draining battery

Unregulated power supplies are usually set at 50 percent ('ON' 50 percent of its timing cycle) and don't suffer from lower voltage. A regulated supply will try and compensate for the lower rail voltages and increase the 'ON' time which as csound stated increases the current and heats up the mosfets. The heat protection circuit is 'supposed' to shut the amp down before damage occurs, but more often than not, it doesn't. I had someone bring me an old Coustic 380 to repair that had an output transistor shorted out. This amp got so hot that the paint bubbled-up and the protection circuit never shut it down, nor did it blow the 30a. fuse.

Just curious. Wouldn't low voltage cause the remote on lead to shut the amp off?There is no such thing as free installation!

If it is agreed that the power supply will have to supply more current when the signal is clipped, then it doesn't really matter whether the power supply is regulated or not. Still more current has to flow and causes for heat generation and eventually breakdown.Marius Minnie

 An unregulated PS is 'usually' running on a 50 percent duty cycle and will/should handle more load due to the constantly drained rail capacitors. Its the regulated PS's that will suffer the most. Yes, unregulated PS will run hotter due to lower supply voltage, but my experiences lead me to believe that they survive low voltages better...within reason.

Thank you "dboomer". Seems you have enough experience with amplifier repair. Please have a look at the pictures on the link below. (you have to copy and paste into your browser) What could have caused this damage to the power supply? No obvious reasons inside the amplifier could be found. This amplifier has a dual power supply and both went up in smoke. No output transistors were blown. www.freewebs.com/autoaudiorepair/mig1500.htmMarius Minnie

How many ohms are your speakers drawing? Ususally damage to both supplies is caused by running to many speakers wired in parallel. The weakest mosfet will short out internally and take-out the others. Also check your rail capacitors and rectifiers for shorts. It doesn't take much of a load/short in the secondary winding of the transformer to make a huge load in the primary and may not show any signs of damage.

2 x SVC 800W Kenwood subs = 2ohm. The amplifier is 1ohm stable. Both torroidal transformers are secure and OK, dual diodes and caps tested OK. Marius Minnie

It could be that steezs' amps have low voltage protection, looks like the acoustik and hifonics brands are manufactured by reputable companies. This amplifier was manufactured in China and, as far as I know, does not have any low voltage protection. I think that the poor ground that dboomer mentioned is a definite cause for power supply failure but it was not the cause in this instance. I had a look at the power cables in the clients' car, it is wired with 4guage cable (power and ground) with good, clean connections. So, to get back to the original question, can the power supply be damaged by fading battery power (amp without any low voltage protection), taking into consideration the load and initial setup voltage?Marius Minnie