, if one of the caps have gone, would changing this shed any more light?

thanks for your help so far.

regards

marc

[dmitri]

Unless the blown cap made a short between ground and +5V, it would not make the whole board dead.