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.
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.
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:
You could have a transformer that's intermittently shorted.
The diodes behind the terminals are likely transient voltage supressors. Examples:
http://datasheet.octopart.com/1N6293A-E3/54-Vishay-datasheet-565176.pdf
The diodes behind the terminals are likely transient voltage supressors. Examples:
http://datasheet.octopart.com/1N6293A-E3/54-Vishay-datasheet-565176.pdf
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.
Would this contribute to an upgraded amplifier?
Arrow sells the STP80NF10 for ~$1.40 and is convienient to my current shopping cart.
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?
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.
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.
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.
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.
The drive signal on the fets with +10vDC gate are traced through 10ohm resistors and directly into pin 7 of the 8 pin IC labeled MIC 4424CN
http://www.micrel.com/_PDF/mic4423.pdf
Just confirmed the MIC4424 is bad from this datasheet; INA -> OUTA and INB -> OUTB. INA signal looks alright but OUTA is bad. INB/OUTB look good. This IC needs to be replaced.
Just wondering though... Could I clip pin 7 and tie pin 5 to pad 7 to continue testing this amp or would I be asking for trouble?
Just confirmed the MIC4424 is bad from this datasheet; INA -> OUTA and INB -> OUTB. INA signal looks alright but OUTA is bad. INB/OUTB look good. This IC needs to be replaced.
Just wondering though... Could I clip pin 7 and tie pin 5 to pad 7 to continue testing this amp or would I be asking for trouble?
No but you can remove the IC and solder jumpers from the input to the output. Don't try inserting wires into the socket. You may deform the contacts which could result in reliability issues.
Cool I did that and am able to get some power flowing through this amp with a couple of IRF3205s.
I think I found the ultimate problem; a short on the leg of the transformer. I'll have to get an insulator in there, but for now I was able to slightly move the winding so it was out of being shorted. Referencing amp general ground, the center leg of the rectifier D12 (pictured) is measuring 110vDC.
You can see the short in this photo:
I think I found the ultimate problem; a short on the leg of the transformer. I'll have to get an insulator in there, but for now I was able to slightly move the winding so it was out of being shorted. Referencing amp general ground, the center leg of the rectifier D12 (pictured) is measuring 110vDC.
You can see the short in this photo:
Now I dont understand one thing. One power supply in this amp is creating 110vDC on the center leg of the rectifier, and the other power supply is making 81vDC.
While powered the amplifier stays out of protection. It is holding power now.
While powered the amplifier stays out of protection. It is holding power now.
Maybe I get it now but dont know why - the PS making 110vDC on the center leg of rect appears to be running unregulated. The PS pushing 81vDC on the center leg of the other rect appears to be regulated.
I know why. In testing the PS i this amp, I've only been testing one supply at a time. When both sets of PS fets are installed, both rect center legs measure 81vDC. If I remove all fets from Q12/13/14/15 then the remaining PS measures 110vDC center of rect and the waveform on legs 1&3 of rect is square.
I think I'm alright here. With all fets installed the PS looks good.
Theres a small blue rectangular pot in the center of this amp. Is this the adjustmentt for rail voltage?
This amp runs positive rail voltage, which means referencing amp ground the speaker terminals have +40vDC on them. I guess that means the same for the opAmp which only has +13vDC and 0vDC on power pins. Opamp outputs have 6vDC on them. Supply voltage seem to be a little low (+-6vDC)?
I think this amp will be repaired once I get replacement parts: MIC4424, two diodes, insulator for the transformer, and fresh IRF3205s.
Thanks!
I think I'm alright here. With all fets installed the PS looks good.
Theres a small blue rectangular pot in the center of this amp. Is this the adjustmentt for rail voltage?
This amp runs positive rail voltage, which means referencing amp ground the speaker terminals have +40vDC on them. I guess that means the same for the opAmp which only has +13vDC and 0vDC on power pins. Opamp outputs have 6vDC on them. Supply voltage seem to be a little low (+-6vDC)?
I think this amp will be repaired once I get replacement parts: MIC4424, two diodes, insulator for the transformer, and fresh IRF3205s.
Thanks!
Last edited:
The pot may be to zero the DC offset.
The op-amps that drive the 4080 are generally biased to 6v.
The op-amps that drive the 4080 are generally biased to 6v.
- Status
- Not open for further replies.