- amiga history guide Supporting Amiga and compatibles since 1997 -
- banners - disclaimer - faq
- - -
- -     -
recent updates
amiga history
amiga models
internet links



© 1997-2006
Gareth Knight
All Rights reserved



Stop Power Woes

Author: Donald Dalley
Email: ddalley@idirect.com
(c) Copyright 1996, Donald Dalley

Are you willing to gamble thousands of dollars worth of computer equipment on a $5 powerbar?  We can all relate to seeing LED clocks and the VCR blinking at us because of a power disturbance, which barely hints at what actually occurred.  If you have seen lights dim or flicker as your air-conditioner starts running, it is giving you a clue that lots of power has quickly drained from the system.  Similar events can happen at any time and, without protection of the proper type, you are powerless to do
anything about electrical damage.  How common are these disturbances?  A US study covering nearly 40 years quantified what happened electrically at a "typical" location.  There were 443 disruptive or destructive power disturbances; 15 outages, 36 spikes, 128 surges and 264 sags, causing a variety of errors or failures.  There were 3 times as many power outages in
1991 as in 1972.

Do you feel safe with your computer now?  Just how bad is it for electronics, especially your computer equipment?  Do you need an uninteruptable power supply (UPS)?  From my experience, yes, and here is why.  You just can not predict when or with what force power problems will occur.  After two previous experiences with power related damage done to motherboards of a printer and a Commodore 64, I didn't want any power problems to affect my Amigas.  I now use a standby power supply (SPS) for an Amiga 2000, a UPS for the A4000 station, and surge protectors for the C=64, modem and laser printer.  Seriously consider getting appropriate protection, since computer hardware is expensive to repair and down-time could be disastrous.  Amiga stuff may be rare or nearly impossible to replace and your data could be priceless!

Power Absolutely Corrupts

Using a UPS is better than buying insurance because the situation is not could your computer be hit, it's how often or how severely has it already been hit!  If a circuit is near capacity, you may be subjecting it to many under-voltages, the most frequent problem, which could invisibly corrupt data.  Over-voltages can take their toll over time; a spike can kill your computer immediately.  These all could be from something as powerful as a lightning strike, a motor turning on, or as innocuous as warming up a laser printer.  Many problems, except long-term power failure, are local to your building, not from outside.  I often watch a small nearby light dim in rhythm with the heatlamp doing its job inside the printer!  So, depending on what was just turned on, you can see the voltage drop, but chances are these attacks will go unnoticed.  The damage done may not be apparent until later when chips, components, disks or tiny motherboard traces finally fail.

The location of your computer has a great effect on reliability.  If you live near parks, ravines or wooded areas, animals on overhead powerlines can be a big problem.  Industrial areas or certain floors in a big building can have widely variable fluctuations.  Power fluctuations in rural areas are known to be more severe than the ones in cities, too.  With computer
chips using lower voltages and operating at much faster speeds, they are increasingly more sensitive to changes in electricity.

A UPS/SPS is a battery-backed and filtered power source that protects against various power anomalies; spikes, surges, sags (brown-outs) and RF noise, among others, including outright power failure (blackouts).  Sags and surges can be caused by a sudden change in demand from a device being turned on or off.  Lightning, solar radiation, or changes made by a power
utility are more reasons.  The lowly surge is more dangerous the longer or more frequent it is, not necessarily by its magnitude, by accumulating undetected damage.  Superior SPS/UPS models have meaningful surge protection (pass ing ANSI, IEEE and CSA/UL Category A and B tests) to dampen the size of any over-voltage or spike to very small amounts. Figures to look for regarding suppression are the lowest pass-through on over-voltages, and the higher joules number.  The unrated power bar you may be using probably has little or no ability to handle spikes, let alone typical over-voltages.  Cheap powerbars may not even have an overload reset button (similar to a fuse) or isolation between its outlets.  Only higher quality UPSes have brownout protection, preventing some problems such as disk read/write errors.

Another less common power problem is an outright power loss.  This could last for hours, but more than likely it will happen only briefly.  While older analog power supplies can't handle any loss in power, most computer power supplies today have the ability to bridge a gap of a relatively lengthy time.  Depending on quality, most standby power supplies have a power break time of 2-10ms; an uninteruptable power supply has no break at all and is more expensive than an SPS as a result.  Total loss of power (longer than about 10ms) not only loses your data since the last save, but, if writing data to a disk at the time of failure, would cause data corruption and potentially hurt the hard drive media, or worse.  Disk file systems become corrupted if the power failure interrupts a write-to-disk operation.  This means the hard drive or floppy probably won't be recognised when power returns.  The UPS has saved me in this circumstance, too.  At the same time, as power comes back into the system, your equipment could also be hit with a line spike!


When buying a UPS, get one with a large enough power capacity to keep your primary equipment (CPU, monitor and external drives) working until you power down, which should potentially be no more than a few minutes.  An Amiga 4000 could draw 5.0 Amps (depending upon boards, hard drives or extra RAM) when initially turned on.  This is the in-rush current, but most of
the time it will idle much lower, around 1 Amp for a 150W computer box.  An EnergyStar monitor could draw .6 Amp, to well over 2 Amps for coal- fired ones, with a 1084 drawing 1A.  Then you have to consider power used by any other externals and how long you want to run under battery power.

