![\"Drake](\"https:\/\/www.n4rfc.com\/wp-content\/uploads\/2016\/03\/2ntlrg.jpg\")
<\/a>Drake 2-NT CW Transmitter<\/p><\/div>\n
I wanted to put together a vintage CW station, something that would be what a Novice station of years ago might be and it seemed that the Drake 2-B receiver and the 2-NT transmitter would be a great pair. I was using a Johnson Ranger with the 2-B for CW, but the Ranger is a very big and heavy transmitter for a 75 Watt (power input to the final amplifier stage) novice transmitter.\u00a0 Plus, it was clunky to operate, it was not setup for semi break in keying.\u00a0 Now, I like vintage, but let’s get real, I want to be able to actually use the rig the way I am used to working CW.<\/p>\n
After checking out the 2-NT I found that there was a little hum on the transmitted signal.\u00a0 This transmitter is close to 40 years old, and in these older radios one of the things that needs attention, besides the tubes, is the Electrolytic Capacitors.\u00a0 The electrolytic capacitors are used as power supply filter caps, so when you see hum on the signal you can bet that the caps are going bad.\u00a0 The electrolyte in the capacitors drys out over the years and the filter caps don’t do a good job of filtering the rectified AC power into pure DC voltage.\u00a0 So I decided to “recap” the 2-NT with new, fresh, electrolytic capacitors.<\/p>\n
Most of these older rigs used what were called “Can” capacitors.\u00a0 The can contained several large value capacitors in a single chassis mounted aluminum can.\u00a0 (I.E. the name Can Capacitors)\u00a0 With the advent of solid state electronics these high voltage can capacitors have gone away.\u00a0 They can be had from specialty suppliers like Hayseedhamfest.com, but they can be pricey.\u00a0 Since there was plenty room under the chassis for axial leaded capacitors,\u00a0 I elected to go with them for this re-cap.\u00a0 They work just as good and without pulling the bottom cover off the radio you would never know the difference.<\/p>\n
Here is what we started with:<\/p>\n
<\/a>Before – Click on image to see a larger version<\/p><\/div>\n
There are three capacitors in the can, a 60 uF for the “bottom” half of the voltage doubler for the High Voltage supply to the final, an additional 40 uF for the low voltage filter, a 20 uF for the screen voltage supply for the final.\u00a0 There are a couple of axial leaded caps, one 60 uF 450V for the “top” half of the voltage doubler and a smaller 20 uF cap for the negative bias supply.\u00a0\u00a0 In shopping for caps, I found that you can’t always get the exact replacement.\u00a0 I had availability of 80 uF for the HV and LV supply, (originally 60 uF) and 22 uF to replace the original 20 uF caps.\u00a0 I ordered the caps from Mouser.com and had them in two days.<\/p>\n
The can capacitor has lugs on the bottom that are very convenient for wiring, the leaded caps needed something to be wired too.\u00a0 So, I added two terminal strips.\u00a0 The first one I soldered to the chassis where the cap ground leg was soldered.\u00a0 That strip had one ground, and three open terminals.\u00a0 I moved the original wires from the can to the open terminals then wired the axial caps to them.\u00a0\u00a0 I added one more ground terminal under one of the screws for the power transformed and wired the ground end of the 40 uF and 80 uF caps to it.\u00a0 The the final cap was the 22uF for the bias supply, the positive side goes to the ground on the 4 terminal strip and the negative lead to the circuit board where the original cap was wired.<\/p>\n
So, after it is wired up this is what we have:<\/p>\n