Roland MC4 Memory?
Posted: Sun Oct 19, 2014 11:37 am
Hello all,
I'm restoring an MC4-B at the moment.
It works okay, however there seems to be far less memory available than another MC4-B that i am comparing it to.
A scan of the service docs reveals that the machine uses 1bit 16k ram - M5K4116 (mitsubishi ram). It groups the chips in sets of 8 to form 8 bit 16k memory.
In total there 8 x M5K4116 on the main board, and a further 16 x M5K4116 on the Ram Board for 48k total.
Would i be right in assuming that the OS uses some kind of a 'checksum' to map out the available ram? If so does it limit memory capacity to wherever an error is present on an address of the chip?
- I have roughly 9% memory capacity compared to that of a fully working MC4B (verified by loading an identical sequence into both machines and using the 'available memory' command to check how much memory is available.
- Disconnecting the Ram Board does not change this - therefore i have a problem on the main board ram.
- Placing the ram board from the faulty machine into the new machine shows that it works, however there is slightly less memory available (so this board also has an issue)
I was going to start by desoldering the 8 ram chips on the cpu board (i have good desoldering equipment), socketing, and then putting in new ram chips. Is there a way to test if a particular ram block is working? and should i be looking at replacing the related ram address chips as well?
The M5K4116 ram seems to be a derivative of generic 4116 ram - should i go for the original stuff, or would any generic 4116 ram do? - I have the feeling that different manufacturers ram might have different timings etc that might be an issue - the mitsubishi stuff is more expensive and harder to find...
Thanks for your time!
I'm restoring an MC4-B at the moment.
It works okay, however there seems to be far less memory available than another MC4-B that i am comparing it to.
A scan of the service docs reveals that the machine uses 1bit 16k ram - M5K4116 (mitsubishi ram). It groups the chips in sets of 8 to form 8 bit 16k memory.
In total there 8 x M5K4116 on the main board, and a further 16 x M5K4116 on the Ram Board for 48k total.
Would i be right in assuming that the OS uses some kind of a 'checksum' to map out the available ram? If so does it limit memory capacity to wherever an error is present on an address of the chip?
- I have roughly 9% memory capacity compared to that of a fully working MC4B (verified by loading an identical sequence into both machines and using the 'available memory' command to check how much memory is available.
- Disconnecting the Ram Board does not change this - therefore i have a problem on the main board ram.
- Placing the ram board from the faulty machine into the new machine shows that it works, however there is slightly less memory available (so this board also has an issue)
I was going to start by desoldering the 8 ram chips on the cpu board (i have good desoldering equipment), socketing, and then putting in new ram chips. Is there a way to test if a particular ram block is working? and should i be looking at replacing the related ram address chips as well?
The M5K4116 ram seems to be a derivative of generic 4116 ram - should i go for the original stuff, or would any generic 4116 ram do? - I have the feeling that different manufacturers ram might have different timings etc that might be an issue - the mitsubishi stuff is more expensive and harder to find...
Thanks for your time!