@Keno – “Yes, heart of the problem is % “the changing of voltage” Right. So stop beating around the bush and tell us what the voltages. Hi, Elektor – I might call- circuit is not bad. Couple of minor modifications made here. Check this out. Item, Type, Manufacturer, Date. Elektor – July/August , Magazine, Elektor – November , Magazine, Unknown. Elektor – October , Magazine.
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High ESR of electrolytic capacitors did you check this? I am also surprised you accepted this an answer.
I would tell you Check some things: Framan – favorite favorite favorite favorite favorite – September 9, Subject: Stop beating around the bush with generalities.
Come on, this isn’t hard. How about contact of the heat sinks? Since this PSU was published by Elektor I assume that some of you might heard or read about this project. I collected Elektor for nearly 20 years but sadly I had to give them away due to space limitations.
When we measured the Op-amps and LM, on certain pins there was voltage also slowly changing.
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What we found out is next – after turning on the PSU, the output voltage rises to certain level depends of voltage potentiometer and than starts elektro slowly descending til 3V.
A common issue is the thru hole lead inductance of cap and ground connections can cause phase shift and if not compensated properly will oscillate. Since you have not seen fit to let us know exactly what is going on, I’ll guess. Never use old capacitors especially electrolytic ones – they don’t age that well.
All eletor these measurements were measured to the common GND of circuit in that part of circuit stabilizer stage.
You can show this on your thesis to demonstrate real world issues. Grounding has a big influence if oscillating at say 10MHz did you scope pin 13 yet? WhatRoughBeast 49k 2 28 Advanced embedding details, examples, and help! Then the voltage changes slowly from 3V-5V. Possible batch of fake LM? Search the history of over billion 1892 pages on the Internet.
I changed Op-amp, LM and a few capacitors every of them but smoothing capacitor – my professor said that it wouldn’t be making such problems. When elekto measured with professor, one pin not sure if 13 was making almost square impulses.
This old design uses external compensation for 2nd order effects which in closed loop Op Amps causes loss of phase margin and can cause oscillation is no margin.
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Now it works perfectly. My LM regulator works well with stable 7.
Paulo Morgado – favorite favorite favorite favorite favorite – February 27, Subject: Be sure to comment elketor finding the defect. Email Required, but never shown.
Mine still has trouble adjusting the voltage. Home Questions Tags Users Unanswered. And if I connect load on the output the voltage slowly descends till 0V everything seems like there should be a capacitor making these problems. In particular Elekyor pins 2,3 must latch for output in linear range which lowers output on pin 6 to cut output. Just what I was waiting for – brilliant! Start by removing the diode from the current limit op amp. I found your data useful but not in the presented form, so I imported into a spreadsheet to align the results in two columns and then imported the images from the datasheet PDF.
I made two of these PSU’s in one housing. And if the voltages are changing, then isolate the section by removing the 3 base drive components R9, D4 and D5and find out 9182 the is acting up.