My 50W, 8ohm amp can't drive my 86db, 4ohm speakers? WTF??

tboooe OP957 posts03-26-2016 11:10amLooks like my Accustic Arts integrated amp is repaired.  The parts that failed were:

1) $83.99 - 15V Regulators
2) $49.60 - Rectifier

Total bill with labor came out to around $500.  Ouch!  However, its a lot less than buying a new integrated amp.  Hopefully this repair will keep my amp chugging along for at least 2-3 more years!  Then I think I will step up to a tube integrated!

As I am no electrical engineer I am not sure what these parts do and if these are common failures in amps.  I am just happy to be able to listen to my system again soon!

wow! is that true - that's what was broken?? I'm surprised....

both parts related to the power supply.
A regulator is an electronic ckt that ensures that a steady 15VDC is output to the electronics its supply power to. Steady in the sense that the peak-peak ripple is kept as low as possible, good line regulation i.e. if the incoming power supply to the 15V regulator fluctuates a bit, the output 15V is held as steady as possible under those circumstances, good load regulation i.e. if the client electronics ask for more current, the output 15VDC will not sag voltage-wise.
I'm just wondering how a 15V regulator can fail? It's under-spec'd for the client electronics it supplies power to, an AC voltage surge during a bad electrical storm (that would take out more elements in the power supply elsewhere in the power amp), some ancilliary component failed (like a decoupling cap or a bias resistor, etc) that caused the 15V regulator to malfunction momentarily & fail.

A recitifier is also part of the power supply that converts incoming AC sinusoidal voltage to a DC voltage (with a large amount of ripple, which is eventually reduced/eliminated by those large coke-can power supply capacitors). Recifiers are essentially diodes - sometimes/often high-speed diode known as FREDs or Fast REcovery Diodes - which are often rated for high current (60A, 100Am, etc) & high-speed operation. The need for high current comes when you 1st switch on your power amp - there is a surge of current required to charge up those coke-can & other power supply capacitors. This surge lasts for 2-5 seconds depending on the amount of capacitance & it all has to flow thru the recifier. For example, my amp when 1st turned on takes 37A per channel for those 2-5 seconds.
Again, I'm wondering how a rectifier can fail - it's under-spec'd for the job, an AC power surge during a bad electrical storm, power supply capacitor does not have a DC path to ground to discharge when the amp is turned off thus discharges thru the rectifier diode (bad design) or failure due to age i.e. fatigue due to repeated on/off cycles - for this amp has to be really old. Even then, i dont believe this - my 1977 Yamaha integrated is working with its original rectifier diodes. The power supply caps were changed, of course, due to age of the unit.
Hmmmmm.....unless there is a good explanation for the failure of these 2 power supply parts, there's something fishy going on in your integrated amp unit. I'd keep a close watch on it. If these parts failed due to an anciliary part failing & that anciliary part was not replaced, you run the risk of having the exact failure repeat over time.... FWIW.

Thank you @bombaywalla for the detailed response. I really appreciate it.  My amp is about 5 years old so I am surprised this happened.  I have asked the technician for a more detailed response on exactly what the issue was and what the thinks caused the failures.  I have my integrated amp plugged into a PS Audio P3 AC regenerator that also acts a  surge protector so it should have protected against spikes.  I guess it could I got some faulty parts when the unit was manufactured.

Good to hear you'll be up and running soon......my system was in storage for  months after we had a pipe break upstairs and damage two rooms, one of which my system was in.....listening to a mini system was rough for that amount of time.

Again, I'm wondering how a rectifier can fail - it's under-spec'd for the job, an AC power surge during a bad electrical storm, power supply capacitor does not have a DC path to ground to discharge when the amp is turned off thus discharges thru the rectifier diode (bad design) or failure due to age i.e. fatigue due to repeated on/off cycles - for this amp has to be really old.

Shorted power rectifiers are a common problem in many amps. There is nothing surprising about this, nothing to do with any of the issues you mentioned (although they can be influences). Sometimes they just fail for no reason. 

I wonder if turning on and off my amp daily had a part in this.  I think I will consider leaving it on all time, though I really dislike that thought since I only listen to my system 1-2 hours a night.