Need linear supply 3.3V/15A or 5V/25A

Thanks, Steve, but meantime we've got one ordered.

--
Regards, Joerg

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Well, your problem is already solved, but you gave me an idea with the above. You've got to stop doing that! :-)

Suppose you re-wound the secondary of a microwave oven xformer for six volts and a bucket of amps?

I haven't done it myself, but you planted the idea, so I may play with it. Get ready to post some of your "sound effects". You're _really_ good at that! :-) You've done a few recently that stimulated some memories, the most painful (but not loudest) of which was turning a

6800 uf into confetti. And yes, I checked the polarity before applying power. And yes, I got it wrong. :-(

Ed

me

t . f .

As it turns out, I didn't get a chance to make a run to Excess Solutions today.

Excess Solutions is great for selling things like calibrators at the price of a simple adapter. I got some HP RF impedance standard for $3. I need to dig it up,but I think it was a "short" that fits the 7mm RF socket.

The tunnel diode pulser was 067-0681-01. It seems heavy for what I believe it contains, which I think is just a resistor and a tunnel diode, and perhaps a trim cap.

I learned a good lesson at ES. They had a nice set of RFI ferrites in a manufacturers sample box; the kind of thing you get for free if the rep thinks you are worthy. All the technical data was in the box. It was by the cash register, and was kind of bulky to carry around. It was $3. Oh, and by the time I got back to the counter, it was gone.....

You're welcome. A great place for cheap power supplies and other surplus stuff. Good to do business with too - I bought their 2KVA variac for a hundred bucks or so. It arrived broken and they sent another without waiting for the broken one to be returned. They even threw in a couple of free hand tools for my trouble.

It has an interesting number and placing of TO3 outlines.

My first thought was that there looked to be 6 identical power resistors in the middle, hinting at load sharing between 6 series pass elements. That seems a tad OTT.

I'd agree that the black blob could be a 723 DIP.

I'd be quite interested in a better resolution image of the board, if anyone has one. It may be a pretty conventional circuit - but it appears to be a fairly unusual physical configuration. The extension of the heatsink to behind the main caps suggest that there are more power devices there (in addition to the main rectifier) - but I can't see where their connection points on the board can be.

As I said, it is always interesting how other designers lay out things!

-- Sue

Sorry, I'm afraid I didn't catch the relation with Yorkshire. I'm located some thousands Km south of that!

Pere

Mine was a 470uF/330V or thereabouts. I was a kid and blissfully unaware that even large capacitors have a finite ESR value. Kilowatt-size power amp and the cap hung on for many minutes. Then the fluorescent lights mysteriously dimmed. But they had no dimmer. What the heck is that?

*BAM*. The cap had decided to turn into a spacecraft. It flew right past my head (no safety goggles), smacked into the plastered ceiling, came down and phsssss ... burned a hole into the carpet. Some white fluff sailed down, like snow. "Son, what was that?" ... "Uh, err, nothing, pa".

Had to replaster that part of the ceiling and buy a new carpet, then lay it. In our family, if you screw up you first try pull yourself out by the bootstraps if reasonably possible. Transporting a 15'*10' roll of carpet on a bicycle over about five miles is something I learned was reasonably possible. Meaning no cop saw me :-)

--
Regards, Joerg

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Those are pretty standard circuits. Ours is still in transit but we've bought many like this before from Condor and so on. There are one to six TO-3 transistors on the back and on "newer" models with their bases and emitters soldered right into the board. For mechanical reasons I don't like that, the old wires were better. But oh well, slim pickens with linear supplies these days unless you roll your own which I always do for the production version.

The circuitry is the classic uA723 veriety with foldback limiting. Nothing special there. On 5V supplies there is often a crowbar but mostly the cheap non-TL431 circuit so the trip point is set above 6V. On other models you get to roll your own external crowbar.

--
Regards, Joerg

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oopere wrote in news:gh8t9k$b1i$ snipped-for-privacy@defalla.upc.es:

Just a little variant of pronunciation will clear it up. :) It's an entirely audible pun so it doesn't worm in text. Just think of how a Yorkshireman might say 'up here'...

What I was commenting on was the /physical configuration/ being unusual

- not the circuit design. eg the size, shape and positioning of the heatsink v the position of the series pass devices.

There will indeed be "one to six T03.." You can see some of them relatively clearly. Looking at the heatsink, I would expect some to have been positioned to the left of centre - but I can't see any there. It could be my eyesight, of course :)

Now there may not be 6 of them - what looks like 6 identical power resistors may not be the what they appear to be.

I do agree with you about the mounting of the TO3s to the board. I hate that too. But again, that is /physical configuration/ - not circuit design. I wouldn't have laid out the components as this designer has, although I may indeed have started from a very similar circuit diagram.

Hence the request for a high resolution image. Not because I am curious about the circuit used - but because I am curious to know where the designer has put things -especially things that I can't identify but expect to be there..

-- Sue

The only photo I could think of is the large unit at the top here but it's not hi-res at all:

All the stuff is there, they placed more temp-sensitive things to the far right where it is cooler. I could take a pic of the power supply next time I am at that client.

--
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Thanks, that's a very kind offer. Although I must confess that it is really just fairly idle curiosity on my side - so please don't waste too much of your time on it.

-- Sue

"oop 'ere"

Ok ;-)

How about a load of parallel LM317's as per LM317 application note with a differential amplifier to measure the voltage drop across the stack used to set the output level of a big COTS switcher so the LM317 only drops a more than whatever the LM317 spec guarantees is adequate?

At least that should cut some of the mass out?

:D

Well, we got a big honking 5V supply and I'll do the usual hack. If I can do it without having to remove the circuit board it'll be done in under 30 minutes ;-)

--
Regards, Joerg

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I hate it when they do that.

I've heard of that filter circuit:

D1 + --->|---+---o B+ | / \\ | | | | | | C1 | | | | / \\ | ^ | | / | \\ | |/ | \\| | Gnd ------+

Now THAT's an accomplishment! Gives "reasonably possible" a whole new meaning. :-)

That "family policy" is great. These days it seems the parents always want to bail out little Johnny instead of teaching him responsibility. What a shame - and what a disservice to one's children. Your family did it right.

Ed

ROFL! That made my day.

Yes, they even buy them new cars nowadays after they totaled #1. My parents never bought me a car and I would have never asked them in the first place. After I got my masters my father wanted to help me with the roughly $2.5k for a used Chrysler but I politely declined. I had enough in my savings after working my tail off.

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I'm goig to post a new thread about rewinding an MOT.

Ed