Originally Posted by RDKing2
I did not pull it from the board yet. No longer reads short to ground on any legs with bad transistors lifted, was showing short to ground at all legs. About 57ohm across outer legs, open from center to either outer leg.
Have been feeling a bit weird posting in the thread about my (amplifier) woes. Was hoping some may be interested in fixing their own. Thanks for letting me know.
BTW, late last night as I was drifting off it popped into my head as to why I purchased the 14k. I originally was running one EPX4000 on each of my LMS Ultra's. One stopped working. Cannot remember if it was the same sub. I did ohm out the subs today and both are just above 4ohm. Do you think it is worth the trouble to pull the one that was on the bad channel, disasemble the driver and do a visual?
There are 2 things I think about when an amp fails as yours did:
1) Heat, especially if the fans were modded to give 1/2 the air flow or if the amp is in an enclosed space, etc.
2) Bus pumping when the amp has been operated in 2 channel mode. This is probably not a problem for a real Lab-type amplifier, but certainly something to consider using a lesser cost option, especially considering the application, which includes single digit signal at high levels.
Bus pumping occurs with low frequencies and specially so with ultra low frequencies. I've had several big iron amps cry uncle with WOTW at reference level. It can also cause components to heat to a destructive point in a heartbeat.
Another cause is very low impedance. I'm not convinced that impedance is a simple thing to measure and that includes impedance sweeps done with DATS or REW. So, yes, if it were me, I'd certainly have a look at the driver in question. I would not want to get a new board and repair the amp and have the same thing happen again.
Finally, a problem I've been looking at is the PS caps not having enough sink capacity, which would definitely be a problem with bus pumping, especially since I was given the following heads up regarding low cost amplifiers...
Amazing. I'm not saying this amp has that problem but the picture shows that the problem exists.
I don't know how to measure the values of a cap. If anyone can help out here, I'd appreciate it. I do know that the Asian amp build houses buy the lowest price, most readily available caps when the need them. From amp to amp, the cap brand has never been the same twice. If the amps were tested before leaving the factory, a problem like crap caps would show up and be dealt with before it got to you, but I pretty much bet it ain't happenin and won't happen. So, I'd prefer to check them myself, I just don't know the proper procedure and the best tool to use?