----- Original Message ----- From: "Alan" ve4yz@mts.net To: "'George Burr'" gaburr@magma.ca; amsat-bb@amsat.org Sent: Tuesday, September 16, 2008 4:16 AM Subject: [amsat-bb] Re: replacement pots

In about 2 weeks I'll have an AZ and EL on the bench and check

measurements.

All the bolts on my Yaesu/Kenpro 5400 rotators are metric so the shaft on the pot may also be metric.

We will see.

-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of George Burr Sent: September 15, 2008 9:03 PM To: amsat-bb@amsat.org Subject: [amsat-bb] replacement pots

I found the pots on the old Kenpro rotors to be none standard. The mounting hole and the turning shaft are smaller than standard and this could require some more work to fit a "standard " pot because of the gearing. I don't know if this is true for the G5400. 73 Geo. Amsat# 26245

Hi Alan, Geo, and All

I have in my hands an original 500 ohm wirewound linear potentiometer as a spare part for my Kenpro's rotor family and all dimension are metric as follows:

Outside diameter: 28 mm Outside thickness: 15 mm Metal shaft diameter: 6 mm Metal shaft lenght: 24 mm Bushing outside diameter: 9 mm Bushing lenght: 10 mm

Remember that 1" is equivalent to 25.4 mm

The above original potentiometer is custom made and do not carry on the name of it's manufacturer. The power rating of it is in the order of 2 watt and it is a 360° continuous rotation potentiometer using a looped flexible centre wire for the wiper.

By the way I found in internet a Model 5311 single turn wirewound linear precision potentiometer made by STATE Electronics that can be adapted to replace the original one with two minor mechanical changes.

The above potentiometer is available with standard resistance of 500 ohm and a total mechanical travel of 360° for continuous models with independent linearity of +/- 0.5% and power rating of 2 watt

http://www.potentiometers.com/Series5311.cfm?session_num=2008091501464

http://www.potentiometers.com/pdf/BITC_5311.pdf

The outside diameter of it is 1.312" = 33.33 mm and apparently it can be accepted into the gear mount plate of the KR-500 rotator but if a rotator is available open for maintenance the available room for the new diameter of 33.33 mm versus the original one of 28 mm must be checked.

The bushing outside diameter is 3/8" or 10.3 mm so that "probably" the original hole onto the gear mount plate must be enlarged boring it by only 1.3 mm

The diameter of the metal shaft is 1/4" or 6.342 mm so that the inner diameter of the pot devider gear must be enlarged boring it by only 0.342 mm

The above precision potentiometer is much better than the original one because it is totally incapsulated and the mechanical continuous travel of 360° is made without using a looped flexible center wire for the wiper

The original 500 ohm potentiometer from Kempro is very difficult to find in Italy and if available the cost of it is about 50,00 Euro.

I hope this helps.

73" de

i8CVS Domenico