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  1. xratedpez

    Noisy Amp Circuit

    For those who might be interested, I did an additional test last night. I swapped out preamps, from a Sony TA-2000f to McIntosh C28. The interesting new finding is that the noise persisted until the McIntosh powered on-- then the noise vanished. The self-powered amps now seem to be working as...
  2. xratedpez

    Noisy Amp Circuit

    Hi Folks, Trying to diagnose a noisy (buzz) in a pair of self-powered speakers - LV1020 by Braun. The buzz/noise comes from the midrange and tweeter only. I've replaced a variety of transistors due to other audial artifacts ("popping") which ultimately was traced to the BC157 transistors...
  3. xratedpez

    Braun LV1020 tri-amped active monitors restoration and noise issues

    Know this is an old post Josh but hoping I can help. The popping/crackling is likely a BC157A (or B) in the amplifier section of the affected channel. I have two of these amps that have exhibited this exact symptom.
  4. xratedpez

    Transistor Substitution Help...

    Does anyone know if any of these transistors I listed above are known to go noisy? I have 3 out of 4 of these units that exhibit the same exact behavior.
  5. xratedpez

    Transistor Substitution Help...

    You are a scholar and a great human being-- thank you!
  6. xratedpez

    Transistor Substitution Help...

    Hi Folks, while transistor substitutions had sometimes been difficult in the past, I'd taken a couple years off from doing restoration work and it seems even fewer through-hole components are available from reputable dealers (Mouser, DigiKey) now. I feel like I've looked up dozens but all are...
  7. xratedpez

    Transistor Sub

    I've uploaded the entire schematic here: https://imgur.com/E9T3tcy The issue is in mid-range circuit. I've replaced all transistors in the pre-amp stage. (I think) I've isolated the noisy transistor to the diode/transistor mentioned above. Lots of older silicon in this unit.
  8. xratedpez

    Transistor Sub

    I would want an hfe in the 'C' band, correct? Does the transition frequency matter for this application? Thanks!
  9. xratedpez

    Transistor Sub

    Here's the schematic, if it helps. Don't necessarily need a metal can transistor (I can adapt the case style). T632 in schematic:
  10. xratedpez

    Transistor Sub

    Anyone have a suggestion for readily available sub for BC341? I've found several but all are either 20 bucks a piece or NLA. Thanks!
  11. xratedpez

    BAX13 Diode Replacement

    Yes! Midrange circuit of tri-amped speaker. I have lots of noise as soon as I turn it on (generally). I've replaced the transistors in the pre-amp section and using a signal tracer (i believe) I've isolated the issue to the D631/T632 section of the circuit.
  12. xratedpez

    BAX13 Diode Replacement

    Anyone know a reliable equivalent to the old BAX13 diode? I've searched this forum and others and haven't turned up anything (which is a new experience for me!) Thanks in advance.
  13. xratedpez

    Transistor Replacement

    I'm not seeing a noise figure listed for the BC171B anywhere. It's an old device, maybe before they listed noise specifications?
  14. xratedpez

    Tube Preamp Transformer Meltdown

    Any tips on where to go for a replacement transformer?
  15. xratedpez

    Tube Preamp Transformer Meltdown

    No, in this unit I kept them as close to original as I could find.
  16. xratedpez

    Tube Preamp Transformer Meltdown

    Hey there! I built the silicon replacement to match the DCV in the schematic (which matched, at least at initial turn-on, the selenium rectifier.) None of those components looked stressed (though I admittedly haven't tested them yet). I used a 5W power resistor.
  17. xratedpez

    Tube Preamp Transformer Meltdown

    Yes. I find myself in the unenviable position of looking for "a needle in a haystack". Thanks for the tip-- I will test.
  18. xratedpez

    Tube Preamp Transformer Meltdown

    Hi Folks, Looking for a little help-- I'd mainly like to get confirmation on an assumption. I have a tube preamp that about 1.5 years ago recapped the electrolytics and replaced the selenium rectifier with silicon diodes. It worked great for most of that time until one night, I accidentally...
  19. xratedpez

    Braun LV1020 Replacement Woofers

    Absolutely perfect. Thank you!!
  20. xratedpez

    Braun LF700 stands mounting hardware information

    This is excellent-- thank you for posting!
  21. xratedpez

    Braun LV1020 Replacement Woofers

    Thanks all! Looking forward to sharing finished products soon-- have been enjoying listening to them a great deal. Question, to avoid potentially lengthy trial-and-error and frustrating trips back-and-forth from the hardware store, does anyone here know what size bolt/screw is used with these...
  22. xratedpez

    Braun LV1020 Replacement Woofers

    I do have some updates-- I've recapped both amplifier circuits and worked out nearly all the kinks in the silicon components. ALSO: I've scored an original pair of woofers (need refoaming-- which is perfect; I can make sure they're done properly) AND a pair of the original aluminum stands. I...
  23. xratedpez

    High Voltage on Speaker Outputs

    The issue is resolved. After setting the bias (they weren't off by more than 15-20%) the turn on thump seems to be a bit better; will keep an eye on it. Haven't had it on long enough to hear the transistor noise but will keep an eye on that too. The best/widely accepted way to troubleshoot...
  24. xratedpez

    High Voltage on Speaker Outputs

    Do the loads need to match what the circuit is expecting (HT=4ohm MT=8ohm TT=4ohm)?
  25. xratedpez

    High Voltage on Speaker Outputs

    Yes- just looked this up. I need to measure with speaker load attached. I've worked on a couple cap-coupled receivers before, but that was about 10 years ago and it's pretty clear I've forgotten. Will attach dummy loads and re-measure.
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