Maybe that is because low power computer UPS's are so dirt cheap?

A 500 watt one sells for only about $100 at most. they are microprocessor operated, SMD boards and so are made in quantity in China etc... so there is no value in repairing them - imagine repairing a computer motherboard, it would be much cheaper to buy a new one.

Besides which UPS circuits have high and dangerous voltages present and so repair would need a skillful technician, who would charge as much in one hour as a new UPS.

Having said all of that, 6 months ago I repaired my old UPS and sold it.... You don't need a repair manual if you know what you are doing!

Hello mike k:

you may find something on these search pages.

Bearing in mind what Frank787 has said about the high voltages etc.

There was another question on UPS between 1KW and 1.5KW circuit boards, which is what I was looking for on these site. The poster wanted a site with a particular sine wave displayed and circuit diagrams

It really depends on what UPS you have. And by the way my UPS (UK) was over £230.00, $369. I do not call that cheap!.

Can you tell me what Country you are in and what UPS you have?

http://www.google.co.uk/search?hl=en&rlz=1T4GGLJ_enGB294GB294&q=schematic+circuit+of+UPS+of+1KW+and+1.5KW&start=30&sa=N

The most common problem with a UPS will be the batteries require replacement. Anything behond that requires circuit schematics and an isolated scope to troubleshoot. You might get lucky and find a burned out high power transistor or fried component but without schematics you can waste a lot of time tracing circuitry .

Good Luck

Babybear - that is a battery back up circuit you are talking about...

We are talking about an Uninterruptable Power Supply, which supplies 240 volts (or 120 volts) a.c. to keep any equipment attached working during a power cut.

This is a much more complex piece of equipment than your description.

As for the price being as much as £250 for a PC power supply, just look at ebay and the prices for APC UPS's they range around the £50 mark.

Hello Frank787:

This is exactly what it says a Basic UPS Power Supply.

On the site and, linked to either an earlier site I posted or, this one there is all kinds of UPS devices. And all sorts of schematic drawings.

The original poster has not said what UPS they have yet. There is a chance that one of these sights will lead him to what he is looking for. I am just trying to help, thats all. If you do not like what I post, ignore it.

This is not a sight for 'oneupmanship'.

You may have noticed that I gave you a mention for pointing out that these are or, can be pretty dangerous pieces of equipment.

As for price, you pays your money and takes your choice.

http://www.zen22142.zen.co.uk/Circuits/Power/ups.htm

Basic UPS Power Supply <<<<<<<<<<<<<

Circuit : Andy Collinson
Email me

Description
This circuit is a simple form of the commercial UPS, the circuit provides a constant regulated 5 Volt output and an unregulated 12 Volt supply. In the event of electrical supply line failure the battery takes over, with no spikes on the regulated supply.

What exactly you want in terms of output voltage? DC, AC and value?

Wangito.

Hello Mike,

What exactly you need in terms of voltage?. Is it DC, AC and value.

Wangito.

Regards

UPS is a vast-spectrum equipment for power management & also its' techniques;

And its repair & maintenance as much complicated to be discussed in such forums, except

to give some general hints.

It covers from a Battery-back-up to a small Light or Radio set using a diode;

a SuperCapacitor to back-up during the replacement of BIOS battery or like that;

a Large Power Supply [100s of KW] Using Multiple Power-Modules [+system Modules etc ]

of power output 100s of KVA/KW with Redundancy of power to cater for full load even if

1 or 2 modules fail; a back-up- Battery-bank to sustain till the generators are brought

to the scene to take the load.