Bipolar charge pump using the max1044 low voltage problem

[SweetFx]

So I’m building a late 60’s fuzz face clone and I found a charge pump schematic on ggg and built it using the max1044 IC. My pedal works but is extremely quiet. I need to crank my amp to hear it. First thing I tested was the voltage getting to my circuit. Instead of -9v it’s only getting -0.3v! I’m not sure what I did wrong and am kinda stumped what to do next. One thing I noticed is that C1 and C2 differ from the layout and the schematic. I used 47uF caps like the layout did. Should I swap them out for the 10uF like in the schematic? Also could be that I messed up the wiring of the charge pump but I can’t find where that is yet. The first component in the charge pump gets the full 9V then only 0.3V at the end. Any insight would be super appreciated! Thanks in advance!

SweetFx

[duck_arse]

hey sweet, here's the thing - we know the ggg drawings are good, because many have built them w/out trouble. and we know your build is bad, because you've just told us. so, if you show us your build, we might spot what you've done wrong, and where.

tl;dr - please post photos of your board.

[SweetFx]

Yeah you are probably right. I just wasn’t sure if anybody else had run into the same problem. I get a lot of schematics off of ggg so I didn’t think it was the schematic. I was just questioning if the difference in the cap values made a difference in function of the charge pump. I’ve posted some pictures of my board. I already had it wired out of the enclosure to test it before boxing it. It’s a PPH board. I have a ground rail (right side of board) and power rail( left side of board). Sorry if the board is hard to follow. Thanks

SweetFx

[duck_arse]

well. I'm not an expert on charge pumps, that's for sure. you'll need one of the regular users to come past and look, but, until they arrive ....

I don't think the 47uF caps will be the problem. first thing tho, make sure the two Ge transistor cases are not touching. then, measure the voltages around the charge pump circuit - the input voltage, the transistor voltages and the IC pin voltages, and post them here for when the crowd arrives.

and yes, hard to follow.

[italianguy63]

You may try disconnecting the charge pump part of the circuit from the effect.  Measure the output again.  Make sure the effect does not have a short, and pulling the voltage down.  If you have a short, the IC is probably hot.

47uf should work... I use 10uf as the pump part (C1).  100uf as an input filter, and 47uf (C2) on the output side (filter).

Also, I have experienced problems with the transistor switching properly.  Try replacing the 1K resistor with a 10K.

MC

[italianguy63]

Here is what I do for reference:




Also, in the future... don't use the MAX1044.  Substitute a LT1054, TC1044S, or ICL7660S instead.  In all these cases the SJ1-BST is closed.  Ignore the SJ2-LV part.

[SweetFx]

Thank you all! I swapped out the 47uF caps for the 10 and the pump came to life! My guess is that I had a solder bridge somewhere that I couldn’t find before and that resoldering might have fixed it. I also did find a short in my fuzz circuit that I fixed so now it all works! Thanks for the suggestions and help! I did hear the the max 1044 was not the best IC after I bought it. Thank you for listing some better equivalents! When the max burns out I will swap it for one of those. It was my first time building a charge pump and it seemed so simple....but somehow still messed it up haha thanks again.

SweetFx