Fault must be in preamp, I got it wrong! TEAC A-H300
Mar 01, 2010
- I have screwed up! I have reconnected all plugs and sockets and stood the pre amp board on end so I can get to both sides. I then applied a signal to the main amp input socket, that works OK up to the cut out relay with plenty of level, the relay remains off. If I trace the signal from any input, I loose it very quickly, the selector switch makes no difference and there is a leaky signal that can just be heard at the loud speaker if I overload the input. So a major fault on the pre amp, not the power amp!
- I have screwed up! I have reconnected all plugs and sockets and stood the pre amp board on end so I can get to both sides. I then applied a signal to the main amp input socket, that works OK up to the cut out relay with plenty of level, the relay remains off. If I trace the signal from any input, I loose it very quickly, the selector switch makes no difference and there is a leaky signal that can just be heard at the loud speaker if I overload the input. So a major fault on the pre amp, not the power amp!
Audio Players & Recorders - Teac - A-H300 Amplifier
Answers & Comments
Just curious, what preceded this? Sudden spontaneous failure with no manual action associated? Is the Tape Monitor activated?
I don't know how valuable your speakers are but you're hitting them with max power and distortion when you get that bang. I'd use cheap headphones for the troubleshooting phase.
Can't help you much more on the troubleshooting but if you think a 30-watt amp can't blow up a 50-watt speaker you are mistaken. Under-powered amps are more dangerous to speakers than over-powered amps.
This amp is rated at ~30 watts at a certain acceptable maximum distortion. Pushed past that limit the distortion curve rises nearly vertically and square waves might come out of it. Likewise, the speaker's 50-watt rating assumes acceptable distortion limits. Feed it a 50-watt square wave and smell the smoke.