Factory Modded Older MMATs 1200w Class D - diyAudio
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Old 11th April 2011, 04:16 AM   #1
Dr Zeus is offline Dr Zeus  United States
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Default Factory Modded Older MMATs 1200w Class D

I think this amp is a D300HC. Check out the 12,000uF cap attached to the PCB - I'm told this is a factory modification. The amp is stamped with year 1999 rev 8F on the board as well. This is only the second Mmats amp I've had to look at and the first malfunctioned amp was never repairable.

Click the image to open in full size.

This is the second time I've seen this amp on my bench. The first time, I could not find anything wrong with it so I gave it back to the customer free of charge. Less than a day later, he calls me and said it created fireworks in his trunk! When I asked what size fuse he has, he told me his breaker up by the battery was 250A and it never blew.

The entire PS is blown in this amp which uses P80NE0 built by ST. It appears that only Quest Components has the P80NE0 in stock, but I need to be careful here because the part number seems to also be bringing up a 30V 80A fet. I believe I need a 60V 80A fet. A few rectifier diodes behind the battery terminals also split in half and I think they are "18A 0217".

The outputs seems to be OK, this amp using IRF249H.

What else would have caused this amp to go and blow up is beyond me. The owner said he ran it under an 8 ohm load but I really have my doubts. Who runs 8 Ohm load anything??? lol.

Last edited by Dr Zeus; 11th April 2011 at 04:18 AM.
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Old 11th April 2011, 04:44 AM   #2
Dr Zeus is offline Dr Zeus  United States
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STP80NE06-10 appears to be the correct part for the PS in this amp.
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Old 11th April 2011, 04:45 AM   #3
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You could have a transformer that's intermittently shorted.

The diodes behind the terminals are likely transient voltage supressors. Examples:
http://datasheet.octopart.com/1N6293...eet-565176.pdf
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Old 11th April 2011, 12:59 PM   #4
Dr Zeus is offline Dr Zeus  United States
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I'm having trouble sourcing STP80NE06-10 anywhere except on ebay.uk.co. Funny thing is while looking on ebay, I found STP80NF10. Could it be a suitable substitution? The stats look quite similar with the later having a rating of 2x the wattage output (300w on the F10 vs original 150w on the NE06).

Would this contribute to an upgraded amplifier?

Arrow sells the STP80NF10 for ~$1.40 and is convienient to my current shopping cart.
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Old 11th April 2011, 05:27 PM   #5
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I generally use IRF3205s in these amps.
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Old 12th April 2011, 04:31 AM   #6
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what is the voltage rating on that external capacitor?
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Old 12th April 2011, 04:55 AM   #7
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80v
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Old 16th April 2011, 04:11 AM   #8
Dr Zeus is offline Dr Zeus  United States
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Now that I've taken this amp apart a bit, I notice the diodes behind the power terminals have markings: PK 1.5KE 18A 0217. Obvious these are 1.5KE and the 18A rating is 18v?
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Old 16th April 2011, 04:25 AM   #9
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There should be another row of numbers on the TVS.
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Old 16th April 2011, 05:01 AM   #10
Dr Zeus is offline Dr Zeus  United States
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OnSemi PK 1.5KE 18A 0217 is all that is on the diodes.


I removed the failed diodes at D22 and D28 which previously cracked right in half. Also noticed the 10ohm resister in close proximity was chipping away, so I just replaced it (Green resistor now). Also note power terminals are removed for easier work space.

Click the image to open in full size.

I think even with these two diodes removed the amp is still able to partially power up. Upon applying power, the amp trys to come up but within 5 seconds goes into protection. While starting to come up, I am able to survey voltage and wave form at the power supply fet gates. Half the fets receive a very clean +10v square wave, while the other half are measuring almost a perfect +10v straight DC signal.
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