uh oh, i REALLY screwed up this time..advice? help?

[pinkjimiphoton]

ok, so i ordered the pcb for bajaman's mini klone thing, the sagitarian charger. took my time, nice build...got all 1% resistors where possible, the whole 9.

here's the page, but ya gotta be a member to see it i think...so i'll post the link, and a pic or two...

http://www.guitarpcb.com/apps/forums/topics/show/5334626-baja-sagittarian-charger-klon-e-limited-time-only





so anyways, i built the buffered version...made sure there was no cold solder, no bridges, looked with a magnifying glass and my glasses on. one of the nicest jobs i've personally ever done.

and then i f'd up.

i accidentally swapped one of the tl072's and the ICL7660... the top tl, if it makes any difference. and then  i fired it up.

oooops.

i gotta loud hum for a second or so, then nothing...can KINDA hear the guitar in the background. the guitar was muffled in bypass. so i disconnected the batt, and started checking over and over to see where  i screwed up. nothing was obvious, so  i figured i'd convert it to the true bypass version, figuring the buffer was screwing up.

i disconnected the buffer stuff, and that's when i noticed i had swapped the two chips. oops.

i tried using some other dual opamps, i had some TL082'S kicking around...no dice.

also tried two other charge pumps i had....no dice.

this thing suddenly could drain a 9volt bat in literally a couple seconds. matter of fact, one got so hot that i was sure it was gonna catch fire.

to me, it seemed like a short in the power supply? i dunno.

but i figure i'm gonna have to replace some parts due to my snafu. i have no idea how to test a chip, so i figure the easiest way is to replace 'em all.

i KNOW the soldering is ok.

do i have to also replace the electrolytics and diodes? i'm figuring i roasted probably everything but the resistors.

i appreciate any advice, and hang my head in shame. 

any ideas? a serious ball breaking is indeed in order, lol...

thanks guys..

[iccaros]

sounds like a short, contently meter and measure all connections along the board ensuring they only go the parts they need. Trace the entire route of power to ground from each connection. This is where a schematic is important as looking at a layout can be hard sometimes.

you have a place here
where you could have a bridge form as + power and ground are right next to each other. look at that part on your board and measure continuity there (if its shorted anywhere you will see continuity  there )

to test the opamps
place them in a breadboard and create a simple buffer



use your volt meter and check AC voltage in and voltage out (this one is a simple unity gain so they should be close) then add a resister instead of the short between the output pin and - signal in. say 1k you should get a larger AC signal out than in.. If so your opamp is most likely ok... (Oscope is better at this)

it looks like that until you find where you are shorting to ground you should never plug this into power again..  So take out all the IC's and check for shorts.. once you sure you have zero shorts to ground place the MAX chip in, then check for shorts? none then put each opamp in and again check for shorts.

[pinkjimiphoton]

thanks bro, i will try and check it all out on sunday, gigging tomorrow. i really appreciate the advice! do you think i will need to replace the caps and diodes tho?

i don't mind replacing parts if need be...i actually put enough money into this puppy to be determined to get it rockin'!!

[iccaros]

depends on how the test come out.

you may have to take caps off the board to measure depending on what is connected to them.
Diodes should be simple to test on board. But that one (I think its a Diode) in the picture I sent, is it in the right way? if its backwards its a direct short to ground. The one right under my arrow?

[slacker]

Plugging the components in the wrong places shouldn't have damaged anything else in the circuit. To avoid any confusion, until you've got it working I'd assume that the opamps and the ICL7660 are dead and use replacements, they might be fine but you don't want to add any unknowns to the debugging equation.

[pinkjimiphoton]

sombeech!!

you were right on the money, there WAS a solder bridge, right in that place!!

i cleared it, and suddenly no more shorted power supply!!

but...still doesn't work...so will go thru the whole circuit point by point tomorrow, and make sure everything is good.

pretty sure i killed the chips, so ordered some others. if it does work, well...i'll have spares for another project!!


thanks for the help!!!

will report back later...peace!

[pinkjimiphoton]

no dice yet. i've checked for continuity and shorts, this thing is AFU. only thing i can think of is to wait for the parts to come in and try again. it's weirding me out..like, somethings gotta be majorly wrong, the cp is reading about 2.6 v, should be reading way different from that...pretty much the whole thing is reading that voltage, but when i pull the battery, suddenly the battery goes back up to 9v from about 6.5.

wtf....


stumped.

[Earthscum]

Have you tried changing out the chips? Or, try pulling the chips, hooking up the battery, and seeing if you're getting 9V or not at pins 8, or their socket point, anyways. If you get the same reading, I'd start taking measurements on resistors. Esp. at the bias section. Any point where you have full DC path rail to rail, anyways.

JMO, though..

[pinkjimiphoton]

hi guys, i sat down today with it and looked at the board, checked everything, and all read good. voltage was wack.
so i looked at the schematic, and discovered the problem...the 1n4742 as shown on the layout at guitarpcb.com was BACKWARDS.

correct me if i'm wrong, but the banded side of a diode is always the cathode, right?

i reversed that one stupid part...and wango....the pedal works and sounds great. really, really nice overdrive that is ridiculously sensitive to pick harmonics.

one dumb diode...sheesh!!! lol

thanks for all the help and advice tho, believe it or not, i learned from it all...thank you!

peace
jimi

[iccaros]

cool, good job, I thought it was the diode...

[pinkjimiphoton]

figures, doesn't it? lol...

it's no klon i don't think, judging from the youtubes i've seen, but is indeed a really nice overdriver tho.