{"id":1213,"date":"2018-09-22T19:46:04","date_gmt":"2018-09-23T02:46:04","guid":{"rendered":"http:\/\/philcoradio.com\/library\/?page_id=1213"},"modified":"2018-09-25T21:12:12","modified_gmt":"2018-09-26T04:12:12","slug":"re-creating-dogbone-resistors","status":"publish","type":"page","link":"https:\/\/philcoradio.com\/library\/index.php\/shop-talk\/techniques\/re-creating-dogbone-resistors\/","title":{"rendered":"Re-creating “Dogbone” Resistors"},"content":{"rendered":"

[Contributed by Steve Davis]<\/strong><\/em><\/p>\n

I want to apologize for some of the out of focus close-ups. I have two cameras, neither will focus on a close object.\u00a0 \u00a0-Steve<\/span><\/strong><\/p>\n

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A\u00a0while ago there was a thread on the restoration of a model 18. The poster mentioned how colorful the underside of the chassis was with all original “dogbone” resistors and what a shame it is to have to replace many of them. I posted a picture of a dogbone that I had made. I have decided to to post a tutorial on how to do it.<\/p>\n

For this tutorial, I’m going to make a 240K 1watt dogbone resistor.<\/p>\n

To start off with, we need a piece of plastic tubing about 1\/4 to 5\/16 inch in diameter, it needs to be cheep and readily available. I found a ballpoint pen that was perfect.<\/p>\n

\"[Image:<\/div>\n

by\u00a0Steve Davis<\/a>, on Flickr<\/p>\n

I cut the tubing to length, about 1 inch for a 1\/2 watt or about 1-3\/4 inch for a 1 watt, as in this case. I chuck the pen in the drill press, bring the table up until it just touches the pen. Then cut the tubing using a razor blade attached to a block of wood. This produces resistor bodies of uniform length.<\/p>\n

\"[Image:<\/div>\n

by\u00a0Steve Davis<\/a>, on Flickr<\/p>\n

Now, cut a small notch in each end to bring the leads out.<\/p>\n

\"[Image:<\/div>\n

by\u00a0Steve Davis<\/a>, on Flickr<\/p>\n

This is a tool made from an X-acto knife to twist the resistor leads. The prongs were made by heating and bending a\u00a0large sewing needle into a “J” shape and inserting it into the slot of an X-acto knife handle.<\/p>\n

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<\/div>\n

\"[Image:<\/div>\n

by\u00a0Steve Davis<\/a>, on Flickr<\/p>\n

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<\/div>\n

\"[Image:<\/div>\n

by\u00a0Steve Davis<\/a>, on Flickr<\/div>\n

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\"[Image:<\/div>\n

by\u00a0Steve Davis<\/a>, on Flickr<\/p>\n

I soldered two 120K ohm 1\/2 watt resisters together in series. Then, using 18 ga. buss wire, I extended the leads. I use 6 inches of wire,\u00a0this gives about a 3-1\/2 lead length when finished.<\/p><\/div>\n

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\"[Image:<\/div>\n

by\u00a0Steve Davis<\/a>, on Flickr<\/p>\n

I have now inserted the resistors into the tube and brought the leads out through the notches.<\/p><\/div>\n

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\"[Image:<\/div>\n

by\u00a0Steve Davis<\/a>, on Flickr<\/p>\n

Using “JB Quick” or “Locktite Weld” (JB Weld is to slow for this job) completely fill the tube. Use your finger to pack the epoxy into one end until it comes out the other. The theory here is, the epoxy will transfer the heat to the outer surface.<\/p><\/div>\n

<\/div>\n
\n
\"[Image:<\/div>\n

by\u00a0Steve Davis<\/a>, on Flickr<\/p>\n

Now wrap each lead around the tube two times. I started near the end and wrapped toward the middle.<\/p><\/div>\n

<\/div>\n<\/div>\n<\/div>\n
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\"[Image:<\/div>\n

by\u00a0Steve Davis<\/a>, on Flickr<\/p>\n

Solder the wraps<\/p><\/div>\n

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\"[Image:<\/div>\n

by\u00a0Steve Davis<\/a>, on Flickr<\/p>\n

The resistor is now ready to paint. Dip the resistor and sling the excess.<\/p><\/div>\n

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\"[Image:<\/div>\n

by\u00a0Steve Davis<\/a>, on Flickr<\/p>\n

<\/div>\n
\"[Image:<\/div>\n

by\u00a0Steve Davis<\/a>, on Flickr<\/p>\n

After the body has dried, dip the end and add the dot with a small brush.<\/p><\/div>\n

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\"[Image:<\/div>\n

by\u00a0Steve Davis<\/a>, on Flickr<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

[Contributed by Steve Davis] I want to apologize for some of the out of focus close-ups. I have two cameras, neither will focus on a close object.\u00a0 \u00a0-Steve A\u00a0while ago there was a thread on the restoration of a model 18. The poster mentioned how colorful the underside of the chassis was with all original […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1317,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1213","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/pages\/1213","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/comments?post=1213"}],"version-history":[{"count":0,"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/pages\/1213\/revisions"}],"up":[{"embeddable":true,"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/pages\/1317"}],"wp:attachment":[{"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/media?parent=1213"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}