I and some other techs have noticed that D5 cleaned contacts develop a greenish 'growth" over time
Rob's on the money with that observation.
Here's my advice for servicing good quality patchbays (Switchcraft, ADC, Neutric etc).
1. I never spray anything wet inside a patchbay, even if it's an evaporative spray.
Firstly the compressed air propellent will disturb any dust residing in the patchbay and that dust will then cling to the wet surfaces before the spray has time to evaporate.
If the spray contains any oil then that oil will stay there the and any dust in the future will bind to it. Over a period of time that oil/dust combination can bridge contacts and cause you grief.
Note: The normalling contacts on patchbays are designed with a self wiping action, as the contacts make or break, the wiping action cleans the contacts.2. The only thing you really need to clean on a patchbay is the tip, ring and sleeve of the jack.
The way to do this is with a Burnishing Tool and only when there's a problem. This is tool looks exactly like patchbay plug except it's all metal.
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You simply insert the burnishing tool and rotate it a couple of times and you're done.
Use it sparingly, as they are slightly abrasiveIf patch bays are in a clean enviroment and are used regularly, the action of inserting a regular patch bay plug and removing it is all that is normally required to clean it.
Use a bit of preventitive maintenance, make sure patch plugs are kept clean, and once a month insert and remove a patch cord 2 or 3 times into each jack on the bay.
Lastly if you are going to vacuum the patch bay, if possible, vacuum from the rear of the bay.
Hope this helps.