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Helium

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Posts posted by Helium

  1. The Multi Amp aka Dynalo Mk2

    in Do It Yourself

  3. The Multi Amp aka Dynalo Mk2

    in Do It Yourself

    Posted

    Try Metcal PS-900. Clearer better than Hakko 888d (I have both). Hakko 888d is a great station, but sorry to say, Metcal is better. Reason I still keep Hakko is that I already invested in lots of Hakko tips, including so called 'microwave' tips which I use for soldering SOIC packages and the like (when heat transfer speed is not critical). But most of soldering is done by Metcal, including joints to heavy ground planes.

  4. Balanced to unbalanced board

    in Do It Yourself

    Posted · Edited by Helium

    To be honest, modern BC546/556 from ON are measuring like crap. Last lots I bought (genuine of course) measured Hfe 250-280 @ 10uA base current, some hardly reaching 300.

    Try to get from AMB his NOS stock from Fairchild. As I remember they measured 300-330 and up consistently. If I recall correctly, BJT transistor leads from amb didn't magnetize as well.

    Now I feel sorry that I didn't have time to order and have them shipped from him for my CFA amp which is in progress.

  5. Balanced to unbalanced board

    in Do It Yourself

    Posted

    On 05.01.2018 at 6:24 PM, sbelyo said:

    2. The highest hfe is the BC546\556 C, this only comes with formed leads.  Will I need to straighten them out, and if so I'm guessing there's no issue with that?

    No, formed leads are what fits best for this board (though looking at the PCB you might think that lead spacing is for straight leads. No, it for formed.

  7. krell ksa5 klone

    in Do It Yourself

    Posted

    Did anyone run KSA5 at 30VDC?

    I like all my dynamic amps running at 30VDC.

    I'm scared a bit to fire it up. Don't want to fry anything. Balanced version was more difficult and expensive to make than I expected.

    P.S. I'm using OPA445 and G5V-2-H1-DC24 relays. And all other components are according to BOM and PCB silkscreen.

  9. goldenreference low voltage power supply

    in Do It Yourself

    Posted

    On 20.02.2017 at 12:21 AM, mwl168 said:

    Another two GRLV live! These are set up for 20VDC rails to power my dual-mono SS Dynalo.

    Thanks to Pars for his creation and generosity of sharing the Schottky bridges with a built-in AC snubber. Although I have to settle for the LM4040 VREF for now until I get the LT1021.

     

    GRLV with Schottky bridges.JPG

    schottky bridges.JPG

    Pars, any chance you have more rectifiers left? I'd like to try them out on one set of GRLVs.

  11. Part Sourcing Assistance/Advice Thread

    in Do It Yourself

    Posted

    13 hours ago, mypasswordis said:

    Yes that is the one I was looking at getting, have you tried it with any non Molex connectors and does it crimp both wings at the same time or one at a time? If both, can you measure the exact width? I was thinking of CNCing my own die but realized it may not be as simple as I first thought.

    In other news, I just got off the phone with a service rep at arrow who had a quaint Southern drawl and I accidentally switched to my approximation of one halfway through the convo. 

    Yes, it crimps both wings at the same time. First you crimp conductor (wire), then you crimp insulator with larger die that is close to holders.

    I was looking at Engineer PA-09/20 as well, but it doesn't have separate die for crimping insulator.

    Regarding width, I cannot measure it at the moment. But I always use Molex, e.g.lock header 22-11-2022 + crimp terminal connector 0008550131/0008550130 + lock housing 0009508023. Fits perfectly.

    I also used it with TE Connectivity connectors which are Molex analogue.

    • Thanks 1

  15. and now for something completely different part 3

    in Do It Yourself

    Posted · Edited by Helium

    On 25.11.2017 at 6:36 PM, kevin gilmore said:

    that is probably close.  ksa5 has a fet input stage.

    Kevin, still I have a question about input impedance. Maybe I don't get it right.

    There is a diffrence between schematic and PCB silkscreen.

    Schematic says R17 is 10K (=input impedance). Board silkscreen says R17 is 1K + 20K. Does it mean that actual input impedance is 21K? Or is it 1K?

    I'm trying to figure it out to build relay attentuator. 10K vs 21K is huge difference for proper potentiometer selection.

     

  24. and now for something completely different part 3

    in Do It Yourself

    Posted

    Yeah, English is not my native language :)

    I'm going to use Toshiba 2SC5171/2SA1930 as output BJT. Pinout is same to MJE/MJF.

    Regarding matching, I'm trying to figure out what Ic or Ib or Ie I should aim at while matching them for CFA circuit.

    I've got different devices for measuring hfe. One of them declares measuring hfe @ Ic=5mA, others do this @ Ib=10uA, 1mA, 10mA. So I'm a little bit stuck here (Ic vs Ib, and appropriate range).

    mwl168  mentioned he's running 220mA bias current. Can it be asumed that 220mA is Ie? Maybe Kevin could chime in?

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