Roland G wont power up.

[Carlosraj]

Hi

This Roland G is completely dead. I checked the 9V DC adapter and it is OK. Upon checking the power supply board, there is a 5V normal regulator and a smd 3.3V regulator. Both are OK. I have checked the smd resistors,, diodes and transisitors, and they test OK. I have also checked the + and - voltages on all the 8pin smd ICs and the voltages are there.There is also a 8 pin IC - NJM2360A, a DC-DC controller IC. I do not know whether this IC is OK or not. I do not know how to test it and what is the function of this IC. Please assist.

Rgds

Carlos

[nickb]

Without a schematic it's hard to say as the chip can be used in different ways, but in general, I'd expect to see a switching waveform on one of pin 1 or 2.

A search for "Roland G" comes up with nothing. Are we missing some numbers?

[Carlosraj]

HI

Attached is the schematic. The power supply is on page 33.

Tks

Carlos

[Carlosraj]

Hi

Attached is the schematic. The power supply is on page 33.

Tks

Carlos 512718457-Juno-G-j-Service-Notes.pdf

[nickb]

It's wired as an inverting boost converter. I'd expect about -9.7V on C55 based on the expected drop across Q12 of 0.7V. You can also check C52 for -9V.

With nothing on the display, you should check power and connections to the display. Also check the processor for power, clocks and reset.