A little candohm assistance

[bigaudioal]

Am going to replace the candohm resistor pictured below in my Admiral Telebar set. Both portions test open. The values are 2725 Ohm @ 2.5 watt and 2650 Ohm @ 10 watt. I just received two ohmite wire wound resistors that should work fine. One 2700 ohm @ 3 watt and one 2500 ohm @ 10 watt. So, well within 10% on the values of both. Now, since I have not replaced a candohm before, take a look at the attached schematic and let me know if I have it correct. R92.

There are only 3 wires attached to the existing candohm. Two of those wires go to the socket plug for the radio/phono set at pins "M" and "N" The other wire goes to a terminal strip in the TV chassis.

I plan on joining the two new resistors together with the wire going to