I received the new electrolytic capacitors from Hayseed Hamfest and replaced them successfully. The main power supply cap(s) were easy, but one was on a small PC board and since all interconnects are wired with no connectors, it can be a challenge.
It might be a little low in the output power. In those days it was spec’ed by input power, and 90 watts was full power. Output power looks reasonable, between 50-60 watts. The final tube plate voltage is high, I might need to look at that some more.
Overall, seems to work OK. My main issue is with the plate current meter. It swings wildly when sending CW. I can dip set the plate current fine, and adjust the power out. But if I set the plate current at about 150mA (about 1/2 scale), the meter will overshoot on each key press to about full scale (300mA), and just fly back and forth between 0 and 300mA.
The meter is right in the cathode circuit, so shunt, just inline between cathode, a 15 ohm 2 watt resistor and ground.
My homebrew xmtr has a similar plate meter circuit design, and works normally (current goes right to set value when keying).
My rig is serial #0125, quite early. They redesigned the meter circuit (sometime before #0620). It uses a shunt resistor, a pot, and a capacitor, and needs calibration. I’ve seen videos of this configuration and it works more like one would expect.
Apparently, Drake attempted a fix by adding a capacitor across the meter, some time before the complete redesign. I have seen a couple mentions of this, but no schematic, service bulletin, or anything can be found about it. I did try it though, without results.
I have also read Drake was known for using cheap meters, in most or all of their radios. I don’t know if mine was always this bad, or if age has made it worse.
Since I can still set the plate current and power level, I can live with it, but it is a bit distracting when sending.
In the slim chance someone has parted out a 2-NT or had a spare meter, I have put out a query on the Drake mailing list, but I don’t expect any hits.
I found another 2-NT for sale in Minneapolis on Craigslist. It looked OK and was a good price. Then they dropped it by $50. So I contacted them. Since I am leery of online scams where people re-use photos, I asked him to send me another photo with a piece of paper with the date handwritten on it. I never heard back.
But, I have been making contacts with it. I also made a cable to interface my Eico 722 VFO. I took and old crystal in a FT-243 holder and removed the crystal, drilled a hole in the back and connected a piece of RG-174 to the pins. Connected it up to the 2-NT and seems to work fine. I did have an issue with the 722 however. Every once-and-a-while, it would jump about 8 kHz, or start drifting (usually while in a QSO), then jump to another frequency. This also was happening when using it with my homebrew rig.
The 722 was known as a pretty good and stable VFO. So I dug into it yesterday. I replaced a couple of resistors that were out of spec or didn’t look great. I also re-soldered some connections and redressed some wiring. So far, so good, but we’ll see.