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THX ProMedia 2.1 light static when idle (with no sound input)


slmehl

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Hello --

Purchased at Costco; connected to Intel NUC 7i7bnh.

 

I hear light static which sounds like raindrops/clicks when the speakers are idle.
Subwoofer or Main volume controls have no effect on their loudness.

The speakers sound fine when viewing videos or just listening.

Is there a component that I need to replace to fix this?

Thanks for any information or suggestions.

L Mehl

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  • 1 month later...
  • 3 weeks later...

Hey all, I just wanted to follow up. A big thanks goes to @stpeteshepherd for pinpointing my issue with the capacitors on the AC-CD Converter daughter board, as I did fix my intermittent hissing issue! More details below...

 

With this kit being close to the cost of a mail-in repair ($130-$150 depending if you go with the kit or repair), you kind of need to weigh your own cost / benefit / abilities with a system this old. I reached out to @stpeteshepherd and decided to buy his 5.1 Ultra repair kit with a fan. My reasoning for going this route is: I have a beginner's ability to desolder / solder and have repaired this system before thanks to forum members like yourself sharing information. @stpeteshepherd has reengineered 3 components (BASH chips and AC-CD Converter Daughter board) to be cooler and longer lasting which is a godsend for a system this old with faulty parts. I also wanted a kit that had everything I needed to fix my current issue and future issues with this system without guessing, along with instructions. With that in mind, If I knew exactly what to replace, I could have bought some of the components that fixed my specific issue for less than $20, but I will inevitably have to replace/fix something in the future as these systems are prone to breaking due to heat issues.

 

Something keep in mind that as time goes on: less and less people have these systems and Klipsch Promedia electrical enthusiast may not be selling / repairing these forever, so I figured buying now is an investment in the future of these 501 Ultras 😃.

At first I sought out to do a full repair and replace everything in the kit, so I tackled the two 16v 100 uF and two 35v 100 uF capacitors at the upper right corner of the panel near the pair of small black heat sinks in the picture attached. Years ago I replaced the 35v 100 uF capacitors due to a bass hum, but I decided to replaced these with the new ones in the kit since they were and upgrade / a higher temp rating. Doing so, I accidentally pulled out a copper trace from the board because I didn't fully desolder. Stpteshepherd even warned me of this in the instructions 🤦🏼‍♂️. Re-attaching a trace is currently outside of my electrical wheelhouse, so I thought I ruined my system.  I attempted to solder the capacitor back anyways on the top and bottom of the board and it seems to be working fine, but I'm not sure if this is a permanent fix or not.

Due to this FUBAR, I decided to focus on what I believed my main problem was: The AC-DC converter board with the three 22uf 50v capacitors, 2N5551 transistor, and Zener diode on the AC-DC converter board (picture attached). I wanted to focus on this area first as this was the only area where the bottom of the board was charred. After replacing these 5 components and starting the system up again, it stopped buzzing and hissing. Once again, silence! Huzza!

Pro tips: When removing the AC-DC board, use needle nosed pliers to grab the plastic mounts under the board and unscrew the screws holding those in place on the outside of the panel. I tried to press the plastic prongs in, but the plastic is so old the prongs broke off 😑. All in all, if you are having this problem and stumble upon this forum post, doing this repair is pretty easy and even a beginner with a solder sucker and a soldering iron can pull this off.

@stpeteshepherd also gave instructions in the kit to replace many more commonly failed components and an internal fan kit to keep everything cool. Since my previous repairs are currently holding up (for now...), I didn't attempt to replace anything else in fear of causing more damage than good. I'm sure something will fail down the road, but I have the parts and instructions to tackle them when they come at me 😃.

It's crazy to think about keeping these nearly 20 year old speakers going, but they still sound great and are fairly simple to repair. I hope this helps someone in the future!

PXL_20230212_212729224.jpg

Yh1yNQC.jpg

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  • 11 months later...
On 12/22/2022 at 8:46 PM, slmehl said:

 

Hello --

Purchased at Costco; connected to Intel NUC 7i7bnh.

 

I hear light static which sounds like raindrops/clicks when the speakers are idle.
Subwoofer or Main volume controls have no effect on their loudness.

The speakers sound fine when viewing videos or just listening.

Is there a component that I need to replace to fix this?

Thanks for any information or suggestions.

L Mehl

 

Did you ever find a solution to this?  I'm having what seems like the same issue - my speakers will hiss for about 4 seconds, stop for about ten seconds or so, then hiss again, even with no source connected.  It's very quiet, and if it was consistent it probably wouldn't bother me, but as it is it's very distracting while I'm working.

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