Super Regulator

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#2,662
1:10 probe indeed with DC coupling. To be honest I don't know if I'm measuring anything useful at a 10 nS scale. Scope shows about the same with probe connected to nothing. Super reg is totally unshielded, who knows what the scope might pick up? I guess I expected more of a flat line with AC coupling given the specs of the super reg. But it might also be the scope picking up al kinds of external interference (wifi, computer running, mobile devices). The max sensitivity of my scope is 2mV/div, super reg should have way less noise than that, shouldn't it?

Anyway, I was looking for possible oscillation, I guess I didn't see that. DC coupled, I scrolled throught the entire time base of the scope and the line stayed flat (at 10V/div, that is).
 
#2,663
It's not easy to measure this sort of thing. I usually use a piece of coax soldered directly to the SR output and with a BNC on the other end.
At those sensitivities, you find out that the world is full of noise and pulses from all those appliances and light dimmers around.
You definitely have no oscillations.

Jan
 
#2,667
OK, so I built the second one. Voltages as expected. Then I decided to test it with the scope again and accidentally shorted the output of the pos reg with the probe. Small spark. Now the LED doesn't light up anymore. Any ideas as to which part would be dead? Opamp felt hot to the touch, so that one might still work.
 
#2,677
Ok, so here are some measurements and observations; no load on the output.
LED = off
Vout = 26.6V; was 23.98 when it was working correctly (built for 24V)
Vin: power supply output = 32.8V, but when I connect it to the super reg, the input at the super reg measures 26.6, same as Vout.
Voltage at leg 2 of the opamp = 7.06V
Voltage at leg 3 of the opamp = 7.55V
Opamp gets hot very quick, so I measure quickly and then shut the PSU down.

Vref of the LM329 of this one was measured at 6.929V before it was assembled.
 
#2,679
That is the strange thing, there is nothing between PSU and super reg that could absorb 6.2V. The PSU has an umbilical that ends in an XLR connector (female; + - and 0). 32.8 V is measured at that connector between + and 0. I then plug it into a male XLR connector that is connected to the super reg (only + and 0 since it is the pos reg). And suddenly it measures 26.6V ???

Anyway, thanks for your help, I will start with the pass device and see if that helps. Any chance that the output capacitor is also damaged by the sudden discharge?
 
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