The opportunity to use a thermal imaging camera when refurbishing a Roland MKS70 yielded some interesting results. These measurements are equally applicable to the Roland JX10, although that instrument is likely to run cooler due to the fact that the boards and assemblies are separated out and in a larger volume case.

Measurements

Overview

Here is a view of the interior after being on for two hours with lid off, in an ambient temperature of around 24 degrees. It shows a maximum temperature rise of 29 to 30 degrees C.

Power Supply

Picture below shows a close up of the Power supply. The transformer looks to be the hottest item, however the heat sink on the MKS70 is under the voice boards on the metal base. Transistor temperature was about same as transformer with the transistors for the +/-15V power supplies being 2 degrees lower.

The main issue with the power supply is not the temperature rise, but the volume that is generated from a 1Kg transformer and a huge heat sink under Voice Board A that dissipates heat into the bottom of the enclosure.

Voice Board Processor – PWM Upgrade

The processor section of the voice board reveals that the NMOS 8155 interface chip IC14 is a hot item. This chip is mostly used to provide output ports used for driving the multiplexers.

Note that this is a fully upgraded instrument, the processor and ROM are modern CMOS low power devices and so do not get hot. A PWM upgrade kit with CMOS ROM devices does reduce the current consumption and internal heating. Especially with recent updates shown on this page.

The picture below shows a Voice Board upgraded with the Vecoven PWM. The modern CMOS processor and ROM are cold.

Voice Board Processor – Stock

Conversely the picture below shows a Factory stock SuperJX voice board. The NMOS processor and ROM are very warm, arguably the hottest part of the instrument, 32 degree rise. The ROM was measured at 45 degrees C.

Voice Board Analogue

The analogue section of the voice board reveals a delightfully cool set of integrated circuits, the filter chips being only slightly warm, demonstrating a great design. The hottest part with only an 18 degree C rise, being the output amplifiers that drive the audio signal.

Front panel – Upgraded VFD

The SuperSynthProjects VFD shows a 20 degree temperature rise reflected to the display board. This is expected and considering the power consumption of the VFD is 3 watts, shows a good distribution of heat that is stress free.

The VFD was tested separately during the design to optimise heat dissipation and component choices.

Conclusion

The Roland design is well thought out and the original engineers gave thermal and power characteristics a great deal of consideration.

Vintage instruments literally “cook” and although upgrades tend to reduce the overall power dissipation, it needs consideration when installing in a rack with other equipment.

The commercial temperature rating of the integrated circuits employed in the design are often only up to 70 degrees C. An ambient temperature that increases another 10 degrees due to hot climate plus any rise from adjacent racked units will certainly push some components close to that rating thus shortening their life or affecting sound quality.

Other vintage equipment fitted adjacent to the MKS70, for example another MKS70 or MKS80, can increases the ambient temperature in the rack significantly. Other issues that cause problems are where rack enclosures are used that don’t have proper ventilation and made of wood, thus not allowing the heat to dissipate.

When installing next to other vintage or heat generating equipment, it is recommended using ventilation rack spacers. They are available in sizes 1/3U, 1/2U, 1U & up.

Special Thanks

Special thanks to Keith Meiere of Super JX Zone for providing the thermal camera, see his fabulous resources for many synths here on his  Super-JX Website.

 

Copyright © 2020 Super Synth Projects, Guy Wilkinson. Llama Music, Keith Meiere.