Small speaker not working

[Nexo]

Hello everyone!
I've been trying to figure out what's going on with a speaker I have, is a small one and is not working. What I tried was this:

1. Make sure that the cables that connect to the mains are working correctly. They are.
2. Make sure that the trasformer is stepping down the voltage from ~110V to ~12V. It is.
3. Make sure that the cables which connect the transformer to the bridge rectifier are working correctly. They are.
4. Test the bridge rectifier. Here is where I have a problem because when the speaker is turn off I test continuity in every diode but the meter doesn't beep. Am I testing it right?
5. Another thing is that this circuit is small and has a potentiometer with an on/off switch just like the one showed in this page: https://www.adafruit.com/product/3393

And it's a bit weird because when the knob is in the off position, there is continuity between the brige rectifier's cap's terminal but when is in the on position, there is not. Plus, when I turn on the speaker (being connected to the mains) and measure the voltage between the bridge rectifier's AC input it shows only 2.4V AC but when I place the know in the off position, it shows 11.4V AC. Maybe is a short circuit or something?

Then, I touch the diodes and sometimes one gets really hot but other times it doesn't. It's quiet confusing to be honest.

I'll upload a few photos in a bit.

Thanks in advance for your comments!

Edit: To add 2 photos

[barry14]

Could you provide some information on what this board does, a schematic, and what kind of speaker.  How do you know the problem is the speaker?

[Electro Detective]

The yellow amber product sab0tage glue on the components would be my Number #1 suspect,

heated up and picked off VERY carefully and patiently bit by bit     before continued troubleshooting.

Tip: Cut and pick off the darkest amber blob first on the left side and test the speaker, before continuing on.

It looks like a giant link bridge, perhaps across components likely to get warm and mis-behave

You might find the device comes back to life immediately

or at best expose a corroded part or PCB trace, and or a partial intermittent bridge/short due to the reaction with the glue

Either way, ALL the yellow glue has to go, otherwise it will always bite you in the future as it heats, cools and eats away at the components and or shorts them 


Clean up with non residue alcohol and use a clear hot glue/gun to secure components that need it once you're back in business,

and good luck   

[Nexo]

Could you provide some information on what this board does, a schematic, and what kind of speaker.  How do you know the problem is the speaker?

Of course!
Here is an image explaining a bit this circuit.

[Nexo]

The yellow amber product sab0tage glue on the components would be my Number #1 suspect,

heated up and picked off VERY carefully and patiently bit by bit     before continued troubleshooting.

Tip: Cut and pick off the darkest amber blob first on the left side and test the speaker, before continuing on.

It looks like a giant link bridge, perhaps across components likely to get warm and mis-behave

You might find the device comes back to life immediately

or at best expose a corroded part or PCB trace, and or a partial intermittent bridge/short due to the reaction with the glue

Either way, ALL the yellow glue has to go, otherwise it will always bite you in the future as it heats, cools and eats away at the components and or shorts them 


Clean up with non residue alcohol and use a clear hot glue/gun to secure components that need it once you're back in business,

and good luck   

I did what you told me, did my best but it's still not working. I tested the diodes with a multimeter and it gives me readings no matter the polarity, all 4 of them. Are they damaged?

[Electro Detective]

All the glue gone?

cable prod and tidy with a wooden toothpick?

Use a magnifier just in case a cable whisker is touching something

Otherwise you have a component fault somewhere, or everyone's favorite...cold solder joint/s