Amp had a damaged rca jack.Replaced the jack and tested the amp.
Without a load across speaker terminals the output is fine as you'll see in the pic.
With a 2 ohm load connected at speaker terminals it starts distorting as the pic will show.
I can't figure out what the problem is.Things I do know...
- speaker has 1k resistor in series with the secondary center tap
There's .7 vdc measured from rca shield to - speaker terminal
Only the output rca shield is directly connected to sec center tap
There is practically 0 VDC offset across speaker terminals
Amp works okay otherwise
I found a past thread with identical problem but no responses with a solution.If there is one.
Without a load across speaker terminals the output is fine as you'll see in the pic.
With a 2 ohm load connected at speaker terminals it starts distorting as the pic will show.
I can't figure out what the problem is.Things I do know...
- speaker has 1k resistor in series with the secondary center tap
There's .7 vdc measured from rca shield to - speaker terminal
Only the output rca shield is directly connected to sec center tap
There is practically 0 VDC offset across speaker terminals
Amp works okay otherwise
I found a past thread with identical problem but no responses with a solution.If there is one.
Well,as soon as let's me post the other pictures I'll do so.Apparently I can't upload more than one pic at a time??..
Looking at the signal on pin 3 of the LM361, how does the signal change with and without the speaker load?
I'm not sure what the deal is but I think it's okay.I retested it and kept changing the scope ground location.Im guessing I didn't notice this earlier or maybe didn't do it.Was ground the scope to the - speaker terminal.
With the scope grounded to sec center tap the waveforms are as posted.When scope is grounded to - speaker terminal the waveforms are okay.I don't understand why and how I didn't catch that sooner but I suppose it's okay.
Perhaps it having a 1k resistor from secondary center tap to - speaker terminals has something to do with it.
With the scope grounded to sec center tap the waveforms are as posted.When scope is grounded to - speaker terminal the waveforms are okay.I don't understand why and how I didn't catch that sooner but I suppose it's okay.
Perhaps it having a 1k resistor from secondary center tap to - speaker terminals has something to do with it.
OK.
As a side note, the signal going into the 361 won't always look like audio. It is whatever signal is required to make the output of the amplifiers a clean, distortion free signal. The reason that it's clean at pin 4 with no load is because it's extremely easy to produce a clean signal with no load. As the load increases, the drive signal required to produce a clean output changes and the amplitude will increase, looking nothing like the signal being fed into the amp or the output to the speakers.
As a side note, the signal going into the 361 won't always look like audio. It is whatever signal is required to make the output of the amplifiers a clean, distortion free signal. The reason that it's clean at pin 4 with no load is because it's extremely easy to produce a clean signal with no load. As the load increases, the drive signal required to produce a clean output changes and the amplitude will increase, looking nothing like the signal being fed into the amp or the output to the speakers.
At first I wasn't then I did after I seen the original waveforms.During all of that I can't believe I never grounded the scope on the - speaker terminal.
With the scope grounded to speaker(-) even with ungrounded(cell phone) signal source.The signal is clean.Equally clips above/below ground.
I'm going to do more testing tomorrow to see if the clean signal was a fluke.
Also,the signal on pin 3 didn't seem to clip evenly above/below ground and the trace was fairly thick.I kind of gave up investigating the 361 when I had a clean output signal.
With the scope grounded to speaker(-) even with ungrounded(cell phone) signal source.The signal is clean.Equally clips above/below ground.
I'm going to do more testing tomorrow to see if the clean signal was a fluke.
Also,the signal on pin 3 didn't seem to clip evenly above/below ground and the trace was fairly thick.I kind of gave up investigating the 361 when I had a clean output signal.
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