Fixing A 30-year Old Roland Bug

The Roland CM-500 is a electronic synthesizer seem module introduced in 1991 that brings together two incredibly highly effective engines into one particular device. On the other hand, in 2005 enthusiasts of the Roland MT-25 (a single of the engines that went into the CM-500) discovered a distinction in between the vibrato level on the MT-25 and the CM-500, rendering it less valuable as now midi information would will need to be altered in advance of they sounded right. Now thirty-something a long time later on, there is a take care of as a result of the efforts of [Sergey Mikayev] and a wonderful writeup by [Cloudschatze].

They attained out to Roland Japan, who made the decision that due to the fact the device’s lifecycle experienced finished, no investigation was warranted. That led the group to start out comparing the differences amongst the two devices. Just one visible variance was the improve from an Intel 8098 to an 80C198. In concept, the latter is a superset of the previous, but there are a couple dissimilarities. First, the crystal frequency is divided by three instead than two, which suggests the interval of the LFO would transform even if the crystal stayed the exact same. Switching the 12 MHz crystal out for 8 MHz gave the LFO the right interval, but it broke the timings on the MIDI relationship. Even so, this is just placing the serial baud amount divisor, which involves modifying a couple of bytes.

Swap the ROM chip with a socket so you can slot your recently flashed PDIP-28 64kx8 ROM into a brief desoldering. Then swap the crystal, and you’ll have a machine that matches the MT-25 properly. The discussion board post has comparison audio documents for your pleasure. Lastly, if you are curious about other fixes demanding an inspiring amount of effort and hard work and determination, here’s a match installer that was brought back again from the dead by a decided hacker.