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2.0 Electro Static Discharge (E.S.D.)
2.1 E.S.D. - What is it? What does it do?
Static electricity is always being generated around us, even at those times of the year when
we no longer get zapped after walking across a rug and touching something.
Like all state-of-the-art circuit boards, the hot tubs circuit board can be damaged by unnoticed static electricity.
Damaged is the key word. Sometimes a board which has been subjected to E.S.D. will fail immediately upon
being put back into service.
• If the hot tub runs only a few days
, the customer thinks you provided poor service.
• If the hot tub runs only a few months
, the customer thinks the circuit board is a low quality product.
•
The customer loses
use of the hot tub.
You lose money
because you must go back to make it right.
Jacuzzi loses its reputation for quality.
2.2 Avoiding E.S.D. Damage
We can’t prevent static charges from building up within our bodies as we go about our jobs, so we must do
three things to protect circuit boards from getting zapped:
1. Never transport or ship circuit boards
- Good boards or bad boards -
except in static protective bags.
2. Never remove the board from the static protective bag unless you are
ready to install it in the hot tub.
3. After removing the bad board from the hot tub, A) lay it on the ground,
B) remove the replacement board from the static protective bag, C)
lay the replacement board on the ground, D) place the bad board in
the bag from which you removed the replacement board, E) return
bad board(s) in undamaged sealed static protective bags.
2.3 What About Wrist Straps and Special Mats?
The purpose of these devices is to keep the technician, the work surface, and the circuit board at the same
electrical potential, and to drain into ground any static charges which might build up. Proper use of the wrist
strap and special mat guarantees maximum protection against E.S.D. damage.
2.4 Must Wrist Straps and Mats be Used When Replacing A Circuit Board?
No, if you keep the spare board in the protective bag during transport and you observe a few simple tech-
niques during replacement.
The possibility of E.S.D. damage to the circuit board during replacement will be minimal because of the hot
tub’s design and the way you normally work on it. Touching the grounding lug or heater will drain all built-up
static charges from your body much like a wrist strap would. Laying the bad board on the ground will tend to
keep it neutral. Touching a finger to the grounding lug or heater immediately before removing the good board
from the bag will drain any charges built up by the rustling of your clothes. Laying the good board on the
ground after removing it from the bag will tend to keep it neutral. Another quick touch of the grounding lug or
heater before picking up the bad board will again drain built up charges. Slipping the bad board into the protec-
tive bag will allow it to be transported safely. Another quick touch of the grounding lug or heater before picking
up the good board will again drain any charges built up by the rustling of your clothes. In the process of install-
ing the replacement board, you and the board will be grounded to the load box, grounding lug, or heater, drain-
ing off charges you may build up during installation.
