I’m working on bringing an HP 8007B pulse generator back to life. One of the things I needed to fix is the snapped off paddle to the output attenuator. The switches on this and other HP products from this era, uses a custom scheme where the switch is integral to the PC assembly and the switch contacts are on the PC board. A plastic assembly that contains a slider with switch fingers, spring for detents, and a switch paddle fits between two plastic rails or guides. The guides for the slider is riveted to the board. This page provides the details on creating and 3D printing a replacement paddle. Tam Hana and Wilko Bulte were instrumental in helping make this a successful repair. Wilco provided a sample paddle from which I was able to make accurate measurements needed to create a 3D model suitable for printing. Tam provided help and guidance on using OpenSCAD to create the model. I also used Tam’s very excellent book "Technical Modeling with OpenSCAD" as a resource.
The printer used, a Creality Ender 3, was not very exotic or high end so I was skeptical that it would have a high enough resolution to print such a small part. It turns out the Creality printer was able to make a part that was more than suitable. Here is some of the details about printing the 3D part:
The finished printed part did require a small ammount of re-work using small files and an X-Acto knife. When the first layer is printed the notch for the spring tended to close up slightly. Cleaning the notch with the knife and files fixed the problem. On the completion of the repair the newly created part works perfectly and can barely be distinguished from an original lever.
Photo of Switch Lever
Rendered in Open SCAD
Photo compared to Meshlab Render
Dimensioned Drawing
3D rendering of STL File Using JSC3d
//
//Switch lever used on HP equipment.
//
/*
Changes from hp_lever-2.2.scad to hp_lever-2.4.scad
Increased size of notched cube by .6mm in x (50 to 56)
Translated notched cube -.4mm in x (33 to 29)
Translated notch cylinder -.3mm in x (57,5 to 54.5)
Translated notch cube -.3mm in x (50 to 47)
Decreased size of main body cube by .3mm (50 to 47)
Increased size of spring notch by .05mm (7 to 7.5, 3 cubes)
Changed SVG lever_06.svg to lever_07.svg (improved curve)
*/
// Set Viewport
$vpr = [55, 0, 323];
$vpt = [10, 4, -2.5];
$vpd = 70;
//Scale by 1/10
scale([.1,.1,.1]){
//Merge geormetries
union(){
//Import and extrude SVG geometry for lever
translate([82, -25, 15]){
linear_extrude(height = 30, center = true, scale=1) {
import(file = "lever_07.svg", center = false, dpi = 96);
}
}
//Notched cube
difference(){
translate([29, -25, 0]){
cube([56,50,70]);
}
rotate([90,0,0]){
translate([54.5, 35, -26]){
cylinder(52,7.5,7.5, $fn=100);
}
}
translate([47, -26, -1]){
cube([15,52,35]);
}
}
///////////////-Subtracted Geometries-///////////////
//Main body and spring holder
difference(){
translate([0, -95, 0]){
cube([47,190,30]);
}
translate([11, -96, -1]){
cube([7.5,36,32]);
}
translate([11, 61, -1]){
cube([7.5,36,32]);
}
translate([11, -95, -.1]){
cube([7.5,190,15 ]);
}
translate([-3, -23, -1]){
cube([8.5,46,32]);
}
//End Notchs
translate([-.5,80,-1]){
cylinder(r1=5, r2=5, h=32, center=false, $fn=100);
}
translate([0,-80,-1]){
cylinder(r1=5, r2=5, h=32, center=false, $fn=100);
}
}
/////////////-End Subtracted Geometries-/////////////
//Mounting tabs
translate([-13, (35.5+11.85), 9.75]){
cube([26.5,23.7,19.5], center=true);
}
translate([-13, -1*(35.5+11.85), 9.75]){
cube([26.5,23.7,19.5], center=true);
}
//Center Support
translate([9, -4.5, 0]){
cube([26,9,30]);
}
}
}
Open SCAD Code
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!-- Created with Inkscape (http://www.inkscape.org/) -->
<svg
width="210mm"
height="297mm"
viewBox="0 0 210 297"
version="1.1"
id="svg12"
inkscape:version="1.1 (c4e8f9e, 2021-05-24)"
sodipodi:docname="lever_05.svg"
xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
xmlns="http://www.w3.org/2000/svg"
xmlns:svg="http://www.w3.org/2000/svg">
<sodipodi:namedview
id="namedview14"
pagecolor="#ffffff"
bordercolor="#666666"
borderopacity="1.0"
inkscape:pageshadow="2"
inkscape:pageopacity="0.0"
inkscape:pagecheckerboard="0"
inkscape:document-units="mm"
showgrid="false"
showguides="false"
inkscape:zoom="3.3602084"
inkscape:cx="170.07874"
inkscape:cy="1075.8261"
inkscape:window-width="1312"
inkscape:window-height="936"
inkscape:window-x="62"
inkscape:window-y="29"
inkscape:window-maximized="0"
inkscape:current-layer="layer1" />
<defs
id="defs9" />
<g
inkscape:label="Layer 1"
inkscape:groupmode="layer"
id="layer1">
<path
fill="#f8da2d"
d="M 25.00236,297.04 H 0 v -50 h 25.00236
c 0,0 11.685749,4.95901 32.498645,9.97199
20.812893,5.01298 32.498993,5.02816 32.498993,5.02816
v 20.00077 c 0,0 -12.15564,0.43744 -32.498993,5.0278
C 37.157649,291.65907 25.00236,297.04 25.00236,297.04 Z"
id="path73"
style="stroke-width:0.352773" />
</g>
</svg>
Inkscape SVG XML
Freshly Printed Part
Lever Installed on Board
Repaired Amplitude Control
Working HP 8007B
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