Search for: QSC K10.2 Circuit Diagram & Component Layout Overview

[klebendes_etwas]

Hello everyone! :-)

An acquaintance of mine works as a DJ in his spare time and brought me a defective QSC active loudspeaker (Model: K10.2) for repair.

Error description: The device could not be switched on (after he lent it to another DJ).

A visual inspection revealed an obviously blown fuse (F41) and a cracked thermistor (R41) on the mains filter board. A closer look at the amplifier board revealed two defective power MOSFETS (Q13, Q14) and other defective components on the +12VLOW rail.
After replacing all the obviously defective components, the device could be switched on again without any problems... but unfortunately there is no sound coming out...:-(

After a long e-mail exchange with the manufacturer's support department, I was informed that the defective circuit board would simply be thrown away. (The support employee even “kindly” e-mailed me the order form for the replacement circuit board)
For economic reasons, this approach may be plausible... but for someone like me who is just trying to fix a friend's broken stuff, it's not really acceptable...

I would therefore be interested to know if anyone knows where I can find the circuit diagram (and the component layout) for this speaker.

Thanks in advance! :-)

Kind regards

[check12]

Hmmm , there is no F41 (think you mean F4) ... & R41 is a resistor not a thermistor, so you have obvious problems in the SMPS: Q13,Q14 primary side and on the 7V and 12V rails for starters...

... but I think you will have more problems in the class d amplifier section as R41 is actually one of the two resistors in the potential divider that programmes the dead time of the IRS20957 driver IC, there is a bit of work involved in repairing this and you will need an oscilloscope etc., this is not a repair for a beginner, you won't be able to repair this amp just by replacing obviously burned out comnponents, what test equipment do you have?

[klebendes_etwas]

Hello :-)

Thanks for the reply... :-)

Hmm?
In the service manual I found online, the components are clearly labeled F41 & R41...See pictures:

Furthermore, the designation 'NTC' of R41 clearly indicates that it is an NTC thermistor...

Whatever...

I currently have: a four-channel oscilloscope (currently only 1gsa/s @ 200mhz) with a frequency generator, a logic analyzer, a bench multimeter, a nikon stereo microscope, an isolating transformer, several laboratory power supplies and so on... is any additional special equipment needed? And as for experience, to date I have carried out a wide range of repairs, from a simple class A power amplifier (Fidek) to umpteen synthesizers (Access, Korg and, my favorite so far, a Roli Searboard Grands), as well as various laptop mainboards (Dell, Lenovo, etc.).

In my opionion I now have three options to revive the device:

1. order a new circuit board (cost: €177.01),
2. reverse engineer the AMP/PSU circuit board or
3. organize the schematics, the assembly plan, etc.

Regarding 1: I would consider this if it turns out during the course of the repair that this is really the only acceptable option for reliability reasons.
Regarding 2: This takes forever and is therefore only a theoretical option.
Regarding 3: This is the only option that offers a real chance of repairing the device.

[check12]

Can't see your pictures?..🤔

[klebendes_etwas]

Can't see your pictures?..🤔

dunno...can you see them now?

[check12]

Attach the whole file or link where you are seeing that... Something is way off here...

[klebendes_etwas]

👇

[check12]

Aha ... I was looking at K10 ... I see you want K10.2 .... Here is what I have ....

[check12]

Let us know how you get on...

[klebendes_etwas]

Yay! Thank you very, very, very mutch!!!

Now that I'm finally done cataloging the defective and corroded components of a Lenovo TP480, I can spend the next few days calmly dealing with the QSC amplifier...
As soon as I've identified the fault there, I'll be happy to let you know...

[klebendes_etwas]

UPDATE:

Damn...this is going to take a lot more time than originally thought...

When i started the repair of the device, i hadn't yet bought a stereo microscope...so i just checked the board a second time visually with the microscope...and i have to say: i'm shocked! not only that the test points are already starting to oxidize...most of the components as well as some vias are in a similarly poor condition...

Fun fact: I found an old Robotron personal computer (made in the GDR in the 80s) in our garage and completely restored it... and guess what? Although the device had been exposed to decades of wetness, cold and a lot of dirt, there was no sign of oxidation on any of the circuit boards... somehow sad that today's technology no longer meets these standards... :-(

[check12]

Corrosion is common in pro-audio gear & lighting used in clubs & venues... especially where smoke machines and hazers are used as the smoke vapour gets sucked inside amplifiers etc. by the cooling fans and builds up a hygrosopic residue over time...