I have a capacitor attached to one of the legs of the dash voltage regulator. Something to check

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Is the 5v dash/gauge regulator actually on when you're in the ACC position with the key?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

no

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50 chrysler,54 Plymouth, 64 Valiant conv 4 speed, 66 Valiant V8 wagon, 70 Challenger R/T 440+6 conv 4 speed,80 Colt, 98 Neon ACR,84 Honda V45 Magna
Taking care of 57 300C conv,48 T&C conv. Missing my 67 GTX and 36 Ply coupe

I have owned two 60's rigs that did not "hash", instead, the regulator was very slow and clicked on and off about the speed of a turn signal click. The gauges all moved sort of jerky, due to that.

I've also owned other rigs that had the "hash" noise. It was easy to determine, all you had to do was smack the dash with the radio on and the "hash" noise would respond by changing, and it was easy to ascertain "cause and effect".