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Farnell L30 DC Power Supply
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lordvader88:
edit I made an Farnell L30, it's great, posted below



I looked up 1960s power supplies to see how they did it with BJTs, and I got lucky and found this, schematic on p7-1

http://literature.cdn.keysight.com/litweb/pdf/06206-90002.pdf

I have a transformer that does 35V @0.95A from the rectifier. It has a sec. winding that does 12.9V@120mA rectified, its rated for 10.3V @1A .

And I have a 2nd little transformer that does 11.4V @110mA.

So according to LTspice the smaller winding works fine to make that cool reference regulator, it's not center taped but thats ok.

And for the bias transformer I could use the other trans, a TL431 for 5.5V and something for the -2V, I have no idea what most currents should be yet.




I made the model in LTspice, using sinewave soucres, for both windings of my non-CT trans, . I didn't include the meter circuits or the Crowbar on another PCB. But the current limiter is there.

I used 2n3391A/2n2907,  as is actually used in the PSU. I used 2n3055 for the 2 power BJTs. And for the diff. pair I've tried a few high and low gain BJT's. They aren't listed in the manual that I can see. Probably some super matched pair.

I used DC 5.5V and -2V referenced to the output, as the Bias transformer.




So far playing around with the variable resistors, it doesn't seem to work the best, at least it's not very linear at the COARSE voltage adj resistor. Anything over maybe 5K or whatever, and the output is near maxing. I haven'd bothered to add a load resistor, it doesn't idle right.

Also LTspice seems to think 400mA is oscillating through the Current sense resistors. 20mA a piece is going into the 2n3055s. Funny thing is I haven't found where the 400mA exits to ????

I don't know what if anything should be in parallel with R12, so I tried anything under 2k total.

I haven't calculated anything yet, or read the circuit theory, I've been having too much fun making the spice model. I made the diff.amp separate, I should start and try and figure out, if I can, what it should be doing.


I'm going to make it IRL
MarkF:
If you want a comparison, I have a circuit diagram for the HP-6216A power supplies.

   
duak:
I'll bet there's a small error in the schematic somewhere.  A net misnamed or misplaced.

I see that you've put 2N3055 in the voltage comparator - Q1A & Q1B.  I think these should be small signal parts instead.  2N3055s are pretty crappy at low currents.

bd139:
Correct. They are actually dual transistors in these. 2n2219 in LTspice is closest to reality.
lordvader88:
Ok that that never did work in LTspice, and I never figured out the mesh/node equations for the reference area, let alone the rest of it.

Farnell L30


So I found a Farnell L30 PSU and it worked in LTspice, and so I BUILT IT using a single transformer, with all 3 secondaries.

It's on page 11 of this 1, it's the transistor version.
http://www.introni.it/pdf/Farnell%20-%20L%20series%20Bench%20Power%20Supplies


The service manual  is basically this 1
http://rtellason.com/manuals/FarnellL30PsuIssue2.pdf


My reference rail is about 13V at the rectifier, 43V on the primary. And I used the 4.1VAC winding to just squeeze out 4.3V for a 100V 10A  dual meter.

Ii's regulating pretty well at resistive loads, but that's all I've tried with it so far.

I put the transformer in a little wooden box, and put 2 7x15cm prototype boards on top, and I put it all in a cracker box for now. It looks super powerful though.


Alright so I finally built a non-piece of junk 0-30V PSU, it will do for now, without a heatsink and with a single final ouput 2n3055. Under 200mA total is not bad for brief use. Now I should find an old CPU cooler. I haven't pushed it very hard or for long though. The transformer main rail is rated 36Vdc @1.5A. I'm afraid to do that, gets to hot, let alone a single 2n3055. And for now I never ever ever need more that a few hundred milli-amps.

Now I have to try a bunch of math on how this thing really works. Looks fine on the scope at low loads, never tried scope at high loads, I only have 2x 100uF on the 43V winding rect., (I need a lot more assorted caps)


I want to make a comparator circuit with transistors and some 9-10k thermistors I have. I experimented with whats too hot to touch for the 2n3055. I'm sure I could do it with a opamp, but I can't figure out how to do it with transistors, acting on a resistance that drops, rather than a raising voltage.


Now to make a op-amp version, but I'm going to try a curve tracer circuit today
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