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  1. Unitrode produce a switch mode IC specifically for Lead acid charging, the bq2031. If you still want to use one of those PWM ICs you mention you could always have a look at the application note for the bq2031 to see how it works: http://focus.ti.com/lit/an/slua017/slua017.pdf
  2. Presumably output taken from top of C7 in new circuit rather than emitter of Q4, just to clarify.
  3. Not sure I understand about Q1s emitter, looks ok in original cct to me. It is a safeguard against there being no -5v rail isn't it? So when there's no -5v the transistor (Q1) conducts and pulls U2 to ground so there's no drive to the output transistors??
  4. Aha, suppose I must read thru the thread again. Nice photos by the way, I've never made a PCB before but maybe I will try it.
  5. What's the Q2 emitter modification you mention? I've skimmed this thread, maybe I missed something? I've built the Op-amp bits with a pair of TL082s with their supply rail clamped at 22v by a zener. So far so good, but not sure how to change the output stage to give it some voltage gain? Audioguru: thanks for the suggestion for temp sensing with a diode, will have a go at this once I get the PS working.
  6. Could try putting a bulb in series between the rectifier/cap and the regulator. (eg a 12v/21w car brake bulb?). Shouldn't affect the cct at low current but if you get a short it'll light up and take some power away from the regulator!? Haven't tried it mind....
  7. Sallala, before you blow up another transistor...... If you test with a 1 Ohm resistor at 2-3 volts as you say, the 2N3055 will have to disspate a lot of power! (~100W!!) You really need to use more than 1 2n3055 (like in the cct in the thread for the 5A version) and they will need a very effective heatsink!
  8. Don't forget the diodes in a bridge only conduct up to 50% of the time, halving the average current, so you might get away with 1n4000s, wouldn't use the 4001s though as they'd only be good for about an 18v supply!
  9. Hi all, I like the design for this PSU and would like to build it, but with some changes. It seems only U2 needs a high supply voltage to drive the output to 30v, U1 & U3 would be happy with a lower supply voltage. I'm wondering about changing the transistor o/p stage to have a voltage gain of 3 and then clamping the opamps supply voltage at say 20v using a zener so that any stock opamps can be used? (I have loads of TL082s and LM358s etc. so I'd like to use those). I have 2 transformers I can use, a 24v ~100va and a 2x14v ~300va, as this limits the max o/p voltage I thought I'd add a p
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