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Helium

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  1. Did anyone experience how vulnerable DN2540N5 are? They are damaged so easily that I had to scratch my head. E.g. desolder it from a donor known good GRHV, actually new (don't ask why, I had to get spares) and it's detected OK in circuit as N-Ch depletion mosfet. I desolder it, test it and BAM it's no longer depletion mosfet, it turns into kind of Voltage regulator. And doesn't work of course. I spoiled 4 pcs already, despite the fact that I know how to desolder and handle components. And only one out of 5 was OK after desoldering.
  2. I checked phase of all windings prior to connecting. Yes, they are not marked, I marked them by myself. And connected both HVs in phase. Yes, it's single -400 board. The other one (+400) is dismounted ATM and waiting for a part for replacement.
  3. Wait a minute please. I see what you mean. Is the transfotmer up to the task? That's most unfortunate if it's not. Is Star ground of everything a cure?
  4. Thank you folks. Yes, currently GRLV has no ground connection with HV ground. Didn't know that non-tying LV and HV grounds is so critical. Usually it ends up with hum/noise, such sort of things. I will fix that and see. I the mean time I adjusted CSS with GRLV 15VDC to 18mA, so AMP boards are presumably good. Currently amp is almost done, need to replace DN2540N5 on +400 PS.
  5. I've ran into an issue building Carbon. I'm using split PS boards + separate GRLV. When I connect PS boards to transformer (without AMP boards) everything is fine, and voltage is +405/-406VDC (bias is a bit low at 563 but that's non-relevant issue and a matter of zener tolerances). But as soon as I connect AMP boards, transformer starts to heat up a lot (I didn't risk to leave it connected for more that 15 sec). Maybe it will start melting. Here is my connection: +400 goes to each AMP's B+ terminal, -400 goes to each AMP's B- terminal (obviously). However GND from each PS from goes to nearest AMP board only and are not tied together or by a sort of star terminal, therefore GNDs are not shorted. Am I missing a point here? Should connecting GNDs of each split boards remedy the transformer heating problem? Easy to check by yourself, one must say, but one of my DN2540N5 went bad and I cannot check it right now. This is my transformer spec (must be plenty of power, so insufficient VA rating must not be a reason?): 1 x AUDIO GRADE WITH EPOXY FILL INTERIOR PRI:230V SEC: > 2x 330V under load (350mA) (separate windings) > 2x 18V under load (500mA) (separate windings) - VA rating around 300VA
  6. It's normal for 15030/15031. I had the same thing. Amp will work anyway and DC offset will be nulled out. If you are uncomfortable with hfe difference, try using 2sa1930/2sc5171, much closer to each other by hfe. Seem still obtainable if you search.
  7. Wow Soviet) A good old wine) Correct me if I'm wrong, but like AMP series, thread all the way down to gasket (rarely beautifully looking) implies that the gasket is left outside the panel. I usually like to put connector inside the case (this is low voltage Neutrik Speakon, but same idea).
  8. Hi starcat. What are P/N of the connectors and housings and pins you are using? I'm tempted to try these. As far as my quick search revealed, pins and wire entry seals don't come in bundle and are sold separately, aren't they? My concerns is that CPC series seems to be rated for 250VDC/VAC only, and that there is no space between the thread and the gasket, which means that the gasket itself will be outside the panel/case. Any considerations?
  9. Where are you? I've got lots of them, new, maybe 20 of each.
  10. Lol the above board seems to incorporate amb's sigma22)) Unlike Kevin, Ti is definitely not happy when this happens))
  11. Check this video by Haas: You may want a special tapping drill to make thread go deeper in the limited depth of blind hole.
  12. Thanks, I've already start thinking angle grinder FTW to butcher my nice completed T2 PCB. Just kidding, I would do it on CNC if that happened. Kevin, so how do I wire, simply each PS board to each channel (=half T2 board)? I'm afraid I will encounter heavy ground loops.
  13. Quick question. Do I need to cut T2 PCB in halves to separate GNDs if I'm making dual PS, one for each channel (double the number of PS boards and double the number of transformers)?
  14. If you are making a separate +15/-15VDC power supply board (GRLV), you can do with two Bias GRHV PCBs.
  15. If you use MLCC C0G/NP0 grade, I doubt the difference will be audible. Or, MLCC will be even better. At least amb votes for them: https://www.amb.org/forum/about-building-beta24-t3688-10.html?hilit=mica#p34356
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