Built the Fatpants. Hooked it up to my testing rig. Hooked up the ground wire. When I went to connect the 9v wire, there was a visible arc followed a few seconds later by the smell of electronics/fried. I get close to 9v at the bias point when the trim is turned all the way up. This has happened twice (the second time is when I saw the arc. )
What would cause this issue?
(http://img.tapatalk.com/d/14/04/28/ha3e8avy.jpg)
There's a short. You need to check for solder joints connected that shouldn't be.
Thanks Jubal. May be time for me to get some glasses I'm afraid. I really have trouble looking for solder bridges:(
Maybe a decent magnifying glass will do.
Is it just me, or is your trimmer not soldered to the ground pad? And you've left off pad 1 on your IC, assuming you're using an LT1054?
Quote from: PhiloB on April 28, 2014, 12:42:01 PM
Thanks Jubal. May be time for me to get some glasses I'm afraid. I really have trouble looking for solder bridges:(
Maybe a decent magnifying glass will do.
Use your multimeter's continuity setting, not your eyes.
GermanCdn, I'll check that when I get home! The BOM calls for TC1044SCPA (that's from memory probably got some letters and numbers next up)
And Jon, that's brilliant. Not sure why I didn't think of that
GermanCDN, those solder points are present...maybe didn't show up well in the pic. I'll be breaking out the multimeter tonight
If D3 isn't securely in place (it was socketed, could this cause the IC TO FRY?
I've checked the continuity around everything related to the charge pump. Including the voltage going to the J201s. There doesn't seem to be any bridges. I'm working from an etched board. There is nothing connected to PINs 4,5,6 and 7. It looks like to me that the 9v comes in at Pin 1 and 8. Pin 3 is ground. So the 'pumped' voltage is out at Pin 2?
Pin 2 according to the datasheet is CAP+. Pin 4 is CAP-, but nothing is connected to this pin. I thought in circuits there had to be a positive and negative? As you can see, I still have trouble understanding datasheets.
Also, I'm using Fairchild J201. The datasheet shows the voltage going into the 'Gate' pin of the transitor as I have it oriented. Is this correct?
It works!! I had one last TC1044SCPA from a no working Kingslayer. After verifying no solder bridges (thanks for the tip Jon) with the continuity tester on my DMM and verify my component values, I figured my diodes must not be making a good connection in the sockets (one of them felt loose). I hit them with some solder, slapped in the IC and hooked up my testing rig and blammo! 17+ volts with the trimmer turned all the way up:) Kid are asleep but I'll bias it later. Will sleep better knowing this circuit is ready to box.
Thanks for all the help (I'd put in an emoticon if there were one for a humble face).
Phillip