Thursday, 14 December 2017

Kenpro overhaul (2)

In a previous post I wrote I would do some work on the Kenpro KR600 (not to be confused with the RC (Round Clock) model. Well, it took some time and effort to get everything ready. Besides that I discovered a few things I didn't find on the internet about this rotor. I found a excellent repair guidline for the KR400 by DL3LAR, he has some very good tips but doesn't tell you everything especially not when you forgot to mark everything. It also seems the KR400 doesn't have end-stop switches like the KR600. However the tip to set the potmeter in the center position and so set the clock to position North before you remount was a very good one.

First of all a cleaned everything including the bearing balls. The bearing shells were worn a little I solved that with a layer of 2 component "liquid steel".

The new potmeter unfortenately didn't fit well, had to do some metal filing. I had to file the hole which is circled red at the picture.

I my previous post I told there was no stop on the potmeter. When I received the new one there was a small paper enclosed to tell me the old potmeter didn't have a stop. Ah well, so that was not broken but the rest of it was not good either.

Another thing I discovered was the bearing shell / gear that fits over the first layer of balls. 4 sides are partly elevated and fit into the cover to connect it to the gear, first I thought all 4 had the same size, but when I mounted everything together I couldn't fit it straight. In the end it seemed one side has a larger elevated part (red circle). And of course that fits directly in the cover at just one place, which is the opposite of the end-stop activator inside the cover. If the rotor/potmeter is set at the center position this is the way the shell has to be mounted.

One of the end switches was not working well either, luckely with a bit of pressing and bending the switch arm it was quickly solved.

Of course everything was lubricated well with a thick layer of ball bearing grease. This way I hope the rotor will hold for years to come.

Well, in the end everything went well and the rotor is working fine again. It is a bit more complicated compared to the Create rotor I did before but at least as good I think.

Now, another thing I wanted to change. The metering scale of the controlbox is north oriented, that's fine if you live south of the equator or at least in other countries outside Europe. Probabely this is typical Japanese?

Credits G4DMF
So I was searching for a new scale as of course someone did this before. I found a reasonable one and printed it on photopaper with good enough results. When everything was ready of course I found another one in 600dpi GIF format, much sharper. But so far I'm satisfied with the result.
If you print this one you need to cut it in a photoshop program and print it measuring 8x7,2cm. The holes for the LEDs are not in the picture you need to figure it out yourself. Originally this scale was for the Kenpro KR400 which has probabely no LEDs for left/right turn indication.

When disassembling I noticed the lightbulb is a simple truck 24V dashboard light with Ba9s fitting. You can find several color LEDs for those on the internet. I had the idea to change the light match the green display of my Icom IC-706. But you can of course change it any colour you want. Don't forget the LED bulbs are DC and not AC, you need to add a diode to get a DC voltage on the LED.

Resulting in this:

Left: original light, right: New green LED light


  1. Hallo Bas, hij ziet er weer uit als nieuw en van binnen ook. Leuke klus. Die gaat weer jaren mee. Die van mij heb ik in 2007 onderhanden gehad. Doet het nog prima maar de potmeter geeft af en toe een hik. Tja, wat wil je 10 jaar en bijna dagelijks gebruik. Veel plezier ermee Bas. Ik hoop dat hij het weer jaren volhoud. 73 Hans, PE1BVQ.

    1. Potmeter is vrij makkelijk te vervangen Hans, dat zie je wel. Kost ongeveer 36 euro incl. verzenden. Is wat prijzig voor een 500 Ohm potmeter maar dan werkt het wel. 73, Bas

  2. It won't be too long before I attack my 600 version. It's really quite amazing how well these old Kenpro units operate and last in such severe conditions. Mine happily turns a 3.9m boom Yagi in 110km/h+ wind!

    1. Kenpro rotors are quite old if you ask me. But there are still many around. It has to be a good rotor. 73, Bas

  3. Hoi Bas, ja het vervangen is niet moeilijk. 10 jaar terug bij beide rotoren de potmeter vervangen. Potmeter is inderdaad duur vergeleken met andere potmeters. 470Ohm is voor een paar euro te koop maar die 500 Ohm is niet gangbaar dus betaal je daar de prijs voor.


Thanks for your comment. Bedankt voor je reactie. 73, Bas