Ken Weitzel wrote:


John Savage wrote:

In my initial post I wrote:

My handheld hairdrier suddenly dropped to half-speed while in use.



In the week since that happened, twice while it has been in use the
speed of the hairdrier has slowly risen to almost normal operating
speed with it running at that speed for about 20 to 30 seconds
before dropping back to half-speed operation. During this normal
speed operation there was a slight odour of an overheating electronic
component (quite different from a burnt rubber smell).

If it was an open circuit diode in the bridge rectifier then the motor
would not operate with reversed polarity DC input like I tested it
with. If it was a short-circuited diode, I'd expect the bridge package
to self-destruct with a bang.

The mystery continues.


Hi John...

Just thinking out loud...

There should be some sort of safety thermostat in there, I think
usually buried inside heater coils. That doesn't describe well
enough - let me say in the center of the air flow, close to the
heater coil.

Possible that the contacts are sufficiently cooked that there's
a few ohms worth, perhaps a bit intermittent?

Take care.

Ken

If the user of the dryer has long hair, and brushes her hair while
blow-drying it, it is not uncommon for deteached hairs to get sucked
into the intake end of the blower. When that happens, they suddenly
wind around the blower shaft, slowing the blower almost instantly. If
they are caught on something and stick in place, the blower shaft will
spin within a cocoon of wound-up hair, and the heat of the friction can
cause the cocoon to heat up and smell funny. As the hairs in the cocoon
burn up, they grip the shaft less tightly, allowing the blower to slowly
speed up.

I ran into this several times when my wife had long hair.

Bill