A strong man who repaired Roland's synthesizer bug about 30 years ago by himself appears

If a bug is found in a product that was released several decades ago, most of the time the product cannot be repaired by the manufacturer and falls into disrepair. However, regarding the bug that existed in Roland's synthesizer released about 30 years ago, Mr. Cloudschatze, an enthusiast, has reported the result of repairing it himself.

Fixing the Roland CM-500 Vibrato Bug \ VOGONS
https://www.vogons.org/viewtopic.php?t=86257

The synthesizer that was reported to have been successfully repaired this time is the sound module 'CM-500' sold by Roland in the 1990s. About 30 years have passed since the 'CM-500' was released, but even at the time of writing the article, second-hand items are trading at around 30,000 yen, and it has gained a certain level of support from enthusiasts.

However, 'CM-500' has a bug that 'vibrato is faster than other products'. Click the link below and compare the sound output by 'CM-32L' (top) and the sound output by 'CM-500' (bottom). You can see that

・'CM-32L' vibrato
・'CM-500' vibrato

The above bug was discovered in 2005, and Roland also admitted that it was ``unintentional behavior''. However, when the bug was discovered, more than 10 years had already passed since the CM-500 was released, so it was not possible to receive official repairs from Roland.

After that, in 2020, an open source project `` Munt '' that emulates Roland synthesizers was launched, and a detailed analysis was also conducted on the `` CM-500 ''. As a result, the Intel processing chip '80C198' installed in the 'CM-500' has an operating clock that differs from that of the '8098' installed in products such as the 'CM-32L' before the appearance of the 'CM-500'. It turned out that the difference in vibrato speed is caused by the difference in the operating clock.

Based on the results of the project, a patch was created that would allow the CM-500 to operate in the same way as the CM-32L. Mr. Cloudschatze obtained a chip that can be installed in 'CM-500' and applied a patch, and succeeded in fixing the bug of 'CM-500'. Click the link below and compare the sound of 'CM-32L' (top) and the corrected 'CM-500' (bottom), and you can see that the vibrato speed is the same. .

・'CM-32L' vibrato
・Corrected “CM-500” vibrato

The correction work can be completed by simply replacing the two chips, but the chip is directly soldered to the 'CM-500', and it is difficult for people who have no soldering experience to do the work. For this reason, Cloudschatze advises getting help from someone in the know.