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burrap

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  1. Two transistors gives double the area used to transfer the heat.
  2. Great, we are on to something! If R10 in liquibytes schematic is shorted, this would happen. Can you measure it's resistance? R10 is the 1k resistor which sets the 5mA current for the reference zener.
  3. Whats the voltage drop over your 0.46 ohm sense resistor? It is past bedtime here, can think more tomorrow. But I think it could be current limit. When you remove the voltage trim pot you get really high gain, which means that the input voltage at the rightmost op amp can be low (caused by current limit) and still provide a high output voltage. If the 100k current limit trimpot is connected wrong it will always be 100k. This will mess up the current limit op amp. So I hope the solution is to put a bridge/jumper/short between pin 1 and 2 on the 100k trim pot.
  4. Hi! I have bought the same board from the same man :-) but not built it yet. Ive done lots of simulations though. I guess this is unloaded? Repairman told me about the 100k trimpot, you need to short pin 1-2 there, did you do that?
  5. Oh. Ok. I thought your fix was for the peak that occurs when you are in current limit mode and turn the supply off (since the current limit function collapses faster than the output is pulled down. Then it's ok. Turn on transients shouldn't be as tricky. 0.2 volt on the base of a 2n4401 shouldn't open it, so it should be ok.
  6. I tried simulating this. Works beautifully. I think I had to switch the inputs U1 though. I have the simulation at work. But in this design, Q1 is pointless though. So I will either remove it or modify the negative supply to work with Q1 only. I think I'll go with the latter. Don't need a good neg supply since it's only purpose is to die at shutoff :-) I love getting rid of the neg supply in current limiting mode though. Otherwise I would feel the need to improve it. I will also move most ground connections to go after the current sense resistor. As it is now the 6mA going
  7. I could add that when I was looking for a suitable amplifier I didn't know electronics-lab even existed. So I just browsed for the most suitable class d chip and went on from there :-) It was when I gave up on the 14V PSU idea because of a stronger need for a lab PSU that I found this design and this place!
  8. Yeah but it's a lot cheaper to use a regulator rather than quality caps to get rid of the 100 hz ripple :-) Plus I could make sure it runs on 14 V regardless of load (volume, usb charger etc) and temperature! The two amplifiers I had in mind were 45W and 50W into two channels, with losses and other functionality I estimated 6A.
  9. Hi Liquibyte, I have bought two of your PCBs from repairman2be (rev. 8.), awaiting them any day now. I have studied the schematic pretty thoroughly and tried to read up on the threads. Very interesting, and good to have something educating to do with my time :-). So far I have one question that I can't find a comment on in the forums. First, let me introduce myself. I'm a Swedish 30 year old mmWave/μWave/RF engineer (read: allergic to noise) and I just had a second son so I had to find something to do all the nights I stay up taking care of him. Designing a PSU seems like a good ch
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