10-07-2014, 10:53 PM
Tonight I decided to tackle the 2 candhoms. So I desoldered the wires, labeling them as I did so, and drilled out the rivets.
One was a 2 section candohm (part 124 - 1k and 4k sections) where the 4k section opened up, and someone subbed in a 4k tubular ceramic. Surprisingly, they even did it the proper way with a new terminal strip, and didn't reuse the open terminal like many of the candohm repairs I have seen. The other one was behind it, and not easy to see until I got them out. It's a single section (part 118 - 14k) that still reads good.
However, I have never quite seen a casing like this on a candohm. Instead of the usual metal shell with fish paper around the resistor, its encased completely in black plastic, and has a metal strip around it to hold it in place. According to the part list, it's just labeled "Resistor (14,000 ohms, 1/2 watt)". This seems like a rather large package for just a 1/2 watt resistor. Given that it was a candohm, i just assumed I should go for a 10w replacement, despite the part list calling it 1/2w.
Not trusting the part lising of 1/2 watt for a candohm, I decided to replace it with 10w. 10w is usually my go to for candohms, as I don't want to power the radio on to find the voltage drop to calculate the actual power. So I go with 10w. It usually gives me enough of a safety/cooling factor as well.
For the 14k resistor, I made up a replacement of two 7k 5w resistors in series to give me 10 watts of power handling (I figured 2 7k's in parallel would be just the right length, and a smaller diameter than a 10w 14k). You can obviously see how I made up the replacement, as I had temporarily screwed the terminal strips to it so I could get the spacing correct. I had angled the terminal strips to get me the proper horizontal spacing and height. And it's a good thing I did. one of the straps was behind the power transformer, so there wasn't much clearance. Luckily I was able to get a good enough angle, it cleared the transformer. Attached it to the chassis in the existing holes, and wired it back up.
For the multisection candohm, I took the same approach - 5w resistors in series for a combined 10w. I couldn't get the horizontal spacing exact for the terminals. But there was enough slack in the wires, and i hit the existing holes perfectly. So it worked out pretty well. Here is how I built it using the outside of the chassis. Since it's a downward shot, you can't see that I had screws in the chassis in the existing holes. That gave me a perfect way to align and solder everything. The terminal strip between the sections is currently floating however, as there is no hole there. I debated drilling one, but it really doesn't move much. The resistors and wires keep it steady. And it does it's job of preventing it from shorting against the chassis. There isn't anything near by that it could short on anyway. And it's not like monkeys are going to be banging on it and trowing it around. I could also get out my big Weller gun and solder it to the chassis wall too. Maybe I'll do that, just in case.
One was a 2 section candohm (part 124 - 1k and 4k sections) where the 4k section opened up, and someone subbed in a 4k tubular ceramic. Surprisingly, they even did it the proper way with a new terminal strip, and didn't reuse the open terminal like many of the candohm repairs I have seen. The other one was behind it, and not easy to see until I got them out. It's a single section (part 118 - 14k) that still reads good.
However, I have never quite seen a casing like this on a candohm. Instead of the usual metal shell with fish paper around the resistor, its encased completely in black plastic, and has a metal strip around it to hold it in place. According to the part list, it's just labeled "Resistor (14,000 ohms, 1/2 watt)". This seems like a rather large package for just a 1/2 watt resistor. Given that it was a candohm, i just assumed I should go for a 10w replacement, despite the part list calling it 1/2w.
Not trusting the part lising of 1/2 watt for a candohm, I decided to replace it with 10w. 10w is usually my go to for candohms, as I don't want to power the radio on to find the voltage drop to calculate the actual power. So I go with 10w. It usually gives me enough of a safety/cooling factor as well.
For the 14k resistor, I made up a replacement of two 7k 5w resistors in series to give me 10 watts of power handling (I figured 2 7k's in parallel would be just the right length, and a smaller diameter than a 10w 14k). You can obviously see how I made up the replacement, as I had temporarily screwed the terminal strips to it so I could get the spacing correct. I had angled the terminal strips to get me the proper horizontal spacing and height. And it's a good thing I did. one of the straps was behind the power transformer, so there wasn't much clearance. Luckily I was able to get a good enough angle, it cleared the transformer. Attached it to the chassis in the existing holes, and wired it back up.
For the multisection candohm, I took the same approach - 5w resistors in series for a combined 10w. I couldn't get the horizontal spacing exact for the terminals. But there was enough slack in the wires, and i hit the existing holes perfectly. So it worked out pretty well. Here is how I built it using the outside of the chassis. Since it's a downward shot, you can't see that I had screws in the chassis in the existing holes. That gave me a perfect way to align and solder everything. The terminal strip between the sections is currently floating however, as there is no hole there. I debated drilling one, but it really doesn't move much. The resistors and wires keep it steady. And it does it's job of preventing it from shorting against the chassis. There isn't anything near by that it could short on anyway. And it's not like monkeys are going to be banging on it and trowing it around. I could also get out my big Weller gun and solder it to the chassis wall too. Maybe I'll do that, just in case.
