I'm intending to use 2 or more boards connected to my A90 by a flat cable.
Although it seems I can use only one at a time, I may use an external switch to cut off the positive and negative to the boards not used and turning on the keyboard, it'll initialize the board I want. (I'm not sure if it's possible to use VE-RD1 as part 1 to 4 and VE-JV1 on other parts at the same time)

This will make the ability to change boards without openning the board house with screw driver, saving a lot of time and not putting on risk the boards with handling.

Does anyone ever tried it?
I would like to know if the boards have tri-state output with high impedance in order to see if it's possible to parallel all the connector pins or it's necessary to cut all the 20 pins of the connector.

Does anyone have the schematic diagram for the connector of the A90?
It's the same as A70, JV35, JV50, JV90 and JV1000.

Thanks.

I thought of building a switcher for the JV-1010, but bought a JV-2080
instead.

Pins 19 & 20 are vcc. 9, 10 are ground. I assume you would need to switch
all wires.
The pinout is as follows:
AN0,1,2,3,4,5, Sense, xrst, Dgnd,Dgnd, DACA,DACB,DACC,Sdata,
sck,clk,Rxd,Txd,vcc, vcc

Part # of A70 connector is j3439157 (for second board)

Thanks, Robert.

Is it the pinout for VE boards to A90/A70 connector or JV/XP boards for JV1010? They are not the same.

A70 boards pinout.
I believe SR-JV80 cards are 40 pins. I have that layout also.

Thanks again.
There are still some doubts. I'll be very grateful if you can help me again.

Do you have some literature, or site in the net, about the working principle of these boards?

AN0 to AN5 stands for Memory Address Number? or something Analog ?

I don't know the purpose of the Sense pin also.

Xrst may be external reset, Dgnd Digital ground and Vcc voltage supply.

DACA to DACC may be digital to anolog converter A,B and C. But why 3 of them?
Is the amplifier and audio circuits in A70 or inside the board?

Is Sdata and Sclk a secondary serial port?
What kind of data is transmited on it?

Is Clk,Rxd and Txd another serial port? Is it used to receive MIDI info or a proprietary Roland protocol?

Regards,
Fernando

Not much info in the service manual.
Yes ,of course on vcc & ground.

AN 2 & 3 appear to be only ones active. DACC likewise only one active.

Audio is spread across main board and left board, not in accessory card itself.

Sense "VESense" and xrst are tied to "control bus"
Rxd & txd are tied to Midi bus.

So, switch pins 3,4,7,8,9,10,13-20 & see what happens.