t-amp is pushing speaker cone out

[MisterTwister]

Hello. when I connect speakers to my t-amp, speaker cones are pushed out quite a bit and stay in this position. does anyone know why this is happening?

 

[Pano]

I can sure guess! DC offset.
What can happen, and probably has in your case, it that there is a path to ground after the input caps. You do have input caps, right? There is about 2.5V on the inputs. If this gets pulled down toward ground, you'll see DC at the outputs. That DC will push your speaker cone. It only takes a small "leak" to ground to do this. Be sure there is no DC path to ground between the input caps and the chip. If the amp works OK otherwise, this is likely the problem.

Note:
You should see 1/2 the power supply voltage (above ground) on the speaker terminals of most T-amps. But you should see this on both neg AND pos terminals from ground, but not between the neg and pos. This is normal. The DC offset mentioned above is not.

 

[Poindexter]

Whut he sed.

Poinz

 

[MisterTwister]

thank you for reply.
I did modify my amp according to these instructions
http://www.diyaudio.com/forums/class-d/112395-sureelectronics-tripath-boards-2.html
removed c3 and c24. could this cause a problem?
I measured voltage across speaker terminals, it's about 1volt.

 

[cjkpkg]

yes you have DC across your speaker terminals. You should have no more than 10 or 20 mA DC on your terminals *in general*

Work from your speaker terminals backwards and the first place that DC could get into the output.

 

[Pano]

Check to see if you find about 2.5V on the volume pot or the inputs. There should not be.

 

[MisterTwister]

there was 0v on input.
oops, I just accidentally killed the amp.
shortened chip's pins with voltmeter's probe

 

[theAnonymous1]

shortened chip's pins with voltmeter's probe

Heh, been there plenty of times.