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  1. Replies
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    All I said was OK, fine, it doesn't matter....

    All I said was OK, fine, it doesn't matter. That's not a question.
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    214

    I think I'd say that a different way. In this...

    I think I'd say that a different way.

    In this circuit, the pot is DC blocked at the wiper and has one end open. There can be no voltage >difference< across the pot, as it all floats at the same...
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    388

    It's possible that you were on the edge of...

    It's possible that you were on the edge of motorboating. This is the low frequency equivalent of high frequency oscillation. You sometimes run into it if you keep increasing bass response in the...
  4. That is 100% true. It's CIRCUITS that affect the...

    That is 100% true. It's CIRCUITS that affect the sound.

    I'll insert my standard complaint about anecdotes: reputation is interesting, but by no means definitive. You can't measure reputation, and...
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    312

    It's an interesting case in imponderables. I...

    It's an interesting case in imponderables. I think you're right J.M. - the real threshold would be when you get arcing to another electrode. 300V would be a good guess. Probably this varies a lot...
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    468

    Sticky: Correct or not is hard to say. In an amp with no...

    Correct or not is hard to say. In an amp with no feedback from the speaker output, there is no particular reason to ground the speaker leads for the circuit's operation. You can ground one of them,...
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    787

    The design of the E-I lamination and coils makes...

    The design of the E-I lamination and coils makes the magnetic field run along the length of the center leg of the E, then return through the outer legs of the E. Think of the field orientation as a...
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    858

    Were you measuring your 400V at the first...

    Were you measuring your 400V at the first 22uF/450 or the second one?

    I guess, put another way, what are the current (sorry, meaning now) voltages on both caps.

    If the event opened the OT...
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    858

    A transformer with 750ac across a ct high voltage...

    A transformer with 750ac across a ct high voltage output makes 375vac on each half secondary to be rectified. The UNLOADED voltage when rectified is 530Vdc peak, which agrees well with your 513...
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    989

    There is one more step in the humdinger...

    There is one more step in the humdinger evolution. I'd have to go looking for where I saw this, but it was clever.

    There may be some level of hum you just can't get rid of by reasonable means....
  11. First, get that shorted speaker out of there....

    First, get that shorted speaker out of there. These amps don't have any clear protection against shorted outputs, and you could melt down the output transistors pretty easily. In fact, you have...
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    989

    If you're going for the "artificial center tap",...

    If you're going for the "artificial center tap", yes, that works. Two 100R resistors in series, across the whole 6.3V winding, with the center connection between the two resistors tied to ground. The...
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    I'm still a little confused by the question, but...

    I'm still a little confused by the question, but maybe I can add some useful data.

    Is what you're thinking about an attempt to get lower hum? If so:
    > You have to have some kind of reference...
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    902

    Yeah, give them a try. You're actuallyl buying...

    Yeah, give them a try. You're actuallyl buying Newark's assurance that these are quality devices. I trust Newark that much.

    @juan:
    Yeah, they were intended to replace TO-66s. I suspect that...
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    989

    The "has spare capacity" on a 5V winding might be...

    The "has spare capacity" on a 5V winding might be a problem. If the 5V winding is powering a tube rectifier, nearly all tube rectifiers have the cathode connected to the heater. It floats on B+ in...
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    902

    Wow! They're still around! Neat. I was...

    Wow! They're still around! Neat.

    I was expecting him to find a few on ebay for $50 each. I did a few amps early on with 40409/40410, and fixed a few others. The industry zoomed right past that...
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    Add to or mess with the values on the Zobel....

    Add to or mess with the values on the Zobel. Can't hurt, can it?
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    989

    Possible? Sure. You'll run into several...

    Possible? Sure. You'll run into several difficulties, all of which are relatively well known. There are solutions for them, though.

    The 6.3V/3A winding can be full wave rectified into 6.3V*1.1414...
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    Oh. If the drivers are the 40409/40410 types and...

    Oh. If the drivers are the 40409/40410 types and are damaged, don't even try to get exact replacements. The combination TO-39 device and pressed on heat sink are unique. Count on using TO-220 devices...
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    The amp uses +/- 40V power supplies, total of...

    The amp uses +/- 40V power supplies, total of 80V. Use devices rated for at least twice that, 160V, preferably more.

    A good, safe choice would be the On Semi MJ15022 or MJ15024. There are others....
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    Good for you. Your riddles are Mother Nature's...

    Good for you. Your riddles are Mother Nature's way of telling you that you would really, really enjoy some more electronics learning. Go for it! A few answers to questions in a forum won't do the...
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    The picture of caps mounted up high on springy...

    The picture of caps mounted up high on springy leads over a built-in capacitor roaster resistor is about as bad a way to mount them as I can think of. The failure rate ought to be high on that. The...
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    It seems to be "My amp blows fuses! What could...

    It seems to be "My amp blows fuses! What could POSSIBLY be wrong with it??" season again. I just typed much of this in at another forum beset with "fuses-blowing" problems, so I'll try to reconstruct...
  24. Thread: DC DC converter

    by R.G.
    Replies
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    660

    @ Soulfetish: Good thoughts. Doing a good...

    @ Soulfetish:
    Good thoughts. Doing a good design of a high frequency switching converter does require a lot of picky considerations. Especially where to get small size, you run your switching...
  25. Thread: DC DC converter

    by R.G.
    Replies
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    660

    How does the ripple voltage react to loading? ...

    How does the ripple voltage react to loading?

    Many recent switching controllers react to too-small loading by going into "hiccup" mode, running a blast of pumping to raise the output voltage,...
  26. Thread: DC DC converter

    by R.G.
    Replies
    16
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    660

    30-40v sawtooth ripple? What frequency is the...

    30-40v sawtooth ripple? What frequency is the ripple?
  27. Thread: PCB grounding

    by R.G.
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    Ah, grounding. :) For your limited case, it...

    Ah, grounding. :)

    For your limited case, it will probably not matter.

    At audio frequencies, what matters in grounding is what >ground offset voltages< are generated by >ground currents<...
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    Do what the high power radio guys used to do: put...

    Do what the high power radio guys used to do: put a load resistor into a can of oil. Drive it with the output signal and the measure the temperature rise of the can of oil. This is probably best done...
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