ROLAND SA-300 Portable PA noise

[acaselli]

Hi, I'm Andrea from Italy, this is the first time I write here.
I have a 2pc Roland SA-300 PA, and one of them have a strange noise, similar to a variable frequency modulation (seems old radio signal in the space..).
The noise level follow the VOLUME knob, and it it related to the MAIN board (it have a microprocessor, a RAM and another chip... I have to identify) and all audio chips with related tens and tens CAPs.
If I push the board or I move some shielded cable, the noise change the frequency.


Somebody have experience on this model, can help me to finde the cause? How to identify bad CAP, cables other?
I cannot find the schematics, sombody have?

Thanks so much,
Andrea

[sugeda]

..

[acaselli]

Thanks so much for the schematik, sugeda!!!
I will try to study the signals paths.

Grazie,
Andrea

[acaselli]

Hi guys, SOLVED !!!!




A strong re-CAP on the Main Board.
Some CAP near the 4 ADA and the 5 others on the power supply.
Thanks again for this forum, and I hope my post can help others.