The foil is already either acting like an antenna or creating a ground
loop. Since the “real” ground is connected, it is probably a ground loop, so
eliminating that one ground could cause a significant difference. Either way, it
can provide some clue to what is going on if it makes a difference.
Sent: Saturday, September 5, 2015 1:02 PM
Subject: Re: [PolySix] Re: Noisy Polysix
Leaving the foil floating would turn it into a big antenna - radiating/coupling noise throughout the area, to every board... you have to review every wired ground connection and make sure they're typically made back to a common point at the power supply (star topology) so they don't pick up each others noisy currents.
There is that 'june production fix' I've seen on Old Crows's...
As far as keeping that midi interface:
a) it's messy, and a hazard to deal with
b) it's power hungry and loading the
supply meant only to power the original circuitry - could lead easily to
premature failure due to additional load/heating stress (something the folks at
KIWI mention as a reason to replace with their modern upgrade - though
incredibly expensive!)
c) it covers up and blocks access
to way too much circuitry...
d) a new assembly from CHD would keep
thing compact and minimize any related headaches of wires / grounds and all the
rest
e) A new interface would increase the
value of your synth - no if's, ands or buts.....
No doubt there's still work to be done
to get rid of those 'gremlin' noises...again, you seriously have to clean things
up first before you can deal with that in a reasonably effective manner... just
common sense really.
That jumpering was poorly done... also
if there's even the slightest
bit of battery residue on the board (in the wrong place), it's highly conductive and will connect
signals that should otherwise be isolated - the exact symptom I dealt with to
fix a fellow's P6.
You can't clean what you can't get at,
buried under a mass of poorly installed jumper wires or being blocked by an
oversized, oldschool sized interface from the previous century....
These points are rather straight forward, but if you have any doubts about
doing it properly, hire a tech or even
an assembler... well worth the investment and again increases the
serious value of the synth for when you decide to part ways.
Otherwise, poking around forever and a day, however 'entertainingly
productive' it may seem and you might still get lucky and find the issue,
otherwise just drags out the inevitable....