400 comes home, FULL CIRCLE......................

Discussion in 'Fisher' started by larryderouin, Feb 28, 2017.

  1. dcgillespie

    dcgillespie Fisher SA-100 Clone Subscriber

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    Way to go Larry -- I've recently been through much of the ground you're plowing now so not only does life go on (and it does), but it can remain great or get even better. Sounds like you've got it all under control. Congrats, and best wishes for all you're dealing with!

    Dave
     

     

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  2. buglegirl

    buglegirl I Want To Be The Girl With The Most Cake Subscriber

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    Larry,

    Ohhh a bigger console saver!!!

    Seriously. Was very glad to meet Christa when you stopped by a few months ago. You two are a perfect couple and congratulations!!!

    Frannie
     
  3. thornev

    thornev Well-Known Member

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    LARRY ! So now you have a bio-electronics device on which to work ! As you know, they require the MOST TLC. I wish you two all the best. Keep the Love and Communication flowing. Thorne
     
  4. Catmanboo

    Catmanboo AK Subscriber Subscriber

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    Cool beans, Larry! Glad something's going your way finally. You deserve it. Long may you 2 run! :hug::bigok:
     
  5. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    Thanks for all the Good wishes everyone. We told her parents yesterday, HooBoy! They're ok with it tho. I DID get THE LOOK from her Dad (all you guys know that look....) but it's all ok. I SURVIVED!!!


    Back to the 400. I installed 2-2200uf 50V caps in the BIAS Circuit, but may be having a Brain Fart. Nothing is soldered as of yet and before I do want to make sure it's right. The Negatives are tied together in the middle for the heaters and Bias, with the positives separate. On the diode Bridge I have the Positive lead connected to the 15ohmR and the right most Positive. And the Left most Positive is connected to the chassis ground on the Long T-Strip next to the cap clip. Negative side of the Bridge goes to the Negative side of the caps with the Heater and B- Leads? I can't find any of my old pics, and my other 400 is buried (in a box) at my storage unit. So I'm going strictly from Memory(and mine isn't the sharpest pencil in the box....) Would someone please Doublecheck me on this. Right now I'm gonna put a 10K pot inline for bias adjustment and later install a IBBA Board underneath when parts in my stash become available. I want to be able to fire it up for testing now, as it's been sitting on the bench or the truck for the last 23 months with me.

    Thanks
    Larry

    400 Bias Layout.jpg
     
  6. bhamham

    bhamham AK Subscriber Subscriber

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    You got it right, Larry!
     

     

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  7. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    Thanks Bruce.
     
  8. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    I figured out the WHY of the switch on the power cord. The switch on the volume control is FUBAR!!! (Ain't NO WAY I'm putting out 1&1/2 Ben Franklins for one!!) Gotta get into the storage unit and rummage thru the stash and see if I can come up with one). Disconnected the leads and soldered them together, 2 layers of heatshrink. Brought it up on a variac, and had a resistor (330ohm 3w R-43)that had grown a shorting bar to the ground lug on the T-Strip that I missed, go Chernobyl. And I was only up to 50V!! So I shut everything down, and pulled the offending shorting bar (actually a cap lead that had wedged in) and removed R-43. Completely OPEN. Ordered a few more along with some more CL-80's and a couple 27ohm 5W for the LK-72. I actually managed to outfit this 400 with All Sylvania Yellow label tubes for the IF/RF sections. Tele's in the preamps and phase inv., with GE's on the MPX, and Russkie EH 7868's. Oh DAMMIT! I forgot to order a couple 2x2 breadboards for IBAM/IBBA's. I'll make an order from AES tonight. In the meantime the 10K pot inline on the Bias B- will do for now.
     
  9. thornev

    thornev Well-Known Member

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    Larry - You do breadboards before installing a permanent circuit? Is that like your "design phase" where you see what component arrangement works best? Would you mind posting a pic of one because I've always had troubles with having to jumper over columns given the breadboard architecture underneath. Thorne
     
  10. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    I make the permanent circuit on the breadboard. When I do an IBBA I LITERALLY copy Dave's schematic to the board, and solder everything together. Same with the IBAM. I've never had to "jump over" anything. Any point that isn't used is scraped off so there is no connections where they ain't supposed to be. I'll see if I have any underneath pictures but I doubt it.
     
  11. thornev

    thornev Well-Known Member

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    I meant I'd like to see pictures of the circuit while still on the breadboard. And you mean you solder everything together while it's on the breadboard? How do you know it will fit in the chassis given all the other components around which you have to navigate?
     

     

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  12. fred soop

    fred soop Super Member

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    Control preamp boards for an ongoing rebuild / redesign. First is the actual breadboard and testing. Then the initial layout is done on graph paper, lightly, in pencil, with a BIG eraser. Then parts are test fit and adjustments made. Boards were also test fit before populating. There was actually a problem with improper gain in final test. Note in the last picture that there is a stray wire near the center of the board that did not get trimmed and was shorting.

    1701
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    Last edited: Jan 17, 2019
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  13. thornev

    thornev Well-Known Member

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    Thanks, fred soop. Those breadboards in 1701 look really complicated. How in the world do you go about planning all that out so it fits? What is the purpose of the graph paper? Do you have to start anew with it every time you do a redraw? and your final results are so incredibly neat. The underside traces too!! I know... practice makes perfect. I'm only 1 year in but really enjoying it. I'm always having to move everything around once I find out I don't have enough room on a side or I have to jump over 5 other components to get to ground for example. In my mind breadboarding would really improve my chances at success if I could make the circuit work on the breadboard.
     
  14. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    When I say breadboard, I'm using it for the finished boards that Fred shows. I take the circuit and build it to the schematic, usually on a 2" x 2" board. Then cut the excess off (if any). Self taught, so I'm not to the level of those who have E.E.'s or trade school sheepskins ;). It works but sometimes ain't pretty.

    As for fitment, I usually tuck it in a corner somewhere or on standoffs above the area it needs to be. The only long run is usually the B- lead. Everything else is as short as possible.
     
  15. fred soop

    fred soop Super Member

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    As for how to plan and the need for the graph paper (and the BIG eraser), the physical layout is drawn out with the points where the graph lines cross representing the holes in the perf board. Then parts are erased and moved such that the connecting wires underneath are close to straight and don't cross each other. The only need to start over and redraw is if there are major changes. This process is aided by the use of zero ohm resistors, the "resistors" with the single black stripe.

    One eventually learns that 1/4 watt resistors take 4 spaces and can be placed one space apart side by side. Film capacitors are the other extreme and create the need for a test fit of the actual parts. I also attempt to keep external connections on one edge of the board to allow for flipping the board up without disconnecting. The boards above do have additional connections on the right edge (power and dirty ground). The external leads to those will be routed and looped at the top so they will roll out without disconnecting.

    As for the complicated looking breadboards, it actually looks more complicated than it really is due to all of the interconnecting wires. What you see in the first picture is essentially one channel of a complete control preamp, including active filters, active loudness, tone control, etc. Note that if you look along the center groove of the breadboards, you will see only one IC. Also, component leads are not cut so everything is sticking up quite a bit.

    I've been doing this sort of thing since around 1967, so techniques have improved over that time.
     
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