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Author Topic: Drake L7 Load control is slipping  (Read 5825 times)
K9RJ
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Posts: 33




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« on: August 02, 2012, 08:47:28 PM »

The Drake Load control has a reduction drive and mine is slipping.
Can anyone tell me how to fix this. Access looks like a challenge.
Thanks
Harris K9RJ
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W1QJ
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Posts: 1447




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« Reply #1 on: August 03, 2012, 03:45:11 AM »

A  reduction drive can only take so much tension on it.  It there is too much it will stop.  Make sure nothing is binding.  I there is no binding it may be stripped or gummed up.  Remove it and clean it and re grease it.  If it is stripped you will need to replace it.  Ameritron units might work as a retrofit.
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K9RJ
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« Reply #2 on: August 03, 2012, 07:09:07 AM »

Lou, Thanks for the response. Do you have any information on how to get the reduction drive out? I tried to take the front panel off last night but there is an issue with the wiring harness behind the front panel switches. It looks like I would have to unsolder every single wire going to the little circuit board behind the the 6 switches. I have been looking for a Drake L7 service manual that might explain how best to do this but there does not appear to be one.
Harris K9RJ
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W1QJ
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« Reply #3 on: August 03, 2012, 10:00:04 AM »

Hi Harris, I just got my first L7 a couple monmths ago.  They are actually a pretty rare amp.  I don't get them in for repair much nor L4B's either.  They are good amps.  So I never took a front panel off.  I'll have a look at mine and see.  I'll try to help if I can. Lou
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K4DPK
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« Reply #4 on: August 03, 2012, 09:36:18 PM »

I believe those are Jackson planetary drives.  If so, they are friction ball drives that run in a race, so they can't actually "strip".

The first thing to make sure of, tighten the setscrews to make sure the shaft isn't slipping in the drive or associated couplings.  Then, once you are sure it's the drive that is slipping, you can use a pair of duck-bill pliers to gently squeeze the tabs that hold the two shell-halves together.  That will increase the friction between the balls and the race, necessary for a positive drive.

Phil C. Sr.
k4dpk
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K9RJ
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Posts: 33




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« Reply #5 on: August 03, 2012, 10:26:37 PM »

Thanks for the tips. I am examining how to remove or at least move the front panel enough that I can get a shot at the drive.
Harris K9RJ
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K9RJ
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Posts: 33




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« Reply #6 on: August 04, 2012, 10:07:55 AM »

To those who are following this saga, I have moved the two meters out of the way and have almost got to the planetary drive by loosening the panel. I have not yet unscrewed the circuit board holding all the switches because I would have to deal with the SSB light and I am having trouble getting it out of the white holder.
More to come ...
Harris K9RJ
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WA7KGX
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« Reply #7 on: August 04, 2012, 12:52:17 PM »

On my L7, the Plate control is on a drive but the load is not.

If you can move the control at all, perhaps a bit of unfreeze goo will free it up.
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K9RJ
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Posts: 33




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« Reply #8 on: August 04, 2012, 03:57:19 PM »

Planetary drive is now out. It is marked JB (which I assume is Jackson Bros.) and also Made in England. I have emailed the supplier with several photos of the drive to see if they have a replacement.
Harris K9RJ
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K4DPK
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« Reply #9 on: August 04, 2012, 05:10:03 PM »

Did you try pinching the tabs to bring the shell halves closer together and increase the contact with the balls inside?

Phil C. Sr.
k4dpk
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K9RJ
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« Reply #10 on: August 04, 2012, 09:20:08 PM »

Phil, When I removed the planetary drive the shaft was already binding so squeezing it tighter would not help. I suspect that the balls have been damaged. I am now looking for a replacement.
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G3RZP
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« Reply #11 on: August 05, 2012, 12:51:10 AM »

I have found that washing them out with a grease solvent some times works. Then dissolve some new grease - you don't need much in a solvent that evaporates and soak the drive in it so the new grease gets carried inside and then leave it to dry.

Although the 4511 drive (that's the Jackson Bros part number) is still made, there are several variations of it concerning flanges for attaching a dial, so it is necessary to know exactly which variety you need. That design dates back to the 1930s, by the way. The earliest equipment I've seen with it was in the R1116 receiver, used by the Fleet Air Arm Swordfish biplanes and introduced in 1936!
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K4DPK
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« Reply #12 on: August 05, 2012, 07:21:04 AM »

As Pete suggested, cleaning it out is a good next step.  Just carefully lift the tabs (no more than absolutely necessary) enough to pull the shell halves apart, so you can get to the innards.  If the ball bearings are rusted, clean them with steel wool.

The grease inside has probably solidified.  Cleaning and re-greasing is in order.

Phil C. Sr.
k4dpk
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N0WOP
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« Reply #13 on: August 05, 2012, 09:33:11 AM »

http://midnightscience.com/catalog5.html#part4B

My l4b drive failed and I messed with it for days.  In the end, someone put me on to this website and part number.

I believe the shaft is a bit longer than original, but I'm sure you could cut it down if you want.

And it was on my plate control, not the load on my l4b.

thanks
Joe
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K9UX
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Posts: 1




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« Reply #14 on: August 09, 2012, 10:56:02 AM »

Harris, My name is Dave, K9UX. I have bought several items from Jim Jorgensen's estate.
Fomerly known as K9RJ.
I have a Drake L-7 that Jim bought in Utah a number of years ago. It did not have the
power supply with it. He designed and built a power supply to go with it. It is very well built
and as you know, he was quite a builder.
I am looking to sell this amp and wanted to know if you would be interested in it.
Contact me off list at k9ux@mchsi.com.
I appologize to the other guys on the list as this was the only way I could get in touch with Harris.

73's Dave K9UX
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