I have a Roland E-35 keyboard that is working great, however after playing music, when sounds are stopping, then there's noise/hum for couple of seconds. Problem is very obvious on internal speakers. On "headphone output" is less significant and I can't hear it on "line output".
I couldn't find "E-35 service notes" in the Internet but E-35 have similar "CPU Board" and "GSE Board" like in E-70 model and "Power Supply & Amplifier Board" is like in E-15 model.
I think capacitor/capacitors are guilty but optically all capacitors on boards looks ok. Can you help me localize source of problem? Then I can unsolder some elements and check them in LCR tester.
I've attached example audio file which is amplified and you can hear that after 3 second hum is gone and only noise floor is present.
I assume you have ruled out the external power adaptor as the culprit?
Yes. Checked on two different power adapters.
Here are additional infos and some pictures with schematic diagrams and photos of the instrument boards.
The instrument has weird volume control circuit - the slider adjusts the sound level right after the DAC system, before the input to the power amplifiers. This would suggest that the problem is somewhere on the Power Supply & Amplifier Board.
Interestingly, even when the volume slider is set to minimum where the sounds generated by the instrument cannot be heard, the hum I described can be heard. Also, when the volume slider is at minimum and you start playing on the instrument then various noises can be heard on the speakers.
I cannot localize the source of the problem the only solution in my mind is to replace all electrolytic capacitors. But is it possible that other components apart from capacitors have died and can cause the problem? Can you advise me what kind/producer of caps should I buy with long life?
Its over 30 years old, caps are generally great for 15 years and really go downhill after 20 depending on the quality.
Go with Nichicon and Chemi-Con and its good for another 30 years, and there are so few caps the order is going be
$30 including shipping from Digikey or Mouser.
I always replace capacitors on most music gear older than 2003.
*Check you have the correct DC voltages from the power supply.
-William
According the to data I have, the E15 requires 9v 1A, the E35 requires 12v 1.6A.
This still may be just a power supply issue.