Powered speaker (PA) - powers up, but no sound

[Osborne]

Hey guys!

I'd love your input on what's going on here...

Got a powered speaker setup. It powers up just fine, but there's virtually no sound coming out. If you really max out the source, the clip light lights up and you hear a faint sound coming from the unit. But it obviously doesn't work correctly. BTW, I'm testing with RCA here, but the XLR inputs do the same thing.

Here's a vid:

Any tips on what to check?

 

[panic mode]

based on your description i tend to believe that the output stage is toast.

i normally do visual inspection and then go from output to input and check stage by stage.
1. speaker
2. power
3. output transistors
4. drive circuit
5. preamp, filters, effects

next when asking for help, i would offer anything that may be significant so those in position to help have all info they need:
1. make and model
2. possible link to user or service manual
3. pictures including close-ups of the boards and components (to me, video had little value)
4. your location (you may be living next to one of guys answering these posts)

 

[Osborne]

Thanks Panic. "Outboard stage" ... If it is this, would a fix be something like replacing the capacitors on the board, or more complex?

I'm really green on this stuff, but I want to learn instead of always paying to have repairs done. And this is a cheap little unit - nothing to lose! I'd love any recommendations you have on getting familiar with the basics.

And thanks also for the tips on getting help. Didn't really know where to start.
1. I've never heard of this brand before - SHS Audio.
2. There's no manual online, and there's not a model / serial number on the unit itself. (FWIW, there's a chance it's still under warranty. Looking into that now... but if I could get it fixed cheaply/locally that may be preferable to an RMA.)
3. I'll try to post some later tonight.
4. Nashville.

 

[Nigel Goodwin]

based on your description i tend to believe that the output stage is toast.

I would suggest the most likely problem is the speaker O/C, rather than the output stage (as you mentioned in 1), but it really depends on the exact circuit, which looks unlikely to be available.

Clipping lights are usually fed from the output of the power amp, so that would suggest the amp is fine.

As it appears to be under warranty, his best option is to return it under that warranty.

 

[4pyros]

Do you have any test equpment??

 

[Osborne]

Pictures are here.

I think I found something that's a big deal: look at the last picture. That was at the bottom of the cabinet - loose! Think it's the culprit? It seems... important. Can this be re-attached?
Most photos are of the amp side of things. If it would helpful to see more pics, please let me know what exactly what you need to see in detail.

Like I said, it's possible that the unit is under warranty - but that's still TBD. I thought I'd take the opportunity to learn.

As for test equipment, I have this multimeter.

Thanks again for everyone chiming in. You guys rock.

 

[Nigel Goodwin]

That's a choke from the crossover, which effectively makes the speaker O/C - it comes from the little brown board in the picture above it, it's clearly marked on the PCB.

 

[rmn_tech]

The Item in the last picture is an inductor. It looks like it has fallen off the crossover board. (The small pcb on the smaller speaker (tweeter)). Try removing this board and taking a picture of the reverse side of this board. The designation on the board is L1 1.04mH. Just my opinion others here with more knowledge (experience) may have better ideas.

Best of luck with your efforts.

EDIT. Nigel you beat me to it

 

[Osborne]

More photos (the last 6 are the most recent).
You'll see where the inductor is separated, then I seat it, then I flip the board.

There are two little nubs on the conductor that set into place on the board. Then there are two copper wires coming from it - one stubby, one long. The shorter wire looks like it should just solder to the board right where it is (that's what the smaller inductor does).
But I'm not sure where the longer wire needs to go.

View attachment 68671


Also, Nigel (or anyone) - what is O/C ("speaker O/C")? I've looked all over the place, but I can't seem to find it. (Told you I was new to this!)

 

[4pyros]

Also, Nigel (or anyone) - what is O/C ("speaker O/C")? I've looked all over the place, but I can't seem to find it. (Told you I was new to this!)

O/C = Open Circuit
Do you have a soldering iron?
The longer wire came off the choke some wrap it back on and send it thru the slot on the plastic bobbin.

 

[Osborne]

Ah - open circuit. Gotcha.
No iron, but I've wanted to get one for a while. I'm heading to Lowe's now anyway. I'll pick one up.
So wrap it back, and just solder it back on to the board where it pokes out (like the other wire)?

 

[4pyros]

yep thats it.

 

[unclejed613]

More photos (the last 6 are the most recent).
You'll see where the inductor is separated, then I seat it, then I flip the board.

There are two little nubs on the conductor that set into place on the board. Then there are two copper wires coming from it - one stubby, one long. The shorter wire looks like it should just solder to the board right where it is (that's what the smaller inductor does).
But I'm not sure where the longer wire needs to go.

View attachment 68671


Also, Nigel (or anyone) - what is O/C ("speaker O/C")? I've looked all over the place, but I can't seem to find it. (Told you I was new to this!)

the long wire continues around the inductor, and probably solders into the board on the opposite side of the bobbin to where the short wire is