Here is how you calculate your needs:

  1. List all equipment you need to connect to the UPS with their Ampere and Volt ratings found on the back or bottom. You may as well get the Watt ratings, if they are listed, too.
  2. Multiply the Volts (120 in North America) by the total Amp figure to get the V-A requirements for all devices. For example, a system with a draw of 3.3 Amps x 120 Volts = 396 V-A. If you use 220-240 Volts, cut the V-A time in half. If the power consumption is in Watts, simply multiply Watts by 1.43 to get V-A. The V-A duration is the main figure for choosing a UPS.
  3. Catalogues will list battery capacity as V-A or KV-A (1000 V-A) with full-load and half-load durations. Half-loads will usually extend the full-load duration by about 3 times. If you can't find this number, UPS cases have an output (don't confuse with the input rating) Amp and Watt rating on the back. You can compare the total Amps or Watts to see if    your estimate is reasonable. Pick a model that has at least a 25% increase in capability over the total V-A load. This allows longer run times and future increased loads.
  4. Costs vary for battery capacity, component quality, design and features, and customer support. Expect to pay between $120-400 for popular models (from 200 to 650 V-A) from APC, Best, OPTI-UPS or TRIPP-Lite brands.

Save your #%% (CPU)

In real use even small SPSes can handle more than a minimal computer set-up, such as my A2000, 8Mb RAM card, network board, a hardcard controlling two SCSI devices, and a 1084 monitor.  The American Power Corporation's Back-UPS 400 supports a large inefficient monitor and my A4000 with lots of RAM, two hard drives and a network board by supplying
only 3.3 Amps.  Although this is close to its recommended limit, the in-rush does not set off the alarm.  Some laser printer power supplies now have their own MOVs to protect against power surges and don't need to be attached to a suppressor or standby.  My printers, external speakers and modem do not, but they are connected through a powerbar to a separate integrated phone/power surge protector and can recycle when the power returns.

When a dangerous power situation exists, the UPS will warn you with an alarm.  I have been using my computer for months at a time with no indication that anything is wrong.  Then, more than once and for no obvious reason, the alarm has gone off 3-9 times within a few minutes!  Damage and data loss could have occurred with the first hit, as these were more than likely caused by sags or surges.  The lights did not flicker and neither were any clocks blinking at me.  Without the alarm, I would never have
known there was a hit!

My computers have never been powered by a cell for an extended time to know just how long my set-up would run on battery power, nor do I want to be in this position.  Both supplies should be enough to keep things running for less than 10 minutes, which is a long time to be without power.


Although a UPS can be bought in computer and chain stores, there are specialists who can help you accurately assess your needs and sell you power supplies that are not available from discounters.  Commonly, an SPS is mistakenly called a UPS, so make sure you know what you are buying.  Any good SPS, UPS or surge suppressor comes with a computer equipment
replacement guarantee of some sort - higher values are better, of course. Read and keep this guarantee!  Also, find out if the model you want allows user replacement of the battery.  The sealed battery is protected from being drained too deeply (below 10 volts), but don't leave it in a discharged state.  There is PC, Mac and UNIX (no Amiga) software for some models to automatically shut the system down so that you don't lose data if the battery runs out of power.

Don't tempt fate by using computers during a local electrical storm.  If power does go off, turn the power On/Off switch off so that equipment will not be affected by a blast when the power returns.  Be careful if you plug a big monitor or laser printer into the power outlet of the computer; you may be taxing a low wattage computer power supply.  If you transport your computer to a different location, such as a business demo or computer club meeting, take your protection with you!  Don't forget that there is a back-door into the computer through any telephone or network connection; integrated phoneline surge suppressors are readily available.

With the summer storm and air-conditioner season soon upon us, some shocks are coming your way, but by now you know how to keep the computer safe and protected with clean, continuous power.  Inform yourself about your purchases - use this info at your own risk.  Don't hold me responsible if you make a wrong choice and your computer disintegrates in a cloud of

Thanks go to Best Power Technology, Inc. of Canada (800-356-5794), Rolf Stiefel of Power Control in King City (905-933-4327) and North York Hydro for information and their kind assistance.  Prices and phone numbers
are Canadian.

This text may be freely reprinted only in other e-zines or computer club newsletters.  If you do so, please send me a copy of your newsletter.


Latest updates to the Amiga History Guide. (more)

· Amiga Hardware
· Amiga History.de
· Amiga Magazine Rack
· Amiga-news(en)(de)
· Amiga.org
· Amiga World
· AmigaOS 4.0
· Amiga University
· Commodore Retrobits
· Dave Haynie archive
· Lemon Amiga
· MorphOS Support
· morphos-news.de


Other interesting items in the archive!



home · changes · amiga history · features · amiga models
magazines · technical · interviews · internet links · downloads

Hosted by:
Bambi - The Amiga Web Server