Diamond D7104 static through one channel? - diyAudio
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Old 3rd October 2012, 08:27 PM   #1
diyAudio Member
Join Date: Aug 2012
Default Diamond D7104 static through one channel?

So I bought a Diamond D7104 from someone a while back, 3 channels worked and 1 did not.

Had a EE friend look it over. He found a coupling cap had fallen out, he soldered it back in, and completely recapped the whole thing.

He put bigger caps in as well in a few places.

"You can see the bus bars over the caps, really stupid design, and they all used to be 470uF sized, the same as the 2 that are under each bar which still are 470uF, new, but same size. I went with 1000uf for the rest of them since the room was there and with car amps and capacitance the more the better, to a point. That changed the storage there from 9400uF to 16940uF, or 1.8 times larger. These are the input DeCoupling, they do the same thing adding in some huge Farad cap do, just not to that extent, but increasing the value never hurts.

The 6 large caps there, technically 3 when it showed up here since they were all broken off, were originally 1000uF each, and are now 2200uF, so an increase from 6000uF to 13200uF, or 2.2 times larger there. Those are the DeCoupling caps for the higher voltage the power supply makes for the amplification."

I got the amp back yesterday and got it installed. First thing I noticed is that its beautiful, and this thing has a TON of power.

After some listening, the amp sounds great. Havent tested channels 3/4 yet, but 1/2 work good.

The only issue Im having, is that the amp is making erratic static noises coming through channel 1. They are going through my passive x'overs in my doors and I can only hear them coming out of the tweeter. If I crank the volume up, you can no longer hear it. It is not doing this on channel 2, and if I unhook the RCA cables it still does it. Power/ground connections are very secure.

Any ideas as to what could be the issue? Like I said, for right now, the amp works great, it just makes quite a bit of on and off static through one channel.
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Old 3rd October 2012, 09:19 PM   #2
diyAudio Member
Join Date: Aug 2012
I just checked. RCA shields on amp are not shorted. Both measure 92.3 ohms on my meter. Checked all 3 other channels as well, none make the noise except for Channel 1. Tried played with the crossover functions/gain knobs/etc to no avail.

There was a coupling cap that fell out inside the amp which caused one of the channels to stop working. I dont know which one it was, but my money is on channel 1. The coupling cap was still inside the amp, so he just soldered it back in.

The amp works great as far as I can tell, the static coming through is a bit annoying at low volumes though
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Old 5th October 2012, 01:59 AM   #3
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Join Date: Nov 2003
Location: Louisiana
If some of the failed capacitors leaked electrolyte onto the board and the electrolyte was not cleaned up properly, that could cause noise.
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Old 5th October 2012, 07:11 PM   #4
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Join Date: Aug 2012
Perry, none of the caps had actually failed yet, we just replaced them in fear that they may soon.

Do you think the cap upgrades my friend were minor enough for the amp still function normally? It is working great right now, just makes a slight "pop" through channel 1 when it turns on, which is the same channel that makes a staticy noise. Does that help narrow it down any?
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Old 8th October 2012, 01:57 AM   #5
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Join Date: Nov 2003
Location: Louisiana
Check all of the op-amp output pins for excessive DC voltage. None should have anything greater than 0.01v DC. Place the black meter probe on one of the non-bridging terminals when measuring the voltage.
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