Klipsch pro media 2.1 system - he no workee. man cries. - diyAudio
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Old 7th February 2013, 11:29 PM   #1
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Location: United Kingdom
Default Klipsch pro media 2.1 system - he no workee. man cries.

So I've acquired some Klipsch pro media 2.1 which are apparently not working (nothing heard out of any of the 2 speakers or subwoofer) ....whipped the backplate off - nothing scorched inside (always a plus), so now want to start troubleshooting.

I'm figuring here that since there's neither speaker working nor the sub, that it's likely a power supply fault or a preamplifier fault.

Here's the whole list of internal module schematics...

New Version Klipsch Promedia V2.1 Amplifier Repair

& here's the actual power supply (click to enlarge)...

Click the image to open in full size.

Explanatory words of the wise here...

Quote:
"The AC mains voltage passes through a small line filter and is then rectified to give approximately 340 Vdc for primary-high. Leaving off J9 configures BR1 for bridge rectification when the AC mains are 240Vac; stuffing J9 makes the bridge act as a voltage doubler when the AC mains are 120Vac, and gives the same approximately340Vdc. Primary-high is stored on a pair of series 200V electrolytic caps.

Resistor R7 and D1 deliver the initial voltage from primary-high to turn on the controller, U1, living on a daughterboard. Transistor Q2 and ZD2 form a discrete regulator to power the controller IC. Diode D4 prevents backwards current from flowing into the regulator. Once power is applied, U1 generates a 50% clock set by R21 and C28. Each clock state generates a high pulse on HO or LO, the isolated gate driver outputs, with a fixed deadtime inserted between pulses. This simply alternates turning on the two half-bridge transistors. Diode D8 and C22 form a bootstrap circuit to turn on the upper FET, recharging the cap when the lower FET is on.

The switched-mode power supply (SMPS) on the main SMPS board is a simple half-bridge, resonant, unregulated circuit. Each gate drive output goes through a gate resistor with ananti-parallel diode. The FETs, Q5 and Q7, alternately turn on, chargeing and dischargeing the transformer primary winding, T1:1. The resonant action of the supply is created because the current through the transformer primary must flow through either C3 or C5. This creates a square voltage waveform across the transformer primary with a sinusoidal current. This supply is very efficient as it uses zero current switching to (nearly) completely avoid switching losses. It's also excellent for audio applications because the lack of regulation isn't a detriment in the face of the high crest factor of audio signals. Finally, the square voltage waveform provides consistent, reliable output voltage.

During normal operation, T1:2 also gives a square voltage waveform which is rectified by D3 to supply the controller with operating voltage, relieving R7 of this duty.

Each secondary winding (T1:3 and T1:4) uses dual series rectifier diodes to bridge rectify the winding's voltage waveforms into a stable DC voltage. A small inductor filter reduces noise"


I'm figuring the CN2 connector voltages (+39V & -39V) & CN3 connector voltages (+27V & -27V) are the first port of call for troubleshooting? (just got to rig this up to 110V AC....cos I'm located in the UK & our wiggly volts are bigger than your wiggly volts)

(don't be alarmed...I do realise there's some chunky DC voltage (300V+ on C2+ to ground) on that SMPS so I'll proceed carefully!

Last edited by peskywinnets; 7th February 2013 at 11:37 PM.
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Old 17th February 2013, 07:48 PM   #2
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Well after all that, it was just a fuse! (albeit a fuse that didn't look like a fuse .....& a 'leaded' fuse soldered thru hole to the darned pcb).

Looks like the previous owner has plugged a 110V device into 240V ...erhmm, pop.

So I simply applied 110V to teh PSU input after the blown fuse (via a step down transformer mains lead that was in itself fused) & the unit sprang into life.

Bit of a result ...picked this thing up quite cheaply.
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Old 22nd February 2013, 11:12 PM   #3
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Default Klipsch Promedia 2.1 to 3-channel mod

Very nice. Tinkering with one of these systems is what got me into DIY audio junk. If you have a need for bass and a subwoofer output on your music source (I presume it is a PC), you may want to turn your 2.1 channel setup into a 3.0 setup.

Right now, a low-pass filter in the control pod is separating tones of <80 hz and directing them to the subwoofer amp. You can circumvent this filter and feed the subwoofer amp directly from the sub out port on a sound card. Creating the low tones for the sub with software, instead of circuitry, gives you much more control over crossover frequency and thumpiness.

I've got mine relayed through a toggle switch so that I can switch between the 3.0 and the 2.1 methods. If you were able to find and replace that fuse, you'll have no problem with this. Let me know if you're interested, I can post some pictures for you this weekend.
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Old 27th September 2013, 01:16 PM   #4
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Quote:
Originally Posted by peskywinnets View Post
Well after all that, it was just a fuse! (albeit a fuse that didn't look like a fuse .....& a 'leaded' fuse soldered thru hole to the darned pcb).

Looks like the previous owner has plugged a 110V device into 240V ...erhmm, pop.

So I simply applied 110V to teh PSU input after the blown fuse (via a step down transformer mains lead that was in itself fused) & the unit sprang into life.

Bit of a result ...picked this thing up quite cheaply.

Hope you don't mind me bumping this thread.

I am over in the UK also and got the pro media from the US which was plugged into the 240 and "POP" :-(

I took out the PSU and can see firstly that the T2A/L250V Fuze is open.
Also one of the Caps may be gone (top is a bit bubbled).

I tested all the diodes and regulator BR1 and they all look ok.
I'm hoping that just these 2 components were damaged.
I see there is a link on the board called J9 and it says "Remove to r240v".
Has this anything to do with converting the PSU to a 240 input.

Anyway if I get a 240 to 110 stepdown converter at the same A rating should this be ok?

Many thanks for the advice.
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Old 27th September 2013, 03:14 PM   #5
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The schematic show a jumper which should be removed for 240 volt operation. Does your PS have such a jumper?
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Old 27th September 2013, 03:57 PM   #6
AndrewT is online now AndrewT  Scotland
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first power up via a bulb tester would have saved the fuse and the other damage.
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Old 27th September 2013, 04:19 PM   #7
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Quote:
Originally Posted by Frank Berry View Post
The schematic show a jumper which should be removed for 240 volt operation. Does your PS have such a jumper?
Hi Frank,

Thanks for replying.
It does have a wire link canned j9. So is it a case if cutting the link for 240 volt operation?
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Old 7th October 2013, 12:51 PM   #8
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I have removed J9 and ordered replacement fuse and caps. Will test then off 240v and will post my results here for anyone else that may want to do the same.
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Old 11th October 2013, 03:58 PM   #9
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Quote:
Originally Posted by paulod View Post
I have removed J9 and ordered replacement fuse and caps. Will test then off 240v and will post my results here for anyone else that may want to do the same.
Success. Replaced the Fuse and Capacitor. Removed J9 and hooked up to 240V.
Everything working nicely.
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