DTT2500 Subwofer not working? Dry Joint?

[newtoCaps101]

Hi Guys, So from yesterday I am trying to fix my old and reliable Creative Cambridge Sound Works DTT2500. Recently it developed a Hum that keeps growing as I increase the master volume. And the subwofer also isn't working. The Hum I think is being caused by a bad cap inside its Brick Power Adapter(?) which I plan to replace. But I cant seem t figure out why the sub isn't working.



I think its actually the AMP that is not sending the signal to the sub, because I plugged in a speaker where the sub would be and still no sound. Could it be a dry joint? or something else I should be looking for? It's dual PCB design one on the top and one on the bottom.

What do you think? anyway to fix this? really can't spend $200 on some good speakers right now.











Sorry about the bad picture quality.

[Toasty]

Re: DTT2500 Subwofer not working? Dry Joint?

Get the boards separated and get a look at, and pics of, the lower one. Note where the sub output jack traces go to, and investigate the output chip/transistors and any power resistors in that area.

The hum could be from the power pack, you're right. But getting the sub output fixed may be the answer. I've seen blown amps in a channel cause feedback/hum to the other outputs before.

[Th3_uN1Qu3]

Re: DTT2500 Subwofer not working? Dry Joint?

The hum is 100% from the power pack. Replace that bulged capacitor then worry about everything else.

[newtoCaps101]

Re: DTT2500 Subwofer not working? Dry Joint?

Okay So I just replaced the Cap on the power pack. The hum is 80 - 90% gone. I can stll feel a little bit of it when I have the speaker close to my ear. But the Subwofer, I wasn't able to figure anything out, I removed both PCB's, they both look to be in good condition, no blown caps or transistors from the looks of it.

However I didnt find any chips other than some caps and transistors on the first PCB (big one at the bottom). The top small PCB seems to have a chip or two and some shielding. But being the noob that I am I wasn't able to remove the RF/ EMI shielding, they are pretty nastily soldered! I cant seem to find a way to de solder it and take it out without using my dremel to cut it off or something.

Here are some pics. Looks to be okay, no?

the sub output lined in red. But after reading the PCB, I think the top PCB is responsible for all the outputs and processing including the sub as the audio link connector leads to there.
















Top PCB with RF/ EMI Shield












cant remove the shield

[Toasty]

Re: DTT2500 Subwofer not working? Dry Joint?

The middle one (which you haven't shown) on the aluminum heatsink is the sub amp. Please photo and report the chip number.

Leave the top board alone.

[newtoCaps101]

Re: DTT2500 Subwofer not working? Dry Joint?

Do you mean this one?


I actually thought these were some kind of "Mosfet" chips that needed to be cooled. Sorry for the bad quality but should be readable.







I also found this topic, if you scroll down to post #8. http://www.overclockers.com/forums/s...d.php?t=508585

its a guy who had similar problems with his DTT3500 (mine is DTT2500) and he somehow opened the Faraday cage / RF/EMI Shield and Exposed the ZORAN chip and replaced some caps there. So A bit confused.

[Toasty]

Re: DTT2500 Subwofer not working? Dry Joint?

TDA7360 Datasheet:



Unit has protection for "noisy" power supplies (pin 7) and it may be staying off due to that. Find the rest of the hum in either the power supply adapter(only 1 cap?) or this board. I'd start with the larger ones down the end (near fuse) as they might be across the incoming power from the adapter.

Then I would compare voltages between the 3 chips to the datasheet as a starting point.

Per Hansson from the other thread is a member here also. If he doesn't see this and pop in, I'd send him a PM.

That shield comes off with a sufficient soldering iron and some good wick.

.

[newtoCaps101]

Re: DTT2500 Subwofer not working? Dry Joint?

Thanks Toasty! So that could be it, the Power Adapter preventing the sub from working? Okay, let me try to replace that Cap again in the power supply. (yea only 1 big 6800uf 25v cap - look here https://www.badcaps.net/forum/showthread.php?t=16001)

Until a new order comes around. Where do you think I can salvage a capacitor of around 6800 uf / 25V or more? A Radio? or any other electronics I should look into?

oh and I'm no good with the soldering wick. Any tips on getting that shield out? And do I even need to take the shield out now?

[Th3_uN1Qu3]

Re: DTT2500 Subwofer not working? Dry Joint?

