So I just had a return from an eBay sale on an MTX RT1000D, which apparently shorted a 3205 in the power supply for no apparent reason. This was a S-D short, and it had to have happened at low/idle power since the case of the device was still in perfect condition. Typically if they fail at high power they blow the case apart and melt stuff, this one I didn’t even notice till I put a meter on it. These all came from the same batch, out of the same stick from mouser. Anyone else having reliability issues out there amid this semiconductor shortage?
Can you be more specific about the situation? From what I understand you bought components from Mouser, used them in a product and you sold that product to a customer who then returned it defective?
Correct. Initially I assumed the worst and figured it was abused or a board swap attempt, but after inspection it became clear the device failed on its own for no apparent reason. Never before have I had issues with properly sourced semiconductors, but in light of what’s currently happening in the industry I’m beginning to wonder if there are QC issues beginning to manifest. The 3205 is pretty ubiquitous in car audio, they crank these things out by the millions so there’s bound to be a few bad apples in a basket so to say. I’m just wondering if anyone else had a similar experience because if so I may change vendors or look for similarly rated parts from producers other than international rectifier, the margins on these repairs is already razor thin- I can’t have returns on these items for obvious reasons.
Does this amp use the MTX type driver transformer?
When FETs fail, they generally fail G-D for one FET. This turns the entire bank on which causes high current, no matter the power level at the time of failure.
Was that single shorted FET causing the fuse for the amp to blow?
I've use many 10s of thousands of semiconductors and have found essentially no defective semiconductors from authorized distributors. Others may have different experiences/opinions.
There could be intermittent problems like bad/broken connections on the gate resistors. I've also seen cracked Cts or bad connections on the Ct on the PS driver IC to cause power supplies to fail.
When FETs fail, they generally fail G-D for one FET. This turns the entire bank on which causes high current, no matter the power level at the time of failure.
Was that single shorted FET causing the fuse for the amp to blow?
I've use many 10s of thousands of semiconductors and have found essentially no defective semiconductors from authorized distributors. Others may have different experiences/opinions.
There could be intermittent problems like bad/broken connections on the gate resistors. I've also seen cracked Cts or bad connections on the Ct on the PS driver IC to cause power supplies to fail.
Replace the mosfet, and see if it stays fine. It could be a variety of things, but for now it's best to assume it was a one time incident.
If it keeps happening to the same mosfet, then I would start looking at the reason the mosfet blew in the first case when it came to you for repair. It may have a faulty drive circuitry component that only starts acting up when used for a while (heat, etc)
If it keeps happening to the same mosfet, then I would start looking at the reason the mosfet blew in the first case when it came to you for repair. It may have a faulty drive circuitry component that only starts acting up when used for a while (heat, etc)