1956 Hoffman Colorcaster (56K Warning - Lots of Photos)

[benman94]

Found yet another problem: someone at some point replaced components (I can't tell if this was recently or back during the set's service life) in the HV cage and did a piss poor job soldering. If I even look at the HV adjustment pot wrong I get bad arcing across a terminal strip in the bottom of the cage. The fly, thank God, wasn't damaged in all of this. I guess I'll sort out the mess in the HV cage first and move on from there.

[ohohyodafarted]

Hi Ben,

On a couple of occasions I have, added a tap to a regular control. In both cases I used a 4 watt clarostat wire wound control. The procedure is a bit of a pain but it can be done.

First remove the wiper and control shaft from the body. Then I grind off the 2 rivets that hold the wire element and end terminals into the bakelite body. Now you can remove the entire resistance element. Then using a Dremel I make a slot in the bakelite body where the new center tap terminal is to be located.. I make a new terminal of brass shim stock about 1/4" wide and 1" long and slide it through the slot I made in the bakelite body. Then I re-install the wire wound element into the body in such a way that the brass shim stock is wedged tightly between the outside of the wirewound element and the inside wall of the bakelite body, thus making a tight mechanical/eelectrical connection. Then re-assemble the original terminals at either end of the wire wound element replacing the old rivets with tiny brass screws, nuts and washers. Re-install thee wiper and shaft, and you're in business.

You will need a pot like this one to do the conversion.

http://www.ebay.com/itm/CLAROSTAT-50...3D232072262896

[ohohyodafarted]

Ben,
I see the pot just sold. Did you buy it?

[benman94]

That was infact me Bob.

[ohohyodafarted]

If you need any additional guidance making the mod, I will be glad to assist with what ever information I can provide. Good Luck. I know this will work, because it worked very well for me. A lot will depend on the skill of your craftsmanship. But with the right tools and materials, it is easily done.

One tip, if the brass shim stock fits to loose between the bakelite body and the resistance element, make the brass strip longer and double the thickness where it makes contact with the resistance element. Or possibly use thicker shim stock. The idea is to get a nice snug/tight fit so the shim stock makes good contact.

[Phil Nelson]

Hey, if you try the add-a-tap trick, how about taking a couple of photos? I have a set with a tapped 10-ohm WW pot that needs help, and a pic is worth 1,000 worlds.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[ohohyodafarted]

Originally Posted by Phil Nelson

Hey, if you try the add-a-tap trick, how about taking a couple of photos? I have a set with a tapped 10-ohm WW pot that needs help, and a pic is worth 1,000 worlds.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

When I do the mod for Ben, I will document the procedure with a How To page on my website and place a link on this thread.

[ohohyodafarted]

Originally Posted by Phil Nelson

Hey, if you try the add-a-tap trick, how about taking a couple of photos? I have a set with a tapped 10-ohm WW pot that needs help, and a pic is worth 1,000 worlds.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

I just finished doing this center tap mod on a 10 ohm 4 watt Clarostat pot for Phil Nelson. I have documented the procedure and posted instructions and photos at my web site under the "My Methods" section. It's the bottom entry "Pot Center Tap Mod"

Link to my web site is at the bottom of this post.