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Author Topic: Drake L-7 10 Meter Mods  (Read 569 times)
KF5U
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« on: March 03, 2005, 06:47:52 AM »

I posted this question in the "Amplifiers" forum several days ago, but so far I haven't received any responses.

I am making the 10 meter adaptation to my Drake L-7 per the instructions given in the QST article back in the 1980's. I have made all the modifications except the one where you connect a 68 pf capacitor to the input side of the 15 meter coil. (The input side is the bottom end closest to the clip).

I have yet to figure out just how to get to the bottom of the 15 meter coil to solder in this capacitor. It seems impossible to reach down that far through the removeable cover on the bottom to access the lower part of the 15 meter coil.

If any of you have completed this modification, I would most appreciate hearing how you accomplished it.

Thanks and 73,
J D Lambright - KF5U
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KL0S
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« Reply #1 on: March 04, 2005, 04:35:17 AM »

JD - I did my L7 here recently and had exactly the same question. If you're lucky like I was you'll find that those additional capacitors are already installed!!!  Look inside the box that contains the input coils and count the number of silver micas in there -- if you look at the schematic you'll see 8 caps for the domestic version and then the two export model caps marked in dotted lines.  Add them all up and you get a total of 10 -- if there are 10 inside the box then you should be ok (and if you look carefully you can see the connections in the correct orientation for those two caps).  If not bless your heart if you can do it....as I was getting help from the Drake reflector one guy told me he was able to install those caps with "...a couple of hemostats and LOTS of bad words!"

The other part of the mod is MUCH easier, just bypassing the high-pass filter...be careful to follow the instructions.  Doing that is a lot easier than replacing the entire run of coax.

Hope you're lucky like I was.

GL - Dino KL0S/4
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KF5U
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« Reply #2 on: March 04, 2005, 08:20:08 AM »

Dino (KL0S/4),

Thanks for the info. Looks like you've experienced the same problem. I actually have two Drake L-7's, both in beautiful condition. One had the capacitors added when I got it, but the other one doesn't. I've made the other required mods, but getting that last capacitor soldered in place seems nearly impossible - even with having a go-by to look at! I just don't see how you can get down next to the chassis that far to get to the lug on the 15 m coil. The QST write-up makes it sound so easy. Maybe I can't see the forest for the trees!

Thanks and 73
J D Lambright - KF5U
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