#1
http://www.beavisaudio.com/projects/NoisyCricket/

Here is the link to the project.

Basically, I have this thing all wired up and plugged in and when I turn it on the LED gives off light and the speaker makes a little popping sound (I have it wired to a speaker instead of an output jack).

If anyone who is familiar with the noisy cricket wiring or basic wiring troubleshooting could you please tell me why I cannot hear anything out of the speaker except the little snap when I flick the on switch?

I have rewired the grounding situation and double checked some connections. I don't have a multimeter so I cannot test the individual components, but that would probably be the next step right?

If I put my ear right next to the speaker (Jensen Mod 5/30 8 ohm) I can hear a little change in hum between pickup selections, but it is so quiet.

Any help would be appreciated.
#2
Just looked at the circuit and one potential issue may be the FET in Q1. Did you observe ESD handling conditions for it? If not, it might be blown or damaged. Other than that, checking wiring and component placement might help. Also, verify no solder bridges between traces. Lastly, without an oscilloscope or means to inject a signal and trace it, you're kind of stuck using the shotgun method of troubleshooting. Which version did you build?
#3
I tried to make sure I didn't overheat any components when I was soldering. I used the LM386 chip.

I also used the Radio shack general purpose PCB and it was a pain trying to get all those wires in the tiny holes and soldering them. There are some solderings on the pcb that look really close to bridging, but its hard to tell.

I'll probably get a multimeter eventually if I can't figure this out with the basic troubleshooting methods.

Could it be that the speaker is not powered sufficiently? So there is not sound coming from it?

Another clue!
I have a very scratchy volume pot on my guitar... so I tried messing around with the volume and for a certain portion of the sweep of the pot I can hear the scratching in the speaker, but after the lower 25% of the sweep I cannot hear anything from the speaker anymore...

does that make sense?
Last edited by dougl126 at Aug 24, 2010,
#4
Hmmmm. Does the guitar play okay through another amp? If so, then I'd have to say the guitar is fine, but just has a dirty volume pot. Too bad you couldn't eliminate the guitar completely, by connecting an iPod, or other audio source into the input. If you do that, make sure you keep the volume on the iPod low - and you'll only be able to use one channel. Doing that would confirm that you've built the amp correct and it works.
#5
Thats a good idea, yeah I built the guitar and didn't know the pot was bad until after so I just left it for now. It works though.

I will try some different input devices.

I tried hooking up a smaller speaker to it too and its the same thing. Nothing...
Last edited by dougl126 at Aug 24, 2010,
#6
Some progress, I plugged my computer into the input and the speaker is playing music (not well).

The music plays, but is not very loud and is distorted. But so far so good I guess...
#7
Yeah, it's not the speaker being underpowered. Static on the control pot does tell me you're getting some input, though. If the guitar is ok, the guitar cable is ok, then we really have to suspect something is miswired or there's a short. Did you build the version with the FET in Q1? If so, I still think it could be suspect. FETs are very sensitive to static discharge (ESD). The best way to solder them into a circuit, is to wrap some wire around the leads, so they're all shorted and at the same potential - just don't solder it. Solder the FET into place and then remove the wire. The FET should've come in an ESD bag and may've even been inserted into some black ESD foam. Proper handling of the FET prior to soldering is crucial. If you didn't build the FET version, then ignore all of that.

I'm still leaning hard towards a miswire or short. Did you use the preprinted circuit board, or did you use point-to-point wiring on a perforated board?
#8
Ok. That's a start. How's your battery? If it's a little weak, that could cause the distorted sound. Also, what's the ohm value of your speaker? What value was the amp designed for? It could still be a miswire, short or bad FET.

Also, if you're using an amplified output and the volume is too high, that would cause it. Make sure it's the Line Out and that the volume is kept low - the Line Out from your PC is going to be a higher level signal than the output from your guitar.
#9
Oh yeah, sorry I didn't answer that part. I did use the MPF102 FET.

So I could just get a new one and swap them out and see if that makes a difference.
#10
You could try replacing it, but only if you didn't use the precautions I mentioned earlier. If you handled it without any ESD protection, it could've been damaged. It really all depends on how dry the air is around you at the time you handled and installed it. The higher the relative humidity, the less of a static charge your body will contain. Higher static charges will puncture the thin film of the FET. Probably more than you wanted to know about ESD and damaging electronics, but it's something I've been doing for years.

Unless you got the 386 amp really hot, I doubt it's been damaged. It is not static sensitive.
#11
Hmm, well so far I know it works since I can listen to music through it. Just need to get sound to come from my guitar.

Thanks so far
#13
Haha, this explains the distortion! I forgot I have a gain pot, so I turned down the gain and now its crystal clear!
#14
Well... Given the fact that it wasn't working with the guitar, probably would've never thought to check that one. Any luck with the guitar, or is it still static?

Glad to hear you finally got it going. I know what it feels like to build something, only to have it not work right.
#15
Well this morning I even tried another guitar and cable and still nothing from the speaker but hum.

I can't think of anything. I guess you have to ask why? Well the purpose of the amp is to amplify what comes from the guitar. So if it does that with a computer signal, but not the guitar then what is wrong? Right?

I think I'll go buy a multimeter...
#16
Bumping

Did you get it fixed?

I just built my own and don't want to start another thread since I have a similar problem. I DO get sound from it, its just very low. You can clearly hear the guitar if you put your ear upto it. And it doesn't sound half bad, just not loud. If you touch the speaker you can feel it vibrate when you play.

Ive tried a 12v power source, tried fresh AA's, tried a 9v wallwart.

The Speaker is a 5 or 6"ish paper cone driver 8ohms. It works fine in other sources. Tried another speaker as well.

I probably did mishandle the fet, so off to ratshack to get another(first attempt on protoboard failed and burned up a battery....) Kept wiring the tip/grnd wrong. I had to desolder and pull it off the board.


Something I noticed on the circuit, They list VR2 as being the Gain, but in pcb layout they seem to have switched VR2 and VR3. This changes values drastically. Maybe that's the cause. Also I think I read the wiring wrong and might have connected a wire from the gain pot to the input jack. Also Ratshack didn't have a 1k pot. So I bought a 5k pot for the gain. We'll see what happens.

Something to think about, will post updates
Gear's : Peavey Vypyr 60 Tube | MicroCube | Noisy Cricket | Ibanez S470DXQM Blue Burst | Takamine EG440C
Pedals : MXR M-108 EQ | Digitech Bad Monkey, Sanpera I, GFS Tuner

Seref : Cali would put a health warning on celery if they could
Last edited by Castiel at Dec 17, 2010,