Lambda LFS-40-12 power supply question

I have a Lambda LFS-40-12 power supply that I want to use for my son's toy railroad. His hobby transformer failed. I pulled this LFS-40-12 from old equipment.

Here's the catalog

I am having trouble getting 12V out of it. I think that terminals S+ and S- and power supply and R+ and R- are remote sensing terminals. I thought that by shorting R+ to R- I would get voltage between S+ and S-, but no such luck.

Any ideas? Is it bad? I checked some voltages, there is reliable 160V DC right after the DC rectifier, on the inputs of big DC capacitors. After that, it becomes kind of murky.

i

Leave R+ and R- open circuit

Connect S+ to Output + and S- to Output minus

The output voltage should be on the output terminals

Dan Hollands

1120 S Creek Dr Webster NY 14580 585-872-2606 snipped-for-privacy@rochester.rr.com

Thanks, Dan and John, no, there is no output with nothing connected to S+/- and R+/-. There is some voltage AC or DC in various places of this board when under power, however.

i

I used another power supply by Digital (one of those $1,000+ surplus supplies), it works okay, but I am very curious about the Lambda supply. It shows some signs of life, and yet no output.

By the way, I have some interesting 30V power supplies (a couple amps, plug into a tube socket), and a few by Power One: 24V power supply, 15 v power supplies, 12V, etc. The Power One ones are rated for about 6 amps. Very sturdily made, regulated, multiple input voltage, blah blah. 5 or so lbs each. I could sell them, after testing of course.

i

usually, the sense lines require to be connected to the output, meaning r+ to s+ and r- to s-.

Finally, there might be an output off switch somewhere.

Rene

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But the sense lines are usually alreade connected internally via small resistors to make the unit operational when no sensing is needed. What is more likeky to happen is that these supplies need a minimum load to operate properly. I have seen that with many off-the-shelf supplies. If you measure them withtout load, the voltage seems to jump up and down and sometimes you can hear the supply make a very slow ticking noise while at each tick, the voltage jumps to maximum.

Simply connect a small lightbulb across the terminals to provide a small load so the supply can start regulating.

Meindert

Also many Lamda's have a "OV" adj, often mistaken for zero volts adj, it is actually an overvoltage crowbar. If set all the way down, you won't get much of an output!