Hey guys,
This is my first amp build and i have to admit i thought it would be easier. I'm using a kit from qkits and i thought it was as simple as wiring up a speaker, a 9 volt source, and a mono jack for the guitar cable. I'm probably just missing something, but the circuit isn't working and i'm not sure where the problem is. I bought 2 boards and wired them both the same way, so i can eliminate the board as a problem. The speaker works and the battery is good. I didn't solder any wires in the second one i built, so i don't think the solder joints are a problem. I've included some pictures. Am i missing a ground wire somewhere?
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Everything looks to be wired correctly as far as I can tell from the photos so I'm going to ask the obvious question.
Did you turn the amplifier volume trimmer up?
I used a similar kit once that shipped with the amp volume control set to zero.
David,
I ordered the board pre-assembled, so if it's wired wrong, they did it at the shop. But I ordered 2 boards and they're both assembled the same way. I guess they're either both wrong or both have bad components. Which seems like it would be a rare occurence, but within the realm of possibility I guess.
David Lloyd said:
I think both Naz and David may be on to something. From looking at David's hand-drawn schematic, the location of various naughty bits, and your pic, I can see the half moon dimple indicating pins 1 and 8 on your chip. So why are the speaker leads on your board closest to pin 8? In David's diagram they are closest to pin 5. And Naz makes a good point: a pic of the other side of the PCB might help...just a thought.
Here's a pic of the same board from the Q Kit website; you can see that the dimple is toward the caps and transistors, while on yours it appears to be 180 degrees away from them:
http://store.qkits.com/images/qk17.jpg
Nope, dangit; it was just a shadow. Rats...
Close-up, in-focus pics of BOTH sides of the PCB and all the off-board wiring would enable people to give you a better idea where you went wrong.
Hi Nate,
I have made a few smokey type amp circuits using the LM386 and had one I couldn't get to work until I realised I'd put the chip in the socket the wrong way around (the half moon on the top of the chip goes at the pin 1 and 8 end on the schematic if you have one.)
On the simplified circuit of a smokey amp like this
Is there any possibility this could have been done on yours?
Regards
David
Hmmm. Ohhhh-kayyyyy...
So A is out, #2 and #4 you did...you have a 3-lug RTS input jack, wired up properly...OK, really stupid "Tech Support" question: You plugged in a guitar, turned up its volume knob, with the amp turned on, and you get nothing, in either case?
Yeah, doesn't seem likely you would get 2 bad assemblies...your wire gauges look different from those pre-wired to the board, so there's likely an impedance mismatch, but you seem to be getting enough power to at least light up the LED, so the mismatch if any is small...
Did the kit come with a schematic, and if so could you post a pic? You might need to take this over to the CBG Amp group, run it by them; pretty sure a number of people there have used this same kit. I confess to being stumped.
Thanks for the replies. I did check it with a guitar and an iPod plugged in, but didn't get any noise with either one. I also wired in a potentiometer on the speaker side just to see if it would do anything, but still nothing. I'll admit I'm not an electronics technician and this thing is just boggling my mind. I'll head over to the specialists. Thanks again.
Oily "Strat-O'-Nine-Tales" Fool said:
Oily "Strat-O'-Nine-Tales" Fool said:
Was gonna ask if you could go through these steps ( maybe you've done some or all of these already...):
A) Check your wiring schematic one last time.
1) Test the circuit at all points with a Multimeter, or wire and alligator clips. I have a fair amount of trouble getting small precise solder beads, so it could be a short where you soldered to the board?
I assume the IC chip was already attached, but it is possible to burn it up accidentally by applying too much heat for too long... 2) Check the input jack to make sure the tip and sleeve lugs have been wired for the correct polarity.
3) Because you demonstrably have power, the problem is most likely at the speaker end or the input end ( although as suggested previously, a bad chip or other component might be also be the culprit)
4) Desolder everything, strip to bare wire, and try hooking up with everything just twisted / taped together.
If none of these work, send it back for a replacement.
You also need to be sure you don't burn out any components when you are soldering. Using a heat sink will help.
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