Thinking about building the Keppinger .....

Posted: 2/15/2011 5:16:39 PM
mraroid

From: Portland Oregon

Joined: 2/15/2011

Hi...

I have thought about building a vacuum tube powered Theremin for a while. I am looking at the Keppinger schematic labeled Rev 7, 12/20/08. Is this the latest, or have folks made some mods since then?

I am not a electronic whiz, but I can find my way around old vacuum tube radios. I can do simple things like find bad caps, measure resistors and I have a nice working tube tester. I can solder OK.

Is any other documentation around for the Keppinger design? (I have the parts list). I would enjoy seeing some photographs under the tube chassis. I have read about buying or making coils, and i have seen the site that has some for sale for $200. I am thinking about winding my own, but don't want to do a sewing machine mod to do it. Is it possible to hand wind and have it still come out looking nice (and work)? How about blank (with cut outs)tube and power supply chassis? Is anyone set up to make some? I thought I might see some on ebay.

Any tips, traps, or advice appreciated. I try to do my homework, but I need some examples to go from.

Thanks
jack
Portland Oregon

Posted: 2/16/2011 8:59:47 AM
Chobbs

From: Brooklyn,NY

Joined: 12/1/2009

You probably saw my site with the kep coils...
It may seem counter intuitive, but I would recommend NOT using a motor to wind the coils...its a mess, and really not worth it. I do it all by hand- Tedious... but you will have better control, neater and tighter winds, and less of a headache. Make a hand-crank winder like in Marks coil making video. The important part is having a counter mechinism to keep track of the # of turns.
Phillip N.'s probably has the best kep build site...(I forget the link but you can find it)
and he has a few chassis pics. levnet member, Dan Schrieber was making pre drilled chassies last summer for a very reasonable price.... maybe
he still has some. They were on ebay, so Id check there first.
I have the chassis drawings posted on my site, if you need to make your own.

There is also a great Keppinger theremin yahoo group, but I can never find it.
Posted: 2/16/2011 6:36:47 PM
shobley

From: USA

Joined: 8/25/2009

I would heartily recommend it!

The hardest thing was winding the coils - and diagnosing the fact that I'd hooked one coil up backwards without realising it.

Fortunately the good people on this forum were a big help.
Posted: 2/16/2011 6:54:56 PM
mraroid

From: Portland Oregon

Joined: 2/15/2011

Hi... Thanks for your post. I have subscribed to the yahoo web site, but have not yet been OK'ed by the moderator.

I may toss in the towel and buy your coils. However I just found this site:

http://hamwaves.com/antennas/inductance.html

which looks very interesting to any one who wanted to wind your own coils. Even so, I could save so much time if I bought coils and the two chassis. I must admit, it is a pride thing if my made my own coils.

I do have a couple of questions:

1) Unless I missed it, I could not find the values of L1-L6. Can some one post them?

2)I know short wire runs are the best. When I look at photos of the underside, I see different wire gauges and some shielded(?) wire. Has any one written or posted information on this? Any tips?

I am still in the reading stage. I am searching for web links, photographs and such. I am for now sold on the Keppinger build. I like vacuum tube stuff anyway.

Thanks for the tips.

jack


Posted: 2/17/2011 11:23:18 PM
Jeff S

From: N.E. Ohio

Joined: 2/14/2005

"Unless I missed it, I could not find the values of L1-L6. Can some one post them?" - mraroid

No, you didn't miss it. There's no "value" listed for the air coils. You have been given complete dimensional and winding information.

You are free to calculate a value if you feel you need to have it. The problenm is that it will still only be an educated estimate. As you probably know, the actual value will depend on the actual turn count, winding density and final coil length. That's assuming the winding form is the correct diameter and the wire/insulation the proper size.

You may find this (http://www.daycounter.com/Calculators/Air-Core-Inductor-Calculator.phtml) helpful.

You must be logged in to post a reply. Please log in or register for a new account.