Now I think I know the answer to my own question but worth asking a second opinion.
Ok so failing
1 - it being a positive ground effect (which is NOT the case)
and
2 - a short circuit or solder bridge (which there MAY be)
is there any other reason (Im thinking things like a failed cap, or something random like that) which would cause a ground plane on a PCB to register something more than 0v when run with a battery.
Im seeing similar readings to my battery voltage on a home etched Zombie Chorus board.
The effect passes signal, just. When I unclip the ground, the signal passes wierdly.
With battery, and grounds wired up, I have to really crank my amp to hear anything and what I do hear is a very fuzzed out signal, but something.
Im hoping I havent fried my Mn3007 :(
Anyone confirm its just likely a solder bridge that'd help my peace of mind, but im damned if I can see one.
Is your battery heating up? I ask because that usually the first sign that your power is leaking to ground. Try putting a quarter on the two poles of a battery and you'll see what I mean.
If it isn't heating, than it might just be a weird glitch. My first suspect would be a bridge though.
Jacob
Yeah I think it was.
Damnit.
This is a 1590A layout for a zombie chorus, its tiny.
Gonna get out a magnifying glass.
Kinda annoyed my DMM doesnt have a continuity buzzer on it, that would be super handy right now.
Quote from: jkokura on December 06, 2011, 02:32:04 PM
Is your battery heating up? I ask because that usually the first sign that your power is leaking to ground. Try putting a quarter on the two poles of a battery and you'll see what I mean.
If it isn't heating, than it might just be a weird glitch. My first suspect would be a bridge though.
Jacob
Just tried this again and no I dont think it is.
This is infuriating. Ive scraped with a blade around all the suspected traces and that hasnt helped.
At this point a continuity tester is the first tool I'd reach for too. If you're not registering 0 at GND and ~9 at the +9V pad, you will have issues.
Jacob
ok
so I figured something out.
In the process of chopping the board to fit the box, I cut some corners (literally).
the top part of the ground plane wasnt connected to the rest of it. Now I have "jumpered" the ground planes together, I get 0v at all the ground planes.
Problem now is that I still get the same issue.
Do you reckon I have fried a chip?
The chip in question is a CD4046 of which I dont have a second one to test on hand.
I guess I can ask the designer what his voltages are on the pins.
Thanks for your help.
PS does it make sense that if part of the ground plane became seperated as described that you wouldnt get 0v at ground?
I can't say if your chip is fried. It is possible you still have a problem elsewhere. If you've got +9V and 0V where they should be, Audio probe is your tool now.
I have read that the Zombie Chorus is a fickle beast anyway. Is it a verified layout?
Jacob
Supposedly verified, yes. Will crack the audio probe out later.
Voltages seem reasonable on the CD4046 and MN3007.
I can alsways test the MN3007 in some known good circuits of mine.
thanks for being a soundboard ;)
If both pins 2 & 6 of the 3007 have the same voltage on them (most likely around 3-5V) that should show the clock is working.
ill check, thanks.