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sorenb

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Posts posted by sorenb

  2. Closed - KGSSHV Carbon and GoldenReference HV PS Group Buy

    in Do It Yourself

    Posted

    Just a heads up!

    I asked Kevin to do a split version of both the Golden Reference HV without the Bias supply, and with the big caps be off board for direct chassie mounting. Also asked for a split version of GR LV, and asked Kevin to do a Bias Supply that have both PRO and NB. Finally I asked Kevin to do all boards less than 2U(80mm) in width 

     

    The HV PSU has always been made of two positive PSUs in series, so the only difference between a +/-HV and two +HV in series will be the PCBs are cut in two.

    In rgrds to LV PSU, Kevin has done a real complementary negative PSU for the GR LV, but according to Kevin there are no advantage/disadvantage to use two postive LVs in series to get +/- LV.

     

    So as far as I can see, the positive single PSU boards gives everybody more fleksibility in terms of how to mount in a chassie, without any real disadvantage (apart from a bit of extra wire).

    I am pretty sure that Kevin can be pursuaded to do a 'usual' LV (78/7915 type) for those who prefere that to the Golden Reference LV.

     

     

    I suggest that the GB offers either the full PSU (HV/LV/Bias/caps onboard) or Single HV (caps offboard), single LV, Bias(w. PRO & NB) 

  4. HV delay

    in Do It Yourself

    Posted

    I don't really see why it shouldn't work feeding with a CSS (that should even protect the tubes) and trigger on the voltage across the tube heater ... rather than using a timer delay???

  6. HV delay

    in Do It Yourself

    Posted

    that's the implication but it could just be the effects of the startup sequence. I don't think others with the Megatron are delaying the HV by 5 minutes

    Just had a go at the KGST ....it swings to +rails at turn on, after 8-10s it drops quickly to some 20-40V ....and reaching 0V in additional 10s

    have you measured the behavior of your (magnificent Megaton btw)  from startup until it settles?

  7. HV delay

    in Do It Yourself

    Posted

    duly noted. I guess I need to implement the HV mains delay then? without the delay there's some swishing sound that takes around 5 minutes to settle out

    does it take five minutes for the heaters to reach a steady state? 

  8. HV delay

    in Do It Yourself

    Posted

     ....is it a bad Idea to feed the heaters from CCS and trigger on the voltage across the heaters? ....I measured the voltage drop across the heaters in the KGST ....(I have .47 ohm in series) it jumped right up at 1,6V and then slowly dropped to 0,5V and stays there ...and it seems to translate into the outputs swinging up to +rail ...and then begins to drop to zero after a while

    I guess feeding the tubes from a CCS feeding 1amp will make the voltage across the heaters go from ~2V to ~ 6V .... then use a simple latch that triggers at ~6V to turn on the HV 

     

    if several heaters of different tubes are at play one might use a master trigger controlled by some AND-gates making sure that all heaters has reached working state

     

    ....is it just a bad idea from some reason?

  12. Closed - KGSSHV Carbon and GoldenReference HV PS Group Buy

    in Do It Yourself

    Posted

    See attached image for a sketch for both 388 and 288 cases. There isn't much room for error, unfortunately. Even shaving off 1-2mm off the boards would help them fit. They will likely fit as is, though (maybe with Kapton tape along the back and front panels, since they will touch the boards). Since we just barely started discussing transformer specs on the main kgsshv thread, it's hard to know what SumR or Toroidy can do (or if r-cores make more sense, and how large they need to be).

     

    If the whole thing can fit in a Galaxy 288, then with 5cm sinks on both sides, the entire amplifier will be the size of a Galaxy 388 case, which is quite compact. That said, even a 388 with sinks is fairly reasonable. It'll fit on all but the smallest desks.

     

    As for sinks, I would be delighted to find ones angled upwards, like on Justin's BHSE.

    if you are using the single HV/LV boards with chassie mounted caps...you might find it easier to get a fit inside the small Galaxy ...

    HV single: 3x4.11

    LV single:3.72x2.4

    Bias:3.56x2.0 (including NB)

  13. HV delay

    in Do It Yourself

    Posted · Edited by sorenb

    Just an idea since your circuit is already 555 based .... how about feeding the heaters from a CCS  ....and have the 555 coupled as a Schmidt Trigger ...starting the HV when ever the voltage drop across the ´heater is less than some voltage?

    Then the heaters will not pull excessive current and warm up gently ...and when ever warmed up the 555 will trigger the HV...

  17. i'm on a roll... the kgsshv

    in Do It Yourself

    Posted

    Pretty certain he means the two 390kOhm resistors. For 450V you'd sub in two 440kOhm (or any two that add up to 880k).

    I guess that is obvious .... but not that obvious that you need to maintain 10v across the resistor  that is currently 20k ...it might be higher/lower as far as I can figur out.

  19. i'm on a roll... the kgsshv

    in Do It Yourself

    Posted

    I would definitely go with the 550v caps.

     

    depends on the voltage range of your power.

     

    if you go with standard voltage +/-5% you might squeeze in to the 500v

     

    but if its standard voltage +/-10%, that's pushing it.

    So if 500V or 550V is needed one needs two times the cap in order to be able to serialise and still maintain the capacitance?

  20. i'm on a roll... the kgsshv

    in Do It Yourself

    Posted

    change the value of the 2 resistors in series  on the other side of the reference.

     

    the 47uf are tantalum capacitors, and 35v is fine. just in case the zener has to go up to 24v

    might be a stupid question, but don't you need the 20k resistor to maintain a drop of 10V?  something like (Vcc-10V)/0,5mA = total value of two resistors in series ?

    so in case one cannot get the resistor values needed, the 20k can be changed a bit up/down as long as there are 10V across ...right?

  22. krell ksa5 klone

    in Do It Yourself

    Posted

    *LOL* old love never dies .... those calculators either Texas or HP did quite an impression on most back then ....had a pow whom I studied togther with....bought a HP went home ...and had an accident with his car ....got off road and ended in the middle of a field ..he cannot remember much apart from the first thing he did was open the trunk and test he newly bought HP calculator ;o)

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