22-01-2022, 09:09 AM
"In this and previous threads, I have stressed the importance of measurements." We all have, we've advised Rob to measure the power supply voltages, to check the DC offset on OP of his amp and other bits and bobs. I admit to getting a bit grumpy with Rob sometimes as he doesn't seem to follow up on any suggestions we put to him. Spending five minutes going over your amp with your DMM will be invaluable Rob, more so than advice and suggestions from this end. A picture of an oscilloscope trace showing the OP of your amp and some voltage readings will mean a hell of a lot more than a description of the sound your setup makes. Lecture over here's some tips.
Get the amp on your bench or table or whatever, power it up and using your DMM on DC volts take readings on both speaker terminals, do the same for AC volts.
Next take the top off the amp, find the power supply PCB and take some DC readings of all the main rails, EG +/- 35v & +/- 15v DC etc. Now do the same with your meter on AC volts. Your looking for the big caps & smaller ones as well as any voltage regulator IC's, these are an indicator of where to check readings. Next check the manual or schematic and compare your readings to those hopefully on the schematic.
Connect an old speaker or better a dummy load to the speaker terminals, attach your scope probes, connect your signal generator to the input, set your sig gen to 1khz @ about 0.5v AC RMS turn on the amp and take pictures of the scope screen. While your at it take pictures of the inside of the amp, decent quality close ups of the PCB's and post here.
Write it all your results down and post here. Lastly Mark made a good point about speaker placement, see attached pics from a monitor manual I have for a rough idea.
Andy.
Get the amp on your bench or table or whatever, power it up and using your DMM on DC volts take readings on both speaker terminals, do the same for AC volts.
Next take the top off the amp, find the power supply PCB and take some DC readings of all the main rails, EG +/- 35v & +/- 15v DC etc. Now do the same with your meter on AC volts. Your looking for the big caps & smaller ones as well as any voltage regulator IC's, these are an indicator of where to check readings. Next check the manual or schematic and compare your readings to those hopefully on the schematic.
Connect an old speaker or better a dummy load to the speaker terminals, attach your scope probes, connect your signal generator to the input, set your sig gen to 1khz @ about 0.5v AC RMS turn on the amp and take pictures of the scope screen. While your at it take pictures of the inside of the amp, decent quality close ups of the PCB's and post here.
Write it all your results down and post here. Lastly Mark made a good point about speaker placement, see attached pics from a monitor manual I have for a rough idea.
Andy.
