On 2014-Sep-03, at 9:33 AM, Chuck Guzis wrote:
On 09/03/2014 08:14 AM, drlegendre . wrote:
Came across something else last night.. are the
power transformers (in B
model PSUs) known to be a bit on the leaky side?
Does the PSU use capacitors to bypass RFI from the transformer to the chassis? If so,
there's probably your answer. Properly, those should be Y-rated safety caps.
But note it doesn't necessarily mean the capacitors are bad or leaky. If the ground
lead is open, the common arrangement of line-filter caps (the two caps from line and
neutral to gnd) produces an AC voltage divider which will leave the chassis at 1/2*mains
VAC, e.g. 60 VAC in North America.
Any piece of equipment with the common line filter and a 3-lead (grounded) power cord
*needs* the ground connection.
Such caps have a high enough impedance at 60Hz that current is limited, but with the
ground lead open it's certainly enough to produce noise problems and perhaps a tingle
when touched.