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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

    Lou,

    Thanks for the comment, yea she's hurt'in right now, still new and not yet loved.

    It looks great, I even painted the cover rubbed oil bronze (she's a brown one). But finally hooking it up between my feedline and the Bird System Analyzer, anything above 300 watts makes it sing, or perhaps better described "hissing sound". The "bypass-coax1-longwire-coax2 rotary switch knob and behind the front panel, the square grey 4 position sequencer? was moving around loose.

    The only way I can get any "tune ability" (tune-a-billy here in certain parts of Texas) is to have it in the "Bypass" position. However I'm connected going into the "Input" So-239 and going out on Coax-1. and after all that, it reads SWR correctly, watt Meter ok, just fails the dielectric test making a hissing noise above 300 watts.

    It is a damn good tuner as you have stated, and I look forward to having my way with it soon! As the Murch has served me well (hamfest deal at $30) but is not built to the same standards at the SA 2060a Heathkit.
     
  2. WA2LXB

    WA2LXB XML Subscriber QRZ Page

    I am currently rebuilding the roller inductor assembly on my 2060 (no "A"). I plan to replace the Drake MN-2000 with it. The silver plating is worn off the inductor for about half its length, so I plan on flipping it. I've heard of some hams experiencing arcing on the 2060 series, between the internal balun and the variable cap right next to it...or to the adjacent silver plated straps. If this is happening, push things away from the balun and consider using some heavy electric tape, such as 3M-130C, to insulate the arcing spots. Hopefully you're not seeing arcing in the capacitor plates.
     
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  3. WB1E

    WB1E Ham Member QRZ Page

    I guess I'll have to close the door and turn off the lights. :) Reminds me of...oh never mind :) just need to keep the cat out.

    Hugh, that's a great idea actually. Mine is in the same shape around #75. I was going to attempt or at least investigate re-plating it. The roller itself may need some work also. I need to get some 1/4" brass rod and spin up a new roller on my little 8x19 lathe.

    Where does one go to discuss their Heathkit tuner woes? In the Boat Anchor threads?

    Hope to hear you Hugh someday on that contraption Hi! Like me, I still have nice black silver oxide on the coils :(

    Can't wait to run my Swan through it on the Boat Anchor's Net (3870) and say I got some new finals.

    Doug
    N5DMC
     
  4. W1QJ

    W1QJ Ham Member QRZ Page

    NEVER had a bit of trouble with my 2060a never hissed or arced a single time. I pre-tune it perfectly using my MFJ-259 then switch over to the radio and touch it up (it changes a tiny bit) then after the radio I hit it with the big power from the amp. Once again a quick tweak and I'm good. I suppose once they start arcing and you get a trace going you'll have problems a lot easier and faster. If try putting mucho power into it and then trying to tune it I can see it arcing. If you have an MFJ 259 stick it on a coax switch and use it to pre tune and you will never arc it.
     
  5. WA2LXB

    WA2LXB XML Subscriber QRZ Page

    For Heathkit parts try Ron Oxley... http://www.rtoham.com/products/parts/ He often has parts that he doesn't advertise on his parts web page.

    I have a spare port on my antenna switch to use my analyzer on the tuner like Lou does. Haven't needed it with the MN-2000, but I'll probably use it for the roller on the 2060 until I get all the bands/settings into a spreadsheet. I always tune with 20 to 30 watts max.

    The skin resistance of silver is much lower than tarnished copper, and I believe that silver oxide is lower than both silver and copper. I've looked into replating the inductor, but it's really next to impossible without taking the wire off the spool. At that point you're better off trying to find some silver plated or solid silver wire of the same diameter and rolling your own over the fiberglass core. I looked into the price of wire at one point and it was north of $200 for a dozen feet of solid silver...can't remember if I was able to find silver plated. RE the roller, you'll want to silver plate that after you've machined it. If you look carefully at the roller axle or rod, it is also silver plated...or was...check the very ends.

    BTW, I'm seeing 900W out CW to dummy, 1200W out SSB to the dummy. MN-2000 is also doing a fine job keeping SWR below 2.0

    Here's a little Drake porn for you:

    20180324_223310.jpg
     
    Last edited: Mar 27, 2018
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  6. WB1E

    WB1E Ham Member QRZ Page

    I enjoy a perfect match with less than 100 watts initially, so It will need a going through. It's brand new here in the shack.
     
  7. KG2DT

    KG2DT Premium Subscriber QRZ Page

    just picked up a mint l4b and added a whole bunch of features soft start, delays etc to it. For soft start I used a great board - in 240V out 240 time delayed 4 seconds via 4 x NTCs works great! a nice feature of this board is that it has a terminal block for a low voltage spst switch to turn the amp on/off. Install it in series between power in and power feed to the PS. Added a toggle switch in the PS and I now leave the on/off in the rf deck in the ON position so that switch will last a lifetime. An old issue wit l4b's - solved!. On/off is now via the toggle switch. I added also a voltage/current monitor to the front of the PS so you can monitor incoming V/I of the mains. Board cost is about 50 bucks on ebay worth every penny.Relays are rated to 30A block terminals are rated to 20A plenty juice to feed the l4b. If you want higher current replace the terminals by 30A ones or just solder the wires to it. IMG_20180329_125640779.jpg IMG_20180329_125640779.jpg
     
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  8. WA2LXB

    WA2LXB XML Subscriber QRZ Page

    Hi Alberto...would you please link to the eBay V/I PS monitor you chose? Thanks!

    I think I have the same soft start that you have...got it from a ham in France.

    BTW, I also added some 12VDC fans I had lying around to exhaust the top of the PS and powered them from the station power supply. I'm going to put a rheostat in line as they are a little noisy at 13.8VDC. If I had 24VDC fans that would have been better, but these were free :)
     
  9. KG2DT

    KG2DT Premium Subscriber QRZ Page

    of course Hugh. There are a zillion different models/colors - the works - so better than a link do an ebay search for (no apostrophes) "D85 digital meter" they are dirt cheap just make sure that the set you buy comes with the toroidal current pickup . When I got mine (bought a whole bunch) there were no blue 7 segments.... buying a few more now. Be patient it takes 2+ weeks to get them from China (EMS) but they do come in. On a secondary note if you need more precision than 99.9 amps (i.e 9.99 A) 5 minutes of surgery will do the trick. You need to electrically "move" the position of the decimal comma and wrap ten turns of the power feed on the toroidal so you get the x10 current multiplier. Alternatively you can tinker with the input voltage divider for the meters. Let me know if you have any ?
    73
     
  10. KG2DT

    KG2DT Premium Subscriber QRZ Page

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