Drake L4-B Resto

Discussion in 'Amateur Radio Amplifiers' started by WB1E, Sep 27, 2017.

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  1. WB1E

    WB1E Ham Member QRZ Page

    What I have here is 240v coming in from the PS, going to the ON/OFF switch. It is tied into the SSB/CW (2PDT) and comes back to the PS on 2 wires for each of those 2 modes. It does also power the filament xmf for the fan & RY-1 supply. The 12Vdc PS I am going to use goes from 100V to 240V so as described above, Actually I was going to tap off the fan supply as my delay cube takes 115V so still deciding where to tap in. One phase to the chassis is where I'm at in the PS currently.
    Last edited: Nov 20, 2017
  2. W1QJ

    W1QJ Ham Member QRZ Page

    One phase to chassis is a no-no. You can go across both phases with a hi power resistor to drop the other phase down and that will eliminate the shock hazard on the chassis if you lose the green leg. Why don't you put the step start relay up in the RF deck? This way you can get the proper 120vac off the CT of the primary of the filament transformer? Better practice. I rebuilt a Drake power supply using an SB-220 transformer and I wanted to make sure it mimicked an original PS so that it could be used with any Drake RF deck. Not a good idea to alienate the PS from the deck of vice versa. Unfortunately if you keep CW/SSB switch to change from hi/lo voltage, there still is a surge that can ruin that switch when going from cw to ssb. Best to modify the deck to stay with the high voltage all the time and use the cw ssb switch to change the bias point using a string of 1N5408 didoes and picking off your bias point with that switch.
    WB1E likes this.
  3. WA7PRC

    WA7PRC Ham Member QRZ Page

    Along my redrawing of the OE Drake schematics, that's in the drawings on my website. I'm still waiting to hear from you or @WB2WIK as to whether I drew it correctly.
  4. WB1E

    WB1E Ham Member QRZ Page

    Originally The filament xmf 115 CT point was where I was going to hook up the delay relay, and after tossing it around that is where I'll hook up. Thanks guys. This will work if and when & if the input voltage gets changed down the road. Now to start the mechanical installation part....Last weekend didn't offer me much time, perhaps this weekend.

    Looks like Mouser & CTS have found a 100k push-pull part number that their willing to quote price and availability with. More on that when I have something firm from them.

    Hope everyone had an awesome Thanksgiving.

    W9GB likes this.
  5. WA2LXB

    WA2LXB XML Subscriber QRZ Page

    Last edited: Dec 11, 2017
  6. W1QJ

    W1QJ Ham Member QRZ Page

    Hugh, newer electrolytic aren’t made like the old ones so to make a new one look like an old one you have to be creative. New ones are typically smaller for the same value. The thing to do is to dissect the old capacitor from one side by carefully cutting the opening around the end. Carefully scoop out the innerds of the old cap and put the new cap inside the old shell. Have the new leads coming out and then glue the piece you remove on one side back in place. Viola you gave a new cap with the old body style exactly. This is an old trick.
  7. WA2LXB

    WA2LXB XML Subscriber QRZ Page

    Hi Louis. Thanks for taking care of AH2O's 922 amp a few weeks back. Glad you're local!

    I'm not too particular about originality, I'm just lazy and want a neat install with a new capacitor that has long enough lead lengths so I don't junk things up extending leads. I plan to install a new 100 volt 100 microfarad polarized electrolytic. Unless I'm missing something about the old Cornell Dublier, I think that should do it.
  8. W1QJ

    W1QJ Ham Member QRZ Page

    What did I do to his 922?
  9. WA2LXB

    WA2LXB XML Subscriber QRZ Page

    He brought it over to you to make sure it checked out ok after 30 years in storage. You installed a soft key, checked tubes, blew out the dust... and that was it. Back around the middle of October. Since then he's put it to good use!
  10. W9GB

    W9GB Ham Member QRZ Page

    50+ years later, Cornell Dublier (CDE) bought out Mallory (Indianapolis) in 1980s and
    Illinois Capacitor (north suburbs Chicago) a few years ago.
    ** New Capacitor will be significantly Smaller. WHY? PLASTICS (The Graduate, 1967).**
    21st Century Material Science moved beyond cardboard and beeswax of that post-WW2 era.

    CDE Axial Lead Electrolytic Capacitors
    BR-series (BR 100-50) is now the WBR series (85°). NLW-series is Computer Grade (105°).
    From Illinois Capacitor the TMA (105°) and TTA (85°) series are now available from CDE.


    CDE Capacitors are available for purchase from the major
    USA Electronics Distributors (Allied, Digi-Key, Mouser, Newark).
    Last edited: Dec 11, 2017
    WA2LXB and WA7PRC like this.

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