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Roland Cube distortion

N

N Cook

Jan 1, 1970
0
On "octave bass" setting only , which of course is the one used.
A sort of auto-wah effect at the flanger rate but with the effects controls
turned to off position. Alternate peaks of a 200 Hz input signal are
attenuated.
Thats with the gain pot at about 60 percent but above 70 percent then a
cross-over type distortion moves into the attenuated traces as well.
No response to twizzle stick or ribbon connector movement,SM IC pushing etc.
Not fully taken apart yet , but any ideas ?
 
N

N Cook

Jan 1, 1970
0
N Cook said:
On "octave bass" setting only , which of course is the one used.
A sort of auto-wah effect at the flanger rate but with the effects controls
turned to off position. Alternate peaks of a 200 Hz input signal are
attenuated.
Thats with the gain pot at about 60 percent but above 70 percent then a
cross-over type distortion moves into the attenuated traces as well.
No response to twizzle stick or ribbon connector movement,SM IC pushing etc.
Not fully taken apart yet , but any ideas ?

Should have said Roland Cube 30. Looks now more like a no goer.
Any known problems with the system of pots (nothing ohmically wrong) turning
to 0 ohm to switch off digital effects?, the LED goes out but it is as
though the micro doesn't know that.
Good sine signals through both sides of dual opamps IC1 and IC2, distorted
signal at both sides of same IC , IC3.
+/-8V supplies to the opamps good and clean as is 3.3V rail for the
following.
Tracing signal back it seems to go to IC4 an AKM4552VT no data found but
AKM4550VT is an Asahi ADC/DAC of same 0.65mm format 16 pin but slightly
different pinning.
Good sine in but distorted signal out so presumably the digital processing
is buggered somehow.
I doubt if a schematic would help if its a corrupt micro.
 
N

N Cook

Jan 1, 1970
0
N Cook said:
Should have said Roland Cube 30. Looks now more like a no goer.
Any known problems with the system of pots (nothing ohmically wrong) turning
to 0 ohm to switch off digital effects?, the LED goes out but it is as
though the micro doesn't know that.
Good sine signals through both sides of dual opamps IC1 and IC2, distorted
signal at both sides of same IC , IC3.
+/-8V supplies to the opamps good and clean as is 3.3V rail for the
following.
Tracing signal back it seems to go to IC4 an AKM4552VT no data found but
AKM4550VT is an Asahi ADC/DAC of same 0.65mm format 16 pin but slightly
different pinning.
Good sine in but distorted signal out so presumably the digital processing
is buggered somehow.
I doubt if a schematic would help if its a corrupt micro.

Looks like a pot problem
Tracing the lines back to the 48 pin IC8 Roland chip then pin 22 goes to the
LED and the wiper of the effects pot goes to pin 4 via 100R.I don't
understand why with a few ohms left on the pot at "zero" the LED goes out
but the effect does not stop. Rather than trying to change the sub miniature
pot I'll add in a switch to ground on the pin4 side of the 100R, as the
owner never uses the effects anyway.

The crossover problem was not realising I was on the wrong sig gen
attenuator setting.
 
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