I have been wanting to build a mini amp, but know didly about it. So I bought one of these:
http://cgi.ebay.com/Low-Voltage-Audio-Amplifier-Module-Based-NJM386...
Great price, a no brainer, throw a speake and a Jack in a cigar box vila instant amp.
Well I conected the parts and the little screw mounting box thingie for the power input seemes snafued. If I wiggle it arounfd it works a little but I can not seem to figure out where it is defective, if I touch the wires on the bottom of the board on the solder points it does nothing, figured it should make direct contact. So now what?
I did not want to pry the contacts apart as it is a rather delicate small thing and would likely break.
I would chuck the whole thing and not worry about the $8 investment, but I spent time cutting up a nice box and would make a great looking amp if I could get this thing to work somehow, and incites would be appreciated. Or maybe I am just to pig headed to give up yet.
Cheers Ron.
Replies
Cheers Ron.
I will now get the thing secured inside the box make a grill out of something, maybe just some Bamboo strips so the sound is not blocked and the speaker does not get punched.
So thanks again all of you for your help. Cheers Ron.
I'm not saying you've definitely got it wrong - it's quite possible I've got confused in trying to figure out what I'm seeing in the pics - but you might just want to double check that aspect of things. The risk in connecting power the wrong way is that electrolytic capacitors can be vulnerable to damage from reversed voltage, so go careful.
One other odd thing. What's the dotted line on the circuit diagram all about? It makes no sense to me at all. Did you draw it on or was it there already?
Glad to have you help, no dumb questions here, I am good with them all.
I have a guitar cord, as in a cord with 2 jacks on each end one end is plugged into the amp, the othe end is plugged into a jack on the guitar, the guitar has a bar piezo in it.
So I have done:
I plugged the cord into a regular amp and it all worked well, so things are working up to the jack on the mini amp.
I connected the speaker as it is in the cigar box to a regular stereo, and it worked well.
I changed the battery clip/wire piece.
Tested the battery, it was fine but changed it anyways.
I have some fluorescent lighs in my shop and they will make the piezo buzz if I place it on my workbench. So the thing will buzz when everything is briefly working, telling me the speaker, piezo and powere are all connected.
The things I am less sure about are:
It battery connected with the right polarity, the battery has + - on it and I can see by looking at the underside of the board which is the ground and which goes to the amp parts, which one do you think should have the + on it.
I have one of these multimeters, but do not know how to use it.
The connector block does not feel solidly mounted on the circuit board it will move a little. looking on at the block, like in the photos it will move back and forth a little but not side to side. So if I wiggle it, the battery connection one, it connects and dis connects. If I touch the wires to the bottom of the board nothing happens.
So I am assuming it is in this block.
Huntz:
I will try to connect the wires with the little bars going up and not down, like I have benn doing.
Thank you both for your help, which gives me a few moe things to try.
Cheers Ron.
When you say "If I wiggle it around it works a little" what exactly do you mean? (ie. does it actually give you proper amplified sound from the guitar or do you just get a crackling sound or something like that?)
I figure in these circumstances it's always worth asking the questions that seem too dumb to ask - can't do any harm and sometimes it turns out the solution is so obvious it got overlooked. So here goes...
Is the battery OK?
Are you connecting the leads with the correct polarity? (I ask because I can't see any + or - symbols to indicate which way they should go)
How confident are you about the other connections (input and speaker)? And have you checked that your guitar lead is OK?
Does the connector block feel solidly mounted on the circuit board or is there any slight movement?
I guess it's possible the battery clip could have a dodgy connection in it somewhere - if so it would be simple to swap it for another clip.
These problems are generally much easier to sort if you have some sort of continuity tester. One of my best ever investments has been a cheap digital multimeter which has a continuity testing function built in - you put the probes one either side of the section you want to check and it beeps if there's a good continuous electrical connection. I guess you could use a battery and a small light bulb as a crude alternative.
Cheers Ron.
cheers Ron.