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Old 30th May 2013, 05:10 PM   #1
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Default Mackie Thump TH-15a

Seems as though there's a common problem with these amp modules that can be repaired relatively easily. I'm considering buying some of these for cheap and trying to repair them myself. Does anyone know what specifically goes wrong with these (other than blown speakers)?

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Old 30th May 2013, 08:53 PM   #2
Enzo is offline Enzo  United States
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What might the "common problem" be?

As a service center, the trouble with "common problems" is that they are not all that goes wrong with a unit.

A "common problem" means that a certain something fails more often than chance dictates. What it does NOT mean is that the particular problerm happens to most of the units. Very much like automobiles. You hear that Toyota recalls several million cars because the accelerator pedal might stick. Read further to find that only a handful of the cars actually HAD the problem. SO a common problem is a matter of WHEN a failure occurs, this is a likely thing to check. That is different from THIS usually fails.

I see blown speakers in them, but then I see blown speakers in just about any PA speaker made. People think they can keep turning them up and up.

A melted speaker can then damage the amplifier section. On the other hand, and amplifier failure can melt a speaker voicecoil. When the amplifier section blows, I can pretty much count on the output transistors and drivers being history, and some resistors will be burnt open. Nothing new there.

Found some cheap? Maybe there will be just a loose connection to the AC power connector. Or maybe the amp board is burnt to a crisp, and the repair estimate was more than the worth of the speaker. There is probably a good reason they are available cheap.

The Thump 18 subwoofer is an example. When I see them, I can almost promise you the little filter card where the speaker wires connect will need resoldering on the push-on posts. But I also find them with blown amp stages, failed power supplies, blown drivers. IN short, all the things any powered subwoofer will do. Point being common problems are only one thing on the list.
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Old 30th May 2013, 11:16 PM   #3
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Thanks for the insight Enzo.

I was partially asking because I often see Flat Rate Amp Module (for this particular model) repair advertised from a reputable shop near me. This lead me to believe that the same thing must go wrong in most of them, when all it really means is that they know they can fix anything that goes wrong with them for a certain price and still turn a profit.
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Old 31st May 2013, 01:39 AM   #4
Enzo is offline Enzo  United States
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Also depends upon their flat rate. And does that include parts? They may be able to just swap out a board and make a profit. Or as you say, they just know they will average out OK. MAny problems wind up being simple. Get a hard one and shotgun it. For that matter, is that the only flat rate repair they do? Or do they have an extensive schedule of flat rates?
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Old 31st May 2013, 01:48 AM   #5
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Their flat rate includes parts... $139. I haven't noticed them advertising other flat rate services. Maybe that's their eBay sureshot money-maker....those cheap Mackies do seem to fail an awful lot.
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Old 31st May 2013, 10:20 AM   #6
JMFahey is online now JMFahey  Argentina
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Agree with Enzo (of course ) and add: I'm quite sure that a replacement module is available from the Factory for, say, U$90 ; and they probably can swap it in 1 hour or less.

Admittedly U$49 for 1 hour bench time is not exactly interesting, *but* if they have a lot of such jobs and they fill the "idle hours", well, they help to pay the rent.

One problem with the Servicing business is that it's so random and irregular.

No matter how hardworking and dedicated you are, if one given week only 2 15W beginner's amps and one toaster broke in your area, ... that's what there is baby !!!
While maybe next week an electric storm creates havoc in that same area you service and you have 60 desperate guys queuing at your door, who need things repaired "yesterday".

So those somewhat boring "replace the full board" jobs exist to even the workflow.

Now, if they had to troubleshoot at component level, cost would be much higher.

And why is the Chinese made board so inexpesive?
Among other things, consider low salaries (Guangdong Province minimum wage less than 1 U$ an hour) but much more important: robotic assembly.

Watch this mind boggling video about an automatic "pick and place" machine stuffing boards :
ACME PCB Assembly new FUJI pick and place machine - YouTube
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Old 31st May 2013, 09:18 PM   #7
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Wow. That video is something.
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