Th-15 power light comes on and goes off but there is no sound

Whether you are experienced in electronics repair?
if not, try this simply way:
1: Test whether the power amplifier is still working. See figure 1.
Power OFF,adjust the EQ settings as shown in the picture.
Minimize LEVEL.Switch ON Power. Touch pin 3 at the INPUT socket by using a small screwdriver or piece of wire / cable.
Slowly raise the LEVEL,a little bit only (as the clock showed 7-8) until
sound is heard in speaker. If not heard, slowly raise again LEVEL.
If audio input signal is heard,it can simply be taken to mean
that the amplifier is working.
If LEVEL at 9 o'clock position,and the audio is not heard,
the possibility of the amplifier is damaged.
Switch OFF the power. Take it to a repair place.


2: When the Power LED is lit, but no sound,
There are many possible causes, one of which is:
I have been getting 3 times similar cases, and all are caused by
two Rectifier-Diode (either or both.) damage on the power-supply-unit.
Remove/desolder,measure, if damaged replace it with a new one.
See figure 2-3.




Hope it helps. Regards.

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"How to replace bass driver in mackie thump 15a".
Did you mean,disassembly the speaker enclosure?
Just remove the 16 screws at the rear cabinet, using a screwdriver.
Then remove the 4 screws that secure the speaker, using the hex key. Is the bass driver blown up / broke?

As Tom Jones sang 'It's not unusual....' The amp has probably gone and you need to get it fixed. These are not the most reliable and I would suggest getting something better from another manufacturer if you can afford it, perhaps a local shop would do you a trade in if they can fix it?

You failed to give us the most important information... what brand and model of the mixer? Youwill use balanced interconnect lines to a balanced MAIN output jack, assuming it exists...

After removing the back cover disconnect the tweeter cable form the terminal. Then hold the tweeter magnet and turn it anti clock wise. The driver unit will unscrew and come of the horn assembly.
Keep the driver unit on a firm table and unscrew the four + screws. It has a sandwich assembly which will part into two if you put a sharp knife and twist. You will see the tweeter diaphragm which can be lifted up again by using a sharp knife. The replacement diaphragm is available from the below given address
http://reconekits.com/tapcothumpth-15ahorndiaphragmpn0013252-1.aspx

Crackling is usally one or two things my guess would be bad grounding of the amp or bad connection with the jacks or plug it self try to make it crackle on purpose by jiggling the jacks see if it has any effect on the crackling try to narrow your possibilitys

The internal amp is in need of repair. Are there any other symptoms or signs?

It sounds like you have NOT connected the power adapter to the box to power it. The guitar sound won't be too loud as you run the hose to your mouth and pick up the sound with a microphone such as a Shure SM57 which then goes to your amplifier. Without the power adapter the internal amplifier will not produce any output.

This probably means there is a failure and the internal protection circuits have activated. It will probably have to go to a shop for repair.

You have likely lost one, probably the +15 volt power supply... This is possibly a shorted component or a short on the circuit board causing this. It takes some skills at troubleshooting to find this. Sometimes using a thermal imaging camera will show hot spot... other times you have to search with a millivoltmeter. The rude solo light is driven by an op amp that uses both polarities of 15 volts and to turn it on it pulls negative... Hence I suspect the +15 is missing.