Working on a 500aII that outputs 26Vrms on one channel and 22Vrms on the other. I have no load on the outputs and feeding a 1Khz sine to the inputs.
The rail voltages read +-49Vdc. When I got this amp one channel was completely blown, all fets were shorted. I have since got that channel operational, that one outputs the 26Vrms. Even loading the outputs with 3ohm load makes no difference.
It seems to me the output waveform should be closer to 30Vrms. Could sourcing from an mp3 player be causing some issue. I know Perry has mentioned that in the past.
Any thoughts
Cory
The rail voltages read +-49Vdc. When I got this amp one channel was completely blown, all fets were shorted. I have since got that channel operational, that one outputs the 26Vrms. Even loading the outputs with 3ohm load makes no difference.
It seems to me the output waveform should be closer to 30Vrms. Could sourcing from an mp3 player be causing some issue. I know Perry has mentioned that in the past.
Any thoughts
Cory
I don't know if Rockford amps are sensitive to floating grounds. If the mp3 player is operating on battery power, you can connect a jumper from the shield ground to the chassis ground to eliminate the floating ground.
Does the amp clip at 22 and 26v?
If not, are the gains at the max position?
Does the amp clip at 22 and 26v?
If not, are the gains at the max position?
Scope reads 270mVrms, meter confirms. I've never had issue before with this setup. MP3 player won't be used anymore, see below!!
Swapped out the mp3 player, pulled the cd changer from the attic and will be using it from now on. I get roughly
2.2Vrms on the input now, the outputs can be driven to clip. They both clip around 35Vrms. Should I worry about the input difference with low amplitude?
Cory
Swapped out the mp3 player, pulled the cd changer from the attic and will be using it from now on. I get roughly
2.2Vrms on the input now, the outputs can be driven to clip. They both clip around 35Vrms. Should I worry about the input difference with low amplitude?
Cory
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Measure the AC voltage at each non-inverting input for each op-amp in each channel and for each op-amp output in each channel. Compare the left channel to the right channel to find the point where the signal drops off. If I'm not mistaken, all non-inverting inputs should equal the outputs for each op-amp section except for the first op-amp (U101) in the circuit which will likely lose ~10% and U104/204 which will vary depending on the gain setting.
Yes, non-inverting input and output at all stages of the input. I follow it until C111 or C223.
With no load and gain adjusted to just before clipping on the output it will produce 35Vrms, loaded at 3 ohms is roughly 28.5Vrms. The voltage reading is from the scope measuring function, pk to pk is of course higher.
Seems odd, I will swap my right and left channel from the mp3 player and see if it follows it.
Cory
With no load and gain adjusted to just before clipping on the output it will produce 35Vrms, loaded at 3 ohms is roughly 28.5Vrms. The voltage reading is from the scope measuring function, pk to pk is of course higher.
Seems odd, I will swap my right and left channel from the mp3 player and see if it follows it.
Cory
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