Problem with negative ALW superregulator

[Jaap]

I tested the regulator but i might have made the connections from a power supply which was powered off but accidently still had a voltage at the output (big capacitor at the output).

The manual states that this will damage components permanently.

The regulator doesnot work. What components will be damaged (AD825 opamp ?), can I check this ?

[janneman]

Originally Posted by Jaap

I tested the regulator but i might have made the connections from a power supply which was powered off but accidently still had a voltage at the output (big capacitor at the output).

The manual states that this will damage components permanently.

The regulator doesnot work. What components will be damaged (AD825 opamp ?), can I check this ?

Hi Jaap,

Maybe you can do some targeted measurements before indiscriminately replacing components wholesale?
Check the supply voltage of the opamp, is it there? If this is the reg that supplies the opamp from the output, temporarely feed the opamp and reference from the input voltage (if it is not too high) and check the ref voltage and the opamp output voltage as well as the voltage difference between the opamp inputs. Does the opamp seem to work?
Maybe first check the pass resistor for any shorts between the terminals, and correct diode 'resistance' (0.6V) between C-B and E-B.
Do you have a schematic?

jan didden

[Jaap]

Originally Posted by janneman

Hi Jaap,

Maybe you can do some targeted measurements before indiscriminately replacing components wholesale?
Check the supply voltage of the opamp, is it there? If this is the reg that supplies the opamp from the output, temporarely feed the opamp and reference from the input voltage (if it is not too high) and check the ref voltage and the opamp output voltage as well as the voltage difference between the opamp inputs. Does the opamp seem to work?
Maybe first check the pass resistor for any shorts between the terminals, and correct diode 'resistance' (0.6V) between C-B and E-B.
Do you have a schematic?

jan didden

Here is the schematic, R6 left out (wirebridge)
Opamp is wrong in the schematic, I use AD825
transistor is not D45H8 but D45H11
gr Jaap

[janneman]

Originally Posted by Jaap

Here is the schematic, R6 left out (wirebridge)
Opamp is wrong in the schematic, I use AD825
transistor is not D45H8 but D45H11
gr Jaap

OK, did you check the output of the pre reg? Is the LED D2 lighting?
Check that Vsense is conneted to Vout, and that the various Gnd and Gnd sense wires are connected.
What is the voltage at the opamp inputs, if you connect the opamp supply temporarily to the pre reg output (if not too high for your opamp).

BTW What is the problem? No output, wrong output?

jan

[Jaap]

Originally Posted by janneman

OK, did you check the output of the pre reg? Is the LED D2 lighting?
Check that Vsense is conneted to Vout, and that the various Gnd and Gnd sense wires are connected.
What is the voltage at the opamp inputs, if you connect the opamp supply temporarily to the pre reg output (if not too high for your opamp).

BTW What is the problem? No output, wrong output?

jan

prereg is o.k.: I have checked the regulator without the prereg
green Led is not lighting
Vsense is connected to Vout, grnd sense also connected to ground

I had no outputvoltage, I will check the voltage of the opamp input tonight.

I suppose I had too much voltage at the input of the regulator, maybe 20 volts or so and without all the connections.
I thought the PSU I used for testing had no voltage because it was shut off, but I was wrong because the capacitors still had current.

[janneman]

Originally Posted by Jaap

prereg is o.k.: I have checked the regulator without the prereg
green Led is not lighting
Vsense is connected to Vout, grnd sense also connected to ground

I had no outputvoltage, I will check the voltage of the opamp input tonight.

I suppose I had too much voltage at the input of the regulator, maybe 20 volts or so and without all the connections.
I thought the PSU I used for testing had no voltage because it was shut off, but I was wrong because the capacitors still had current.

I see that the prereg is fed from Vout so it's all chasing it's own tail.
The first step would be to make sure you have some input voltage on the reg itself, after the pre reg. It might well be that the pre reg is blown. It should have a reverse diode from out to in to be safe for exactly what you had.
So, either replace the pre reg right away or run the reg without the pre reg just feed it directly from the input power.
What's the Vin and Vout this should run on?

