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My best scrap yard/dumpster finds.

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Bendba:
Hi,

I just wanted to share my last find at the scrap metal yards today. They not long started collecting "e-Waste" so every now and then I go dig through the piles and sometimes find some really good stuff, not free but for scrap price.

What about a "little" power supply?
It's got a very nice main to 24V 40A transformer and another 230/115V to 115V 1400VA transformer. Just a shame the the two sets of 3 output taps are connected together and not separate winding, would have made a nice isolation transformer. Three 100,000 microfards 40V capacitors but I don't know how healthy they are.









I plugged it in to see if it works and measured something rather odd. The output of the transformer is 26Vrms (no load) but after rectification (full wave rectifier), there is only 24.6 V

What happens to the ( Vrms x 2^(1/2) ) - ( 2 x Diode drop)?
Shouldn't I measure around 35V?
I took the leads of the rectifier and measures .47V drop through each diode, no short or open failure.

Vgkid:
If that 24.6v is the output(which seems to be correct, it appears to be a custom telecom supply), then you have a rather good supply. If you cannot use it, someone would love to have it.

bktemp:
The transformer has unusual specs: The label does not say 24V 40A, but for 24VDC 40A, so it is probably rated for at least 50-60A AC but maybe at a slightly lower voltage.
I have no idea why you are getting only 24.6Vdc with 26Vrms input voltage. What happens if you put a load on it? Are the 24.6V reasonably constant? If there is something wrong, the voltage should drop significantly with a load connected.

The cables going to the rectifier also have some strange labeling:
9-50Hz
12-50/60Hz
10-60Hz
What is the output voltage of the unused cable?

Based on the 43/03 and 0311 markings the device was probably build in late 2003.

Based on the connectors labeled FLUID, ANALYSER and COOLING it doesn't look like telecom to me.

VulcanBB18:
Where I work (tertiary education), they often have cleanouts, and in some cases it is ok to scrounge.

Lately, a lab has been having a clean out.  Apart from all sorts of sundry nice lengths of copper cable, there have been all manner of interesting electronic stuff, including a valve-based-on-PCB high voltage control for an electron microscope beam.

Just today I swung past and out with the "good stuff" (they have a "take if you want" sign out, the "not so good stuff" goes in the skip, but still free for the taking) and there were three vacuum pumps out!

I grabbed this one - heavy bugger - I just couldn't pass it up! Score!  8)

cheers,

Bendba:
Hi,
It comes out of what seems to be an automated light absorption spectrometer. I pulled out a few nice little motors with optical encoders, toothed belts, pulleys and rods, going back Tuesday for more, I should be able to get enough out of it to build a CNC engraver frame. But that off topic for the moment.
That's the main power supply for the machine.

The "Fluid", "Analyzer" and "Cooling" connectors are 120V ac outputs.

I get about 21V between the "12 - 50/60 Hz" lead and the "10 - 60Hz" which would make sense, having 26V between the two 50Hz leads.

I did notice the 24VAC making too, so I expected something around 17~18V on the output of the transformer.

I'll have to find a load for it and try again. I'll have to go some digging to find a significant 24V load for a close to 1kW power supply.


--- Quote from: Vgkid on June 09, 2017, 05:21:38 am ---If you cannot use it, someone would love to have it.

--- End quote ---

Don't worry, I'll put it to use, I have a lot of high power projects waiting for a power supply as the best I have at the moment are computer "ATX" power supplies.

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