Some progress made on the 2-C. Got it pretty well cleaned up. The front panel is important to me, and it is probably an 8.5 out of 10. Not perfect, but pretty good. I didn’t use anything harsh on it. Knobs are good. The top of the chassis has pitting that is due to the copper plated steel material (at least the corrosion looks like rust). Everything I read or watched online said you can’t fix it without removing the copper plating. Best you can do is clean it, and if you want, put a clear coating of some type over it to help stop further degradation. I’m undecided about that at the moment. It is fine on the underneath side. Interesting that some metal connectors and hardware, have a thin yellowish layer of corrosion, or some buildup. It cleans off fairly easily. I wonder if it is related to the copper plating somehow.
I have powered it on carefully, and no critical issues seen. The biggest problem I found was that the AF gain pot did nothing until it was about 2/3 fully clockwise, and then it was much too loud. I had to use the RF Gain to control the volume. But I was hearing signals, and it seemed everything else was working OK.
Looking at the schematic, the AF gain was a 3K ohm pot. The shaft is about 1.5 inches long, because the chassis is setback from the front panel by maybe 3/4 inch. I started searching online, and 3K pots are hard to find. Especially these older style pots. One with a 1.5 inch shaft, even harder.
With no luck finding one, I reached out on a RL Drake Facebook group, and had some usual suggestions and tips. People said these pots can be found, but the couple that sent links, did not have that pot, or anything even close.
I found out that the bad pot was made by CTS, so I searched to see if I could find a 3K pot (or close) made by CTS. I did, at Surplus Sales of Nebraska. So I ordered a couple, plus a couple more 3.5K pots with longer shafts, just in case.
I had taken the old part apart, so it seemed like I could swap out the longer shaft and wiper to the new 3K pot. Here is a pic of the old pot internals, with 2/3 of the carbon trace gone.
The pots come apart easily, just 4 metal tabs to fold back and disassemble the pot. I put the old shaft in the new pot, unsoldered the old pot and soldered in the new pot.
Fired up the receiver, and AF Gain now works as it should. Tomorrow the new electrolytic caps arrive from Hayseed Hamfest. The main filter cap should be fairly easy, but the others are on various small circuit boards. The interconnects seem to be soldered instead of using connectors, so some unsoldering will need to be done before I can pull the boards and replace the caps. Stay tuned.
The 2-C re-cap kit came the other day from Hayseed Hamfest, and I found time to install them. The kit included the main filter cap (3 part), and 6 other electrolytic capacitors. First I tackled the main filter cap, as it looked the easiest. The 2-C has a small chassis for 60s era receiver, but there was room to work. Fairly easy to unsolder the three main terminals, but the ground took a lot of heat, and even so I had to cut off the bent over terminal and leave it soldered to the chassis. The new one fit right in, and I bent over the tabs to hold it in place, and soldered the one for the ground to the pile of solder from the old one. Everything looked good so I fired it up and everything seemed fine.
The other capacitors looked like a challenge, so I waited a day before I attempted it. First I identified on the schematic what capacitors were to be replaced. Hayseed just provided the values, so I had to look it over. Some of the new ones were slightly different values, as indicated on the Hayseed Hamfest website. But I found them all, now I needed to physically locate them in the radio. The 2-C has a few small circuit boards, mounted vertically under the chassis. Sadly, there are no connectors, and all inter-connections are hard wired, with little to no slack in the wiring. Most boards have several bare solid wires soldered to the boards, in addition to stranded insulated wires and coax.
Un fortunately, all six of the other electrolytics are on one of three PCBs. Most of the caps were vertical, with top side not too hard to get at, but the bottom lead was near impossible. It looked like one of the boards, part of power supply, had 3 of the caps. It also had no bare wires hard wired, just some harnesses and single wires. Two screws held the board on the chassis. It looked like if I removed the two screws, I could rotate the board enough to solder/unsolder on the back. It worked, now on to the 3 hardest ones.
I don’t know if they make any long narrow tips for my Hakko soldering iron, but I could have used one. The first board had two caps also mounted vertically, with the bottom side very hard to get to. I was able to remove the two screws holding the board down, but really no movement. So I started unsoldering wires from the board. I got all the bare wires first, they were going to the band switch, and had no play. I ended up removing 5 or 6 connections, and I could kind of get to the bottom side where the caps were soldered. Some insulation was harmed in the making of this modification, but I got them in. These particular two capacitors probably took me over two hours.
The last one was also a difficult one, but I used similar techniques, and got it swapped out. I don’t feel bad about replacing 52 year old electrolytic capacitors, but the were still working, and though I didn’t check them all, ESR looked good and values were not too bad. But it is all to make the radio perform at it’s best,
So I checked everything over, did some continuity checks, etc, and powered it up. I hear static but, so signals. Checked all the usual stuff, I didn’t see anything wrong. 40 – 10 seemed dead, the Preselector was not peaking up the noise, which it was the other day.
But I was hearing signals on 75 meters. It is a bit confusing on a 2-C, as for 80/75 meters, the frequency dial flips, with higher frequencies counterclockwise, and lower frequencies clockwise. It is the opposite on 40-20-15. Also, the USB/LSB switch is reversed. It is all color coded, but I wasn’t used to it. Anyway, it seemed to me a problem with oscillator or mixer. One of the boards could have been involved where I made changes, so I went over everything again. I found nothing wrong with the work I did. So I kept looking. I found one resistor not soldered properly to one of the mixer tubes. Ah, that must be it. Soldered it back to where it belonged, no help.
I recalled one time when I first powered up the radio when I got it, where there were no signals, and doing some inspecting, and next time it worked, and subsequently it worked several times when testing it. So I thought maybe there is an intermittent somewhere. So I flipped over the radio, and probed the chassis with a small wooden dowel, looking for anything intermittent, concentrating on the oscillator, mixers, etc. The radio has three crystals setting various IF frequencies, and also has another socket and switch for changing crystals to alter band segments (like 10 meters). I had looked very closely in this area, and resoldered a couple of connections. This time, I put some extra pressure on the slide switch that switches between the standard crystals and an accessory crystal. The radio sprung back to life. That was it, a bad switch. I thought for sure I had one around but could not find. I guess I will have to find some other parts to buy to meet the minimum order requirement at Jameco. For stuff like this, I miss Radio Shack.
I can usually get the radio to work by biasing the switch. I like the radio so far. The bandspread is not as good as my HQ-110, but the .4 kHz filter is nice for CW. The HQ-110 has the Q-Multiplier, but I think the 2-C wins there. But hard for me to compare side-by-side. Maybe one day I can try to set that up.
The Drake is maybe 10 years newer design. It’s smaller, more modern than the Hammarlunds. A bit lighter too, with some solid state devices. Now off to look for a 2-NT. The pair were designed to work together, and I hope I can find one, but it may take a while.