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  1. AHHH!!! Got it. By using only 0-36V the current flow has to go from +Vin to -Vin. The only way the circuit would work as it is now is if the current flow from +Vout to 0V was equal to -Vout to 0V (meaning the resistance of the positive load was equal to the resistance of the negative load). The bigger the current mismatch between + and - the more my "0V" would move toward one pole or the other. Thanks for taking the time!!!!! Kevin
  2. Hi Hero That's really the central question. I don't understand why the 36V doesn't balance itself in the circuit? Even if I gave the input +/-18V with a 0V reference the whole input would still be floating. What would prevent the input from being pulled down the way the 36V is?
  3. I've implemented the changes that you suggested. Q1 is now a TIP41 (NPN) with the collector to Vin and the emitter facing the sense resistors. Q3 is a TIP42 (PNP) with the collector and emitter swapped as well. The circuit is still showing the same readings. The voltages on the input are pulled off center (+12/-24 VDC). The output still tracks although it is much lower than expected. Could you explain why the input voltages aren't centered around the ground as I would have expected? Could you elaborate on the earlier comment "the uneven voltage distribution seems very even"? I've checked the outputs of the opamps. None of them are driven to the rails. Thanks, Kevin
  4. Q1 is a PNP and Q3 is NPN with the collectors on the output side. I do have current sense resistors between the collectors and Vout, but that scheme should still work. Vset and Vsense are fed into opamp U3C. If Vset > Vsense the output goes a little higher, forcing more current through CE of Q2 and BE of Q1 which in turn causes the Voltage across Q1 CE to drop increasing Vsense until Vsense = Vset. If I'm looking at something the wrong way please let me know. The circuit does respond to changes in the Vset and Iset. My main question is still why doesn't the input voltage center around the ground (J2-2)? Thanks again for all the help! Kevin
  5. J1 is the input at 36VDC (floating) and J2 is the output. J2-2 is the gnd. Q1 is a TIP42 and Q3 is a TIP41. Kevin
  6. Sorry. I didn't follow that at all. I didn't replace the opamps but I have no real reason to think any of them are bad. I also don't think any of the them are saturated. If I change the value of R35 I can vary Vout (and it tracks on -Vout). I'm willing to look to see if any of the opamps are saturated but I'm not sure how to go about that. I'm also not sure how to interpret "the unevn voltage distribution seems very even". Could you elaborate? Kevin
  7. Hello Everyone: I've designed and built a Dual Tracking Supply circuit (Schematic attached as PDF). I feel like I'm too close and am either not understanding, or missing something that is causing my confusion. I'm hoping somebody can take a look and set me straight. I'm feeding the circuit 36VDC (floating) at the input and am seeing some measurements that I do not understand. Measuring everything with reference to pin 2 on the output terminal (the nominal ground of the circuit) I get +Vout and -Vout within about 0.2 V but it is only about 2/3 the value I expected. I expect to see around 17.5V but only see 12.5 What bothers me more is that value I see at the top of Z1 and the bottom of Z2. I expect those to be about +12V and -12V respectively. What I see is about +6V and -12V instead. Similarly, on the actual input terminals of J1 I see +12V and -24V. I really don't understand why the voltage is not distributed evenly? Although this explains why I'm not seeing full voltage at the output. So I figure that something in the circuit is pulling the voltage down but I don't know what it is. I'd read in some forums that you should put a resistor in place instead of tying an op-amp input to ground so this is why I put R31 in place. I thought I misunderstood it's purpose so tied some clips in place to remove it. While that had no effect on the circuit I had initially made a mistake and had tied pin 9 of U4 (the inverting input of the same op-amp) to ground instead. This mistake did make the circuit appear to run correctly although the regulation between +Vout and -Vout was significantly worse. If the point between the Vout sense resistors (r32 and r33) is supposed to be tied to ground, I'm not sure what the purpose of opamp 4c is at all. Anyway, any and all help, suggestions are VERY welcome. Kevin PowerSupply.pdf
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