Megadrum by Japi - Documentation / Pictures -

[dmitri]

The most probable places for the shorts are there where vcc and gnd are close together.

[japi]

Thanks.
Yes, I see thin traces from the 4851's (pins 8 and 16) that carry vcc and gnd are veeeery close. I wonder if a faulty component could make this behaviour too, it is posible? In that case, should I check one by one or you suggest starting for a particular component?
I'll investigate and keep you posted.

[dmitri]

Thanks.
Yes, I see thin traces from the 4851's (pins 8 and 16) that carry vcc and gnd are veeeery close. I wonder if a faulty component could make this behaviour too, it is posible? In that case, should I check one by one or you suggest starting for a particular component?
I'll investigate and keep you posted.

Faulty components can cause it as well. First disconnect Analogue and Digital boards and check for shorts on them separately.

[japi]

I'm making synthex's 2.5 right now, so everything is in one board.
http://www.japiwebcam.com.ar/japi/megad ... /index.php

If I take a hi res image, would you be so kind to take a look at it and tell me if you see something suspicious ?

[dmitri]

I'm making synthex's 2.5 right now, so everything is in one board.
http://www.japiwebcam.com.ar/japi/megad ... /index.php

If I take a hi res image, would you be so kind to take a look at it and tell me if you see something suspicious ?

If you don't see it close up, I don't think anybody will see it on an image.
Did you check for shorts before soldering anything?
Does the meter show exactly 0 Ohm and in both directions?

[japi]

Yes, i checked before soldering, and repaired a short between pins a,b,c of the 4851s. I don't recall the ohm reading I just remember that my multimeter beeps when I measure vcc and gnd anywhere on the board. I'm at work right now, later when arrive home I will measure and post it here.

[japi]

My resistance between vcc and gnd is about 5 ohm, sometimes it will fluctuate a little in readings like 10-20 ohms but it settles at 5 ohms
Thoughts?

[dmitri]

My resistance between vcc and gnd is about 5 ohm, sometimes it will fluctuate a little in readings like 10-20 ohms but it settles at 5 ohms
Thoughts?

In both directions? No ICs installes?

[japi]

Yes, in both directions
No IC are installed, everything else is installed

[dmitri]

Then either you have a short which only you will be able to find or one of the decoupling capacitors (those between vcc and gnd) got broken. Your choice is either:
a) start de-soldering capacitors one at a time and checking resistance between vcc and gnd and if it doesn't help, search the pcb very carefully for shorts.
b) search the pcb very carefully for shorts and if it doesn't help start de-soldering capacitors one at a time and checking resistance between vcc and gnd.