I’m seeing an issue with a newly purchased Roland JV-880 that I cannot find any information about.
I installed a Roland ROM card (in the front “data card” slot) that corresponds with a working expansion board installed in the unit. The ROM card should show up as bank C, but it doesn’t.
I found the service manual and ran a RAM test on the unit, and when I push the card in, the test result is “battery LOW”. The description of the error in the service manual is:
“The voltage of the battery in the memory card is low, or the voltage measuring circuit (IC14) or associated circuit is defective”.
There is no battery in the card, since it is a ROM card, so I believe the problem is with the voltage detection circuit.
For context, IC14 is a simple opamp configured as a buffer. This feeds the voltage coming from the data card battery (or thru voltage of VCC through the ROM card, I think) to input AN0, which is an ADC input on the processor.
I opened the lid and started looking at voltages.
- VCC from the 5VDC power regulator IC measures 4.91V
- The voltage coming from the data card “battery line” (VBB) is 4.88V
- The VBB voltage passes through a resistor and drops voltage to 4.26V (this is the voltage on the non-inverting input of the op-amp).
- The voltage coming out of the op-amp heading to AN0 is 4.36. This is curious, since the op-amp is configured for unity gain.
My questions at this point are:
- Is the 5V VCC out of spec? It doesn’t say in the service manual what the expected voltages are.
- What is the “low battery” threshold for a Roland RAM/ROM card?
- Is there a way of testing the data card itself to see if the card is the problem? (I don’t have another card at the moment)