Page 1 of 1

Roland MC4 Memory?

PostPosted: Sun Oct 19, 2014 11:37 am
by harry
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!

Re: Roland MC4 Memory?

PostPosted: Sun Oct 19, 2014 8:50 pm
by Thirteen
If you get stuck I may have some RAM at my workshop, send me a photo of the top of the IC and I will see if I have any that matches.

Re: Roland MC4 Memory?

PostPosted: Sun Oct 19, 2014 8:51 pm
by Thirteen
I also have a couple of brand new MC-4 keypads somewhere from memory.

Re: Roland MC4 Memory?

PostPosted: Sun Oct 19, 2014 8:59 pm
by harry
Thanks Steve!

I'll send you an email.


Re: Roland MC4 Memory?

PostPosted: Sat Nov 22, 2014 5:00 pm
by harry

NOS memory from ebay fixed the issue - now this MC4 holds the same amount of memory as the other known working machine.

Thanks everybody!