Edit: I read your post again and you've lost me.
What means: pre reg is OK? How did you check that?
If you say: I tested the reg without the pre reg, was it OK then or not?

jan didden

[5th element]

Shouldn't the pre reg maintain a voltage difference of around 2.5 volts between the output of the pre-reg and the output of the super reg? I guess if you varied the input voltage, if this voltage difference remained constant it would confirm that the pre reg is working.

I had trouble getting my super regs to work too, also from the schematic drawn up by ALW. Regardless of if the main regulator was working, the pre reg always maintained this same voltage difference.

I am hesitant to recommend powering the main regulator without the pre reg, that is if the pre reg is working, as far as I have understood the pre reg is what gives a degree of protection to the main regulator, protecting against short circuits and vast over current conditions.

I will say one thing however, during all of my fiddling about with the circuit I never once destroyed a component and I must have abused things pretty badly.

I will echo what Jan has said though about checking the diodes and also checking to see if the voltage reference is giving you what you expect. The problem I had was with the voltage reference, a stupid mistake, I had it in the wrong way around - 'as viewed from below' I finally saw, printed in very small text next to the devices pin out diagram - DOH!, not viewed from above. I swapped it round and hey presto it all worked.

The LED remained unlit with the voltage reference around the wrong way, it would flash very briefly sometimes when the thing first powered on, but nothing more. I will also add that it might be worth checking the resistors that set the output voltage. If it's set too high, say 19 volts and you're powering it from 20 volts, that too can prevent the LED from lighting up. What voltage do you get on the output?

[Jaap]

Originally Posted by janneman

I see that the prereg is fed from Vout so it's all chasing it's own tail.
The first step would be to make sure you have some input voltage on the reg itself, after the pre reg. It might well be that the pre reg is blown. It should have a reverse diode from out to in to be safe for exactly what you had.
So, either replace the pre reg right away or run the reg without the pre reg just feed it directly from the input power.
What's the Vin and Vout this should run on?

Edit: I read your post again and you've lost me.
What means: pre reg is OK? How did you check that?
If you say: I tested the reg without the pre reg, was it OK then or not?

jan didden

Sorry, to be unclear.
I did disconnect the prereg from the regulator. After that i tested the regulator by feeding an input voltage directly into it.
I also did the same with the disconnected pre reg to see if the LM337 was O.K. This part is working.

R8/R9 is 887R/1K2 so the regulator will deliver about -12 volt.

[Jaap]

Originally Posted by 5th element

Shouldn't the pre reg maintain a voltage difference of around 2.5 volts between the output of the pre-reg and the output of the super reg? I guess if you varied the input voltage, if this voltage difference remained constant it would confirm that the pre reg is working.

I had trouble getting my super regs to work too, also from the schematic drawn up by ALW. Regardless of if the main regulator was working, the pre reg always maintained this same voltage difference.

I am hesitant to recommend powering the main regulator without the pre reg, that is if the pre reg is working, as far as I have understood the pre reg is what gives a degree of protection to the main regulator, protecting against short circuits and vast over current conditions.

I will say one thing however, during all of my fiddling about with the circuit I never once destroyed a component and I must have abused things pretty badly.

I will echo what Jan has said though about checking the diodes and also checking to see if the voltage reference is giving you what you expect. The problem I had was with the voltage reference, a stupid mistake, I had it in the wrong way around - 'as viewed from below' I finally saw, printed in very small text next to the devices pin out diagram - DOH!, not viewed from above. I swapped it round and hey presto it all worked.

The LED remained unlit with the voltage reference around the wrong way, it would flash very briefly sometimes when the thing first powered on, but nothing more. I will also add that it might be worth checking the resistors that set the output voltage. If it's set too high, say 19 volts and you're powering it from 20 volts, that too can prevent the LED from lighting up. What voltage do you get on the output?

All components are placed well. I used the official ALW boards and manual with pretty good documentation.
Input voltage was hight enough.
A positive regulator that i tested on exactly the same way is working o.k.

[5th element]

If you have a positive working version it is quite strange that the negative one doesn't. There are very few differences between the positive and the negative versions.

From memory the only components that require a differently wired circuit are the opamp and the pre regulator, everything else shares exactly the same pin out, the only thing necessary is reversing the polarity on the diodes/caps/voltage reference.