MMATS DHCX2200.05 Issue - diyAudio
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Old 9th March 2013, 05:44 PM   #1
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Default MMATS DHCX2200.05 Issue

the outputs were totally blown up, but the power supply was fine.

So i replaced all the ouputs, and changed the HIP4080.

It powers up, but it just ticks. hear the ticking in the speaker. No sound. If i turn the gain up, it starts to sound like running/revving engine and eventually the amplifier actually "barks" through the speaker and shuts off. And starts ticking again.

I have no idea. where to look now. Maybe the ramp oscillator? any ideas?
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Old 9th March 2013, 06:52 PM   #2
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It used P80NE0 for outputs, I had IRF3415s on hand and a HIP4080 on hand, I used those. I have used IRF3415s in other HIP amps without issues, Would this be a problem in this amp?
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Old 9th March 2013, 09:48 PM   #3
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The 3415s were a good choice before the IRF3710Z was available. The 3710Z is rated higher (current) than the 3415 so it should be more likely to survive.
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Old 9th March 2013, 11:09 PM   #4
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Well this thing blew itself up in my face again trying to find the fault. lol. So I gotta order all new FETs and 4080 again. AWESOME....

looks like im going to shotgun it and replace the 3525, and all the op-amps as well just to make sure.

I noticed the white noise/motorboating sound with ticking/phasor noise goes totally away if i heat the op-amp area with a heatgun. But ALL sound goes away. no audio.

BTW theres no audio or any presence of audio during the "freaking out" of the amplifier. Also the gain affects it. I can remove RCAs, and just turn the gain up and itll go into that freakout mode. If i turn the gain all the way to 0, it just ticks with an audiable pop-pop-pop-pop from the speaker.

Both the inverting and non-inverting input of the SG3525 are at 5V. The power supply will burst with gate drive for a short duration before going flat, every time it ticks. Its in sync with the output devices as well. For whatever reason, the amplifier output stage will not run. Fault LED is OFF. Power LED is on.

I might shotgun the caps too. I dont know yet. The output filters appear fine, bending/twisting the inductors make no change.

Pin 6 of the HIP4080 had a nice stable sawtooth wave on it. Pin 7 had a low level state, that was jumping around during the ticking. When the amplifier would go into its freak out mode, this pin contained a totally erratic oscillation waveform that was all over the map.

I looked at the 3710, its a nice transistor, also cheaper. BUT it gains more current at the cost of voltage. i noticed its 50v less than the 3415 counterpart.

Last edited by mbates14; 9th March 2013 at 11:20 PM.
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Old 10th March 2013, 12:23 AM   #5
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The rail voltage can't be higher than the voltage of the 3710Z because the IC is only rated for 80v.
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Old 10th March 2013, 12:56 AM   #6
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Makes sense. Im thinking in terms of usage in other amplifiers. Just deciding to see if i wanna stock those instead of the 3415. Because right now, I stock TIP35/36, 3205, 3415, and P064s regularly.

Pertaining to the MMATS issue, I think it might be in the analog section. Having a nice sawtooth in the + input of the HIP4080's comparator, and having something indeterminate in the negative input means the "sound" i hear is real sound but coming from the audio preamp section.

Last edited by mbates14; 10th March 2013 at 01:20 AM.
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Old 10th March 2013, 03:04 AM   #7
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IIRC MMATS had nothing but issues with the lines built around that driver IC. Then again, everyone that used it kinda sorta had nothing but issues.. LOL. I had a few here and hated them. I ended up making some modifications to one of them and I found out the hard way I got a bad batch of HIP4080's as well. In fact, don't rule that out as they had similar results to your issues. Also the output gates need to be as close to original as possible and that presents some issues as even matching the original part numbers just doesn't guarantee it. The whole damn idea was a mess and an amplifier should have never been designed around it. I looked over the application notes on that chip and it would seem that some manufacturers flat out ignored them at times. Good luck with that thing.
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Old 10th March 2013, 03:50 AM   #8
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Strange though, I never had issues with any other HIP based amplifier. It must be this design. And not so strangely, I cant find a schematic on this thing either. Anyway, I appreciate the help. Thinking i might disconnect the analog stage and trace it a block at a time.

EDIT: Original FETs are P80N06 i think. which is 3660pf gate capacitance, the 3415 is 2600pf.

Edit 2: I had noticed depending on the manufacturer of the P80N06, it varies alot...

Last edited by mbates14; 10th March 2013 at 04:18 AM.
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Old 10th March 2013, 04:11 AM   #9
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You won't have clean audio going into the 4080. The op-amp used for feedback compensation constantly modifies its output to make the output at the speaker terminals clean.

The 3710Z is the only transistor that I've found that works properly in virtually all of the 4080 amps. There are likely to be better FETs on the horizon but I haven't found any yet.

When the output FETs are incompatible, it can cause all sorts of problems. If you have an amp that you want to use a particular FETs in but you're having problems, install a full set of 3710Zs. If the amp works flawlessly, you know that the problem is almost certainly the other FETs. If it doesn't work with the 3710Zs, you need to do some more troubleshooting. If you find that there is a problem and you can get it to work with the 3710Zs after you repair that fault, then you can go back to the other FETs to see if they'll work.
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Old 10th March 2013, 05:42 AM   #10
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Well i gotta order all new FETs and a new 4080 anyway, so i might as well grab some 3710s. Plus they are cheaper, i order all my stuff from digikey. I also noticed this amp does not use split-rail system either. And none of the op-amps are split rail. They are +10V (thats what i read) and GND.

Last edited by mbates14; 10th March 2013 at 05:46 AM.
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