Let the shield be for now. Use a larger iron and a desoldering pump if you really want to see what's under it. Do you have a multimeter handy? You can make some measurements on the amplifier ICs to see whether they are working, in standby mode, or broken.

[newtoCaps101]

Re: DTT2500 Subwofer not working? Dry Joint?

I have a digital multimeter, but I dont know how to use it. no kidding ..ya i know.

its one of these stuff, I was going to ask how to use it here eventually but....


Since I dont have a second 6800uF 25V cap. Would it be possible for me to maybe rig multiple smaller 2200uf or more caps to make up for that one big cap? just so that I can test it out for now you know.

[Th3_uN1Qu3]

Re: DTT2500 Subwofer not working? Dry Joint?

Yes you can use multiple small 25v caps. As for the multimeter, ask and you shall receive: http://www.ladyada.net/learn/multimeter/

[newtoCaps101]

Re: DTT2500 Subwofer not working? Dry Joint?

Yes you can use multiple small 25v caps. As for the multimeter, ask and you shall receive: http://www.ladyada.net/learn/multimeter/

okay, most of my caps were 10v 2200uf, so let me order another 25v 6800uf cap online. its sunday here, so should take a couple of days.

I'll be baaak (says with a strong austrian accent)

[newtoCaps101]

Re: DTT2500 Subwofer not working? Dry Joint?

I'm Back! Just got my new Rubycon Cap and replaced the old one with it. taada! Now all the humming looks to be gone and my speakers and sub are working!

Thank you!


Now The only problem left is the sound / volume control knob. ( i know, knob noob_ ) When I move it to turn up or lower the volume I get some crackling noises. Sometimes It causes my subwofer to go out of sync / stop working.

Anyway I can repair the volume control knob so it doesn't make noise when moving it or interfere with the subwofer or something? thanks again!

[Th3_uN1Qu3]

Re: DTT2500 Subwofer not working? Dry Joint?

Take off the knob, spray some contact cleaner inside the potentiometer, and it should work.

[newtoCaps101]

Re: DTT2500 Subwofer not working? Dry Joint?

Thanks. Actually right after making my earlier post I did some google and figured something out. I used some mineral oil (since I dont have any contact cleaner and then moved the knobs a lot of times. It fixed the issues. So I am very happy

One last thing I noticed was a very low White noise, No hum, just a low "white noise" which gets higher as I increase the volume. when volume is in 50 - 60% I can hear it if I am close to the satellite speakers. the noise goes away as soon as I unplug the audio source. I was suspecting it was some issue with the audio source being a front panel audio port powered by onboard audio that I was using to test the thing?

[Th3_uN1Qu3]

Re: DTT2500 Subwofer not working? Dry Joint?

Yes, front panel ports are slightly noisier than the ones mounted on the rear, directly on the board. It could just be the soundcard though. Nothing to worry about, if it bothers you then it's time to get a better soundcard.

[newtoCaps101]

Re: DTT2500 Subwofer not working? Dry Joint?

Yea, I figured the same, its probably due to the onboard audio and front ports I am using to test it lol. But I think I have a good sound card (onboard) though on the PC I want to use it on so hopefully it will be just fine.



Thanks for all the help uN1Qu3

[newtoCaps101]

Re: DTT2500 Subwofer not working? Dry Joint?

Yes, front panel ports are slightly noisier than the ones mounted on the rear, directly on the board. It could just be the soundcard though. Nothing to worry about, if it bothers you then it's time to get a better soundcard.

hey uN1Qu3, Toasty; after months of service the thing is starting to act strange again.
I started a new topic: https://www.badcaps.net/forum/showthread.php?t=18833
Some help please guys?

[anthonyd]

Re: DTT2500 Subwofer not working? Dry Joint?

My unit works fine except for occasional intermittent drop in audio about 50-70%, very annoying. The signal from computer doesn't drop but both satellites and woofer drop the same. Tapping board, signal input plug 1/8" not the cause. I hand soldered the complete board and problem still there, I use a different PS 3amp 12volt and tried different ones. It seems like it would be a cold solder joint but that's been ruled out, if it was the driver IC it would not occur on both satellite and woofer. Perhaps in the input preamp stage? Anyone with that problem?? Also, ruled out the potentiometer control. Thanks for any help.