Thanks Yamaha fans
The warmer weather has come and I have succeeded in opening up the Yamaha Organ EL40 that had several notes on upper and lower keyboards that sounded full blast when using any percussion sounds.

I didn't have to buy any parts and reused the same rubber pad strips
I exposed the internal note circuits and cleaned with a contact cleaner sprayed on a cotton bud, followed by a quick rub with a very very fine abrasive paper---- I also swapped a couple of keys that were finger nail damaged and reput them at the lower end of the keyboard where they don't get much use.
You don't have to remove the Disk drive to get the keyboards out
The many screws to remove were either self threading or fine threaded so you need to remember as you have to take out several dozen screws.

Hope this helps other handy people that must have had a similar problem with a Yamaha Organ.

Dave L.