Most amazing dumpster dive ever!!!!

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#42
poobah said:
Find out what that transformer weighs... then compare to others with similar output voltages...
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Good idea. The weight is 35+ lbs, so that would line up best (amongh those I have found) with one listed at 40 lbs and 2.5 KVA!!! 😱

Oh my. . .

I am not quite ready to believe this, but the lowest rating I have seen for a transformer a little smaller than this size/weight is 1 KVA. That being said, I think I should have enough juice to power some op-amps.
 
#46
I'm at an engineering school with good Comp and Electrical programs, but I haven't done much dumpster diving yet. A couple days ago I got a set of four 6x9 car speakers (20W 4ohm, nothing fancy) and some free carpet scraps. Perhaps I'll look around more in a couple of days.
 
#47
My spare trafo was dumpster gold: from a powersupply to a servomotor system. The core is 3"d, 5"h, 5.5"w - looks a little bit smaller than dfdye's, but still should be enough for a chunky LM4702 someday...
 

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#49
dfdye said:
Another for better scale. Does anybody nave a ballpark for what the amperage rating is? Unfortunately the markings are insanely ambiguous and cryptic. My guess is ~3-5 based on size (making it 500VA) but this is purely a guess. I am sure it will at least be able to power a couple of chips! 😀
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What is the secondary voltage?

As for VA, I'd guess somewhere around 2kVA.
 
#51
AudioFreak said:
As for VA, I'd guess somewhere around 2kVA.
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I think we are working our way toward that being the consensus figure. 😀

As for the secondaries, it is a CT isolation transformer, so ~60V.

At least I know it will be able to power the LM4702's I have on order. The max rails it calls for are +/-85, and by my math 60V RMS should rectify to just under 85V DC, so that would be cutting it pretty close. I may throw in a regulator to give myself a little more head room, but at least I won't have to buy a new transformer for my next project!
 
#52
For the LM4702, IMHO you absolutely should regulate the chip's supply (even though PSRR looks good at about 80dB) -- just because the power requirements are minimal and you can comfortably drive the chip at say +/- 70V, and have the output transistors running from the full unregulated voltage.

My trafo seems to be 45-27-0; not quite sure how to use that yet...
 
#53
dfdye said:
I think we are working our way toward that being the consensus figure. 😀

As for the secondaries, it is a CT isolation transformer, so ~60V.

At least I know it will be able to power the LM4702's I have on order. The max rails it calls for are +/-85, and by my math 60V RMS should rectify to just under 85V DC, so that would be cutting it pretty close. I may throw in a regulator to give myself a little more head room, but at least I won't have to buy a new transformer for my next project!
Click to expand...

IMO, Something like that is just begging for a choke input power supply. Would render about +/-51VDC after rectification and smoothing. You also get to use 100% of the AC current rating of the transformer as DC current instead of about 68% for cap input. Not that you're going to run out of current either way with that transformer.
 
#57
example #2 -- this one required new output transistors and the fuse type lamps which All Electronics sells -- otherwise fine and I use it in the photo-lab -- it has been in constant use for about 3 years (that's an Atmel sticker underneath) :
 

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