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Hello, I am reaching out for help for a Roland DM-2100 speaker system.
This is an active speaker system and the speaker with the active electronics fell down on the potmeters.
I have been troubleshooting this one for quite a while now and I need help.
Apart from the tone control everything works great (including the bass).
So far I have replaced the bass level pot and the bass came back alive after replacing it. I am having serious difficulty troubleshooting the tone control however.
This thing is working with NJM4558L SIL opamps. The opamp that controls the tone control pot has output on both pins 1 and 7. However the tone control pot does not do anything.
I have a working example here too and when turning the tone pot you can clearly hear the high pass and low pass filter coming in and out. On my not working unit sadly not.
Voltages on opamps are 11,98V and -12,15V
Could it be that the NJM4558L SIL is bad and still give output signal?
Because I don't have a dual gang pot, I currently replaced it with wires leading to 2x 20kA alps pots. Still no tone control. All traces check out and conduct, no lifted pads. The original dual gang pot was a linear type but I am having difficulty finding that exact model. I am guessing that the log pots don't form a problem for testing purposes.
This is the situation:
https://imgur.com/a/n4CuJpl
I do not have a schematic of these monitors.
This is an active speaker system and the speaker with the active electronics fell down on the potmeters.
I have been troubleshooting this one for quite a while now and I need help.
Apart from the tone control everything works great (including the bass).
So far I have replaced the bass level pot and the bass came back alive after replacing it. I am having serious difficulty troubleshooting the tone control however.
This thing is working with NJM4558L SIL opamps. The opamp that controls the tone control pot has output on both pins 1 and 7. However the tone control pot does not do anything.
I have a working example here too and when turning the tone pot you can clearly hear the high pass and low pass filter coming in and out. On my not working unit sadly not.
Voltages on opamps are 11,98V and -12,15V
Could it be that the NJM4558L SIL is bad and still give output signal?
Because I don't have a dual gang pot, I currently replaced it with wires leading to 2x 20kA alps pots. Still no tone control. All traces check out and conduct, no lifted pads. The original dual gang pot was a linear type but I am having difficulty finding that exact model. I am guessing that the log pots don't form a problem for testing purposes.
This is the situation:
https://imgur.com/a/n4CuJpl
I do not have a schematic of these monitors.
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