Fixing A 30-year Old Roland Bug

Fixing A 30-year Old Roland Bug

The Roland CM-500 is a electronic synthesizer sound module launched in 1991 that combines two very impressive engines into one unit. Nonetheless, in 2005 lovers of the Roland MT-25 (a person of the engines that went into the CM-500) noticed a difference amongst the vibrato fee on the MT-25 and the CM-500, rendering it significantly less beneficial as now midi information would want to be adjusted in advance of they sounded right. Now thirty-some thing decades later on, there is a repair by the endeavours of [Sergey Mikayev] and a fantastic writeup by [Cloudschatze].

They arrived at out to Roland Japan, who made a decision that considering the fact that the device’s lifecycle had ended, no investigation was warranted. That led the neighborhood to get started comparing the dissimilarities involving the two systems. Just one noticeable distinction was the change from an Intel 8098 to an 80C198. In idea, the latter is a superset of the previous, but there are a handful of distinctions. First, the crystal frequency is divided by 3 instead than two, which implies the period of the LFO would improve even if the crystal stayed the exact same. Altering the 12 MHz crystal out for 8 MHz gave the LFO the proper interval, but it broke the timings on the MIDI connection. On the other hand, this is just setting the serial baud rate divisor, which calls for altering a few bytes.

Substitute the ROM chip with a socket so you can slot your recently flashed PDIP-28 64kx8 ROM into a swift desoldering. Then swap the crystal, and you’ll have a device that matches the MT-25 flawlessly. The forum write-up has comparison audio data files for your satisfaction. At last, if you are curious about other fixes necessitating an inspiring sum of effort and devotion, here’s a game installer that was introduced back again from the useless by a decided hacker.

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