On a Mackie Thump Th15a loudspeaker, diodes D106 and D107, which diode has reverse polarity?

Contact Mackie direct. They will know which component is failing. Link to the company for one of their powered speakers.

Thump215 15" 1400W Powered Loudspeaker

Mackie https://mackie.com > loudspeakers > thump-series-2022

The Mackie Thump215 15" 1400W Powered Loudspeaker brings the bass for DJs, venues, bands, and more and features a feedback eliminator and music ducking.

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Question edited for clarity

https://elektrotanya.com/mackie_thump_th-15a_sch.pdf/download.html

Or contact Mackie direct
https://mackie.com/sites/default/files/PRODUCT%20RESOURCES/MANUALS/Owners_Manuals/Thump12A_Thump15A_OM.pdf

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buy a canister cold spray and spray on some active components if the noise begins You have a thermical failure in a component on the board can be faltering resistorcircuits or resoldering some active components.

i) I assume the fuse you mentioned was in the mains plug - did you also check the fuse in the TH15A mains input socket? This is accessed by pulling out the tab in the bottom section of the socket (below the centre pin). This is a 3.15Amp antisurge fuse, 20mm type.

ii) If this fuse has blown, then replace it & all may be well ...... but if it blows again, then move to step iii).

iii) With mains disconnected, remove rear panel (outer screws) & check the power supply PCB for damaged components, especially R111 & R112 (100ohms). If the latter are burnt or open circuited, then the amplifier module may have blown.

regards, Dave

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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There is almost certainly a reason the PSU has blown, these are not very reliable units and the amp has probably gone and taken the PSU with it. You are better off taking it to a dealer and getting it fixed. If there is no power on the seecondary and there is no short the transformer must have blown (assuming you're not trying to check with a DC meter)

Almost certainly the amp has failed, as per usual with these, you need to take it to the repair shop and see if it's worth fixing it then sell it once working or for spares if not. Sadly whilst Mackie make some really good kit their powered speakers are not amongst the most reliable

replace diodes D106 and D107

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

The schematics don't show this, however reverse engineering this there are two windings... one is for the phantom power of 48 VDC... this winding needs to provide about 55 to 60 volts DC to the 48 volt regulator. EXPECT around 40 to 50 volts AC on this winding to the full wave bridge of D1,2,3,8.

The +/- 16 volt power regulated by LM317 and LM337 regulators will likely require about 20 volts DC into the regulators. It will be less than 25 volts because there is a 25 volt cap filtering.

Given a 20 volt DC from the diodes D5,6 and diodes D4,7 the transformer will be around 15 VAC either side of the centertap.

A minimum would be 12.5 VAC and say 18 VAC either side of center.

You should see near pure DC across C1 and C2 with only a little ripple of 2 volts MAX. The ripple should be 120 Hz. An oscilloscope is your friend in this area !!!