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Rookie question on speaker hook up in an amp

Please forgive me if this is not the proper place to ask this as it is amp related, not CBG related.

Our kids gave me a nice box which wasn't conducive for a good CBG so I decided to make an amp out of it. Never used a soldering iron before but it seemed to go together OK [a kit from the good folks @ Gitty].

Initially it worked, but the volume seemed low. Then the speaker stopped functioning, although the LED still lights up. I changed the battery to no avail. All soldering connections seem sound and [for a rookie] relatively clean.

Anyone have some troubleshooting tips for me??

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Replies to This Discussion

Permalink Reply by Blind Lemon Cello on April 6, 2016 at 3:06am

Those small amps aren't very loud to begin with. If you have an ohm meter you can test the speaker to see if it is good. Put test leads onto speaker connections & If speaker is marked with it's rating the meter should read the same. If no reading speaker has issue. Another test would be, if you have an earphone jack, to see if that is working, If not it could be the module & or poor connections on both, but not likely. Also check volume pot connections. Hope this helps.

Permalink Reply by Scott aka Farmer Ted on April 6, 2016 at 3:19am

Blind Lemon makes some good points.

Be sure that the speaker rating (in ohms) matches what the amp module is rated for. For example, some modules/circuits are rated for only 4 or 8 ohm speakers. Others may be able to use either 4 or 8 ohm speakers. This is important, because if the speaker impedance does not match the module specs, the circuit will fail.

As Blind Lemon suggested, a tester (ohm meter, multi-tester) is a valuable tool to have for checking these things. One that has a "continuity" function is good. Be sure to check all solder points, especially your ground connections on the module, jack, speaker, battery, etc.

Permalink Reply by gary sheldon on April 6, 2016 at 5:29am

Another possibility is called a "cold solder joint". This occurs when you don't get enough heat on the joint while soldering. The solder gets hot enough to melt, but not hot enough to make a good conductive joint. With the low voltages in those speaker wires, a bit of resistance might be enough to stop the speaker from working.

I say this because you stated that you haven't soldered before.

To make a good joint, first you need to have a good mechanical connection. Then the parts you are soldering need to be clean. The tip of the soldering iron also needs to be clean and shiny. This can be accomplished by simply wiping the soldering iron tip with a rag. The idea of soldering is to use the metal being joined as the heat source. You do this by tinning the tip of your iron with solder, press it onto the joint, then when the joint is nice and hot you touch the solder to the joint. The solder acts to transfer the heat from the iron to the joint. It is a little hard to explain. The joint has to be nice and hot when the solder is applied. A cold solder joint can be either very dull in color, or excessively shiny and bulbous in shape.

Also make sure you have the proper solder. It should have an acid (flux) core. Or you can brush flux on the joint. The flux helps clean things up and it helps transfer heat. Solder used for plumbing is lead free and doesn't work well for electrical connections.

Hope this helps.

Permalink Reply by Kenneth A McAuley on April 8, 2016 at 11:47am

And you can even over heat the joints and that will lose continuity, be care full how you strip the cable, seen more than once big speaker cable hanging on to a speaker on a few strands.
All good advice but it's worth practicing stripping some cable tie a pig, tin your iron and practice on the cable
Ken

Permalink Reply by Kenneth A McAuley on April 8, 2016 at 12:15pm

My first amp in the new ways of a CBG man, 1 30w 8ohm, plus 2 10w 4 ohm,
Sounds great so don't give up
Ken

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