Gravity Wave (Verified)

[amcmann95]

Quick question for everyone-- My voltages all match except for the lm324, which is low-- around .3v. *However*, when I pop it out of the socket, the voltages match perfectly. Problem with the chip Im guessing?

[m-Kresol]

sounds like could be the chip. If you have another one, just try it out.

Could also be that only with the chip inserted you have a connection to something that is then pulling down the voltage. Which pins are out of spec?

Also, what is the problem with your build? No LFO? No Sound?

[amcmann95]

Thanks for the other suggestions m-kresol. Its pins 10, 12, and 2.

I have no LFO. The only pot that really does anything is the dimension pot. Anything with the lm324 isnt working, including the rate led

[m-Kresol]

ok, so this means you are loosing your reference voltage VB2. since VB2 is only connected to the IC, it would suggest a defective IC.
I would replace it first and hope for the best.

[B0ttleneck]

Hello,
I have a problem with my gravity wave:
I made a homemade PCB and assembled everything.
I made a first test yesterday without putting the footswitch but the result is not good: I have an osciliation output mixed with the sound of the guitar (distorted). pots seems to works.
audio (i play with the pots):
#Invalid YouTube Link#
https://youtu.be/iPWAUoPTICU
Photos:https://imgur.com/a/fGBKqGY

 
Where to start checking?
Has someone already had this problem ?

Thanks for your help

[m-Kresol]

Hi bottleneck and welcome to the forum.

Please check the guidelines for getting tech help here: http://www.madbeanpedals.com/forum/index.php?topic=902.0

go through the individual points and you will likely find the problem. So basically, visually check your component values and orientation, check your soldering for solder bridges or cold joints. Check DC voltages on all ICs and transistors (reference voltages by Cody at the beginning of the post). If you can't find the problem yourself, post the voltages and pictures of your pcb and we'll try to help

happy hunting

[HurricaneHordak]

Hello, yous guys! 

I was wondering, is this pedal 'verified' to work at all with the components detailed in the b.o.m. in the .pdf file, or am I supposed to do some of the substitutions mentioned? In the process of double/triple checking everything I was wondering, if those subs were crucial in any way.

Atm, mine doesn't make a sound when engaged. Seems like the signal goes to ground at some stage, because it's so damn quiet at the output. Haven't been able to pinpoint it yet though with the probe or staring at it for an hour.  I get lfo noises around the lm324, and I have something of a chorus-ey signal + a tremolo-ey sinus tone at pin12 of the pt2399. Since my theoretical background is almost non-existent I'm often-times confused about what is supposed to be where sounds-wise and feel like I'm probing in a circle. 

[HurricaneHordak]

Alrighty, after finding my superfluous connection between R33 and R15, naturally, I also had the dim pot issue many people had.
I went the C9 = 3,3 nF route + the 4,7 uF for C20, and now I have quite the spiffing pedal. 

[Hoffy84]

Hey Guys,
Sorry to dig up an old thread.
I built a Gravity Wave, and have it on the test rig. Everything is working good, but I too am having the Dimension pot problem. Starts whining between 10-20%. I had done a lot of reading before this build, so I thought I'd be proactive, and went ahead and did the ( C9 change to 33n / R9 change to 10k ) from the start. These are the only mods I did to the original schematic. Before I start dicking around with things, I was wondering if anyone else had this result with just these changes? I thought about changing C20 to 4.7uF, but wouldn't this just make the rate speed slow down a bit? I don't think it would have any bearing on the whining at the dim pot issue.

Thanks, Jeff

[Hoffy84]

I did some screwing around and got it sounding so much better. Changed the C9 to 3n3, R9 to 1k, and C20 to a 4.7uF ceramic. A few others on the forum did these three mods so I tried it, and it’s a big improvement. No more whining or the DIM pot, but I do get that “motor-boat” effect past 30%. It’s cool though, because there’s noticeable reverb up to 50%, but anything past that is unusable. Changing C20 to 4.7uF makes the rate wayyyy more in range.
This is my first pedal build with a finished enclosure. I’m pretty happy with it. Still have to box it up. It’s not perfect, but OK for a first build. Here’s a couple pics so far. (I have a thing for “The Life Aquatic”. I know it’s a hated movie, but....)