The following is from Bruce Rogers, KQ6B, and is a follow-up to earlier CGC stories concerning severe RF  interference from Electric Blanket controllers, specifically those from Perfect Fit Industries. 

February 2, 2005

"...Two weeks ago Monday, I left a message on the customer service number of Perfect Fit Industries (all automated attendants).  It appeared that they were screening their calls. One week ago Monday I received a call-back from a human. Yesterday, I received a pair of replacement power supplies and controls.

The design of the new supply is significantly different from the original and it is easy to distinguish the new unit from the old. The new supply/control unit is shorter and smaller in size and doesn't have the vent holes. It has a molded RF choke in-line with the cord that is wired between the power supply and the temperature control.  On the original (interfering) unit, one cord went from the power supply to the blanket and one cord went from the power supply to the temperature control. On the new unit the power supply feeds the temperature control which then feeds the blanket.  There is no longer a visible light on the power unit either. The original unit had an orange (perhaps neon) backlight on the temperature control numbers. The new unit has a bright red (probably LED) backlight. The new unit also says FCC certified. In case you are interested for your newsletter or otherwise, I took close up pictures of the old unit and the new unit, including the certification label. 

When I plugged it in, I could hear a faint medium pitched hum -- perhaps a 300-600 Hz -- but I could no longer hear the faint clicking noise of the offending unit.  I am pleased that about 99.9% of the RF interference is gone.  The only interference that I found was when I put the unit immediately next to an FM broadcast receiver that was tuned onto a very weak station (I heard the 300-600 Hz hum). It is no longer getting in to my ham receiver, my portable phone, or my broadcast FM radio tuned to KIFM.  So, I am considering the replacement unit to be acceptable. 

My next step is to meet with my neighbors who also have a Safe and Warm blanket (actually a crib mattress warmer) that I suspect is the real source of my ham radio interference.  Now that I know how to get a replacement power supply and have confirmed its effectiveness, I intend to act as an intermediary and get a replacement for them as well...."

Bruce Rogers, KQ6B, Escondido, CA

Photos
Click the Image for a Closer Look.

This is a picture of both the old (non-FCC approved. power supply) and the new FCC approved supply.  The new supply is at the top of the picture and can be distinguished easily from the old in that (1) it has a molded RFI filter on the cable going from the power supply to the dial control, (2) it is smaller and doesn't have ventilation holes in the power supply case and (3) it has an FCC indication on the supply.


This is a close up of the new unit with its FCC label.


This photo shows the old unit without an FCC label.

Provided by Earthsignals.com