GoodSoundClub - Romy the Cat's Audio Site

In the Forum: Audio Discussions
In the Thread: It’s mad, mad, mad... electricity.

Post Subject: Herman's unfortunate experiencePosted by PurePower on: 5/26/2009

The failure Herman had was probably on the input side - not the output.

You will notice 2 things.
1. The system operated normally for 6 months, so it is unlikely an overload issue.
2. The PurePower did its job of protecting the audio equipment (self sacrifice is the first rule of power protection).

The failure was most likely the result of a high voltage transient causing a short circuit of a PurePower input power supply high power mosfet chip.
The description is consistent with a mosfet short. They can fail with a bang. This results when the mosfet is subjected to an input voltage over 450V.

We have documented that utility power frequently contains transient voltages of up to 700 volts that are very short duration - typically less than a
millisecond. They are caused when the utility switches in or out large capacitor banks they routinely use for power factor correction - a necesary
function of power distribution especially in industrial areas. On site testing for power quality at a Purepower customer site in Connecticut by an
independent power quality engineering firm captured a number of these "transient events" over a 3 week period. (We are working of providing this
report in a white paper.)

Normally these high voltage short duration events are too fast to even cause a light to flicker - and certainly are way too fast to trip a fuse, but our
mosfets in the 1050 were super sensitive to sudden overvoltage - and thus were susceptible. Most consumers don't run into this problem or the transients in their neighborhoods are lower voltage - but it only takes one transient and a fraction of a millisecond.

We addressed this problem in late 2008 - and made changes to our 1050 motherboard. Now all 1050 2009 production is as immune to transients as our
model 700 and 2000 always have been.

Not only that - the transients cannot pass through the PurePower double conversion - unlike other types of power conditioners which allow transients to reach
sensitive audio equipment after passing right through. We have no doubt that some audio component power supplies can be harmed
in the same way our PurePower input power supply was.

As to Herman's preference for utility power sound after his unnerving experience, I can understand. We sincerely apologize for giving him such a fright.
But I bet in a blind test he will prefer to go back to listening with PurePower.

Richard at PurePower

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