Winter Maintenance 2018/19 - Removal of the Equipment Case and Electronics

[TerryJC]

A week or two ago, I removed the equipment case and Quarter Jack from the Minster with a view to having another go at solving the niggling things that have occurred since the original installation lat year. Some changes were made last April, but although many of the problems have been reduced, they were not solved.

The current plan is to:

1. Include two 12 V, 1 A linear regulators to provide a much cleaner power supply. Each Audio Amplifier will therefore have it's own (largely isolated) PSU.
2. Include a 12 V, 3 A Buck converter to provide an isolated power supply for the solenoids and the fan. This is an adjustable type (identical to the one's used in the Sump and Butts Pis, so I will be able to reduce the power to both the fan and the solenoids to provide the optimum compromise between performance and noise.
3. Look again at the temporary measure that I included during the summer to switch off the mains power to the system overnight. If the above measures work, then this may not be needed.
4. Look into providing better ventilation and an airflow in the Nave, to refuce the summer temperatures in there.

If these measures do not provide a sufficiently acceptable solution, then I will look into repackaging the system in an alternative case; perhaps using a similar approach to the one used for the Railway Lighting.

[TerryJC]

The system has now been working normally since it was re-installed just before opening for the summer season. In the end, I didn't use new linear regulators and or include a buck converter.

Instead I discovered that by re-instating the earthing scheme that had originally been designed, the hum pretty much disappeared. I'm uncertain as to why that scheme didn't work originally, but it may be due to the addition of the PSU input filter and AF isolating transformers; without these the earthing had no effect, with them it worked.

I updated the software to ensure that the music came on when the system started after a night shutdown; the new version has been uploaded to gitLab.