Do you have a multimeter? If not, you should get one. Then you can do some measurements to find out what the issue is.
Jan
the voltages are 13.52V but I have now found that the D45H11 (Q3) is frozen, cold (!) while the D44H11 (Q1) is (rightly) hot and the led is on.
the voltages on pins 2 and 3 of the opamp are: 0.6V on the POS side and -0.1 on the NEG side
thanks Giampiero
So there is a problem. The collector is directly connected to the input voltage. How much should the input voltage be? Check that connection.
How much is the negative output, I guess very low or zero?
Jan
Op-amp choice
Following the discussion regarding choice of op-amp for the super-reg, I compared a while ago characteristics of a selection of potentially best candidates for the job, along with the usual suspects. Opamps were selected for both high open-loop gain and high phase margin.
Following the discussion regarding choice of op-amp for the super-reg, I compared a while ago characteristics of a selection of potentially best candidates for the job, along with the usual suspects. Opamps were selected for both high open-loop gain and high phase margin.
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Pin 3 doesn't tell me a lot, there are many confusions in data sheets from manufacturers. That's why I asked for Vcollector.
Anyway, the input at DCin goes directly to the collector. Measure the DC negative input voltage against ground, (pin 1 of J5 against pin 2 of J5), and the collector voltage against ground (collector is where Q3 connects to R8) against pin 2 of J5.
They should be the same, we want to first make sure that the input voltage is getting on the circuit.
Jan
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I guess that is : ... collector against pin 1 of J5>0.0V? Please be specific, otherwise it's hard for me to know what's going on.
Also, remember that '>' means 'greater than'. I don't think that is what you meant.
OK, so now you know that the required negative input isn't there. Therefor, the regulator cannot work.
I assume you have a rectifier and such to make that negative input? How does that circuit look, can you post a pic?
Jan
Also, remember that '>' means 'greater than'. I don't think that is what you meant.
OK, so now you know that the required negative input isn't there. Therefor, the regulator cannot work.
I assume you have a rectifier and such to make that negative input? How does that circuit look, can you post a pic?
Jan
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ok I'm sorry you're absolutely right I wasn't precise.
I am attaching a photo, the R8 is soldered under the pcb because it touched the heatsink so you can't see it and I removed the heatsink to make the measurement more comfortably.
thanks for your patience!
I hope the photo is clear!
I am attaching a photo, the R8 is soldered under the pcb because it touched the heatsink so you can't see it and I removed the heatsink to make the measurement more comfortably.
thanks for your patience!
I hope the photo is clear!
Attachments
That is a very nice comparison, thanks for that!
Clearly the 825 is not the best choice based on this data, although I must admit I have almost exclusively used it because it always works as expected, never have seen any instability or other issue.
So, what would be your own preference now? Have you tested any in hardware?
Jan
So where is that white ground wire going to? I only see one feeding 317 power supply, how do you make a separate pos and a neg input??
Jan
the white wire is GND on the chassis.
But then I have some connection wrong?
the white cable is not connected to 317 .. I must have made a mess I know !!!
I do not want to waste your time but I have collected here and there on the connections to make but sure I was wrong.
I am attaching example of how I made the connections.
But then I have some connection wrong?
the white cable is not connected to 317 .. I must have made a mess I know !!!
I do not want to waste your time but I have collected here and there on the connections to make but sure I was wrong.
I am attaching example of how I made the connections.
