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This PA power amp has burned out the 'hot' output tracks on the little piggyback PCBs attached to the Speakon sockets after being "driven hard and red hot" before it finally died. No other damage and PCBs now repaired, but a voltage check shows 81v-0-81v on the main supply rails. The DC test points on the PSU board are labelled 58v-0-58v
The transformer is 56v-0-56v, feeding a simple bridge and filter cap arrangement. The actual AC is 59v, so the 81v output is right for the configuration. The filter caps are 80WV. The amp will push 625w per channel at clipping into 4 ohms with a strong input. It's rated at 400w per channel, so little wonder the tracks are toast. It sits there nicely at its rated output, though, and I'm happy with the output waveforms.
Does anyone know if the voltages are correct for this amp? There's a series of these Chinese-made amps with different output power ratings and I wonder if the PSU board comes from another amp down the line (hence the lower voltage markings). The transformer looks like an original component (possibly doing service in higher-output amps) so could be that they've used a modular approach in assembling it?
The transformer is 56v-0-56v, feeding a simple bridge and filter cap arrangement. The actual AC is 59v, so the 81v output is right for the configuration. The filter caps are 80WV. The amp will push 625w per channel at clipping into 4 ohms with a strong input. It's rated at 400w per channel, so little wonder the tracks are toast. It sits there nicely at its rated output, though, and I'm happy with the output waveforms.
Does anyone know if the voltages are correct for this amp? There's a series of these Chinese-made amps with different output power ratings and I wonder if the PSU board comes from another amp down the line (hence the lower voltage markings). The transformer looks like an original component (possibly doing service in higher-output amps) so could be that they've used a modular approach in assembling it?