![\"Old](\"https:\/\/www.n4rfc.com\/wp-content\/uploads\/2014\/10\/HP-24-OldNew.jpg\")
<\/a>Old and New Electrolytic Caps<\/p><\/div>\n
Of course, to start with you need to get the old caps out. \u00a0Just in case you have an open bleeder resistor, carefully short the HV output terminal to ground to discharge any caps that may still have a charge. \u00a0As old and leaky as these caps are by now, this is probably not necessary, but I just hate nasty surprises with high voltages! \u00a0Start by removing the top cover, bottom cover, then remove the two screws that hold the diode board under the chassis. \u00a0The diode board is mounted on two phenolic stand offs below the caps. \u00a0 You will have to unsolder the green wire from the top of the diode string that goes to the HV terminal to fold the diode board back out of the way.<\/p>\n
<\/a>The original 50 year old wiring<\/p><\/div>\n
With the diode board moved, you can see the original capacitor wiring. \u00a0That wire coming from the transformer with the extra tubing on it goes to the center point of the six caps that are in series. \u00a0Unsolder that lead and pull it back out of the way too.<\/p>\n
Remove the 100K ohm resistors, wiring, and finally the caps. \u00a0Un-solder any of the wires that are attached to the caps. \u00a0Unscrew the phenolic mounting tabs with the cans attached. \u00a0Once the caps are out you will see there are nylon inserts that the phenolic mounts were screwed into. \u00a0I suspect these were used to increase the insulation and spacing on the higher voltage end of the capacitor string.<\/p>\n
<\/a>Chassis with caps and wiring removed<\/p><\/div>\n
Pry the nylon screw mounts out of the chassis with a flat blade screwdriver.<\/p>\n
I used a 4.5\u00a0X 6.5 piece of FR-4 perf board with a .1″ pattern of .062 holes to mount the caps. \u00a0I trimmed the perf board down to just cover the can cap mounting holes up to about 1\/8 from the edge of the chassis. \u00a0As mentioned above, I selected a Snap In type electrolytic that had .062 wire leads which allows the caps to snap tightly into the perf board. \u00a0Trim the board to fit over the original capacitor mounting holes without over hanging the chassis top. \u00a0Mark and drill the perf board where the two screws for the diode board standoffs, and use those screws to mount the perf board to the metal chassis. \u00a0 \u00a0The chassis should look like this when you are finished:<\/p>\n
<\/a>Prepped Chassis<\/p><\/div>\n
Snap the caps into the perf board centering them in the original capacitor holes in the metal chassis and orient the leads so that you wire the caps in series starting at the ground near the corner of the transformer and positive leads so that the caps can be wired in series from the ground at the corner of the power transformer, to the last positive terminal near the HV connector.<\/p>\n
<\/a>Note the orientation of the negative sides of the caps<\/p><\/div>\n
Start with the 100K \u00a02 W resistors. \u00a0I replaced the originals with some new metal film 2 W units from Mouser.com. \u00a0Form the leads and J-hook them on to the caps leads. \u00a0A small solder join will help old them in place while you complete the wiring. \u00a0Small solder joints! \u00a0Don’t over do it or it will be hard to J-hook the wires on to the small leads on the caps.<\/p>\n
Then wire the caps together. \u00a0I used solid wire so that I could dress the wiring away from the metal (grounded) chassis. \u00a0Daisy chain from the positive of one cap to the negative of the next.<\/p>\n
<\/a>Lift the reistors up away from the Perf Board<\/p><\/div>\n
Pay attention to the routing of the wires, keep them away from the grounded chassis.<\/p>\n
<\/a>This is what it should look like when you are done wiring<\/p><\/div>\n
Replace the 40 uF bias supply cap on the diode board before you screw it back down to the standoffs. \u00a0Connect the red-yellow \u00a0wire from the transformer (with heavy tubing insulation) to the positive side of the third capacitor. \u00a0Then put the diode board back into place and make the final connection from the diode board to the HV connector.<\/p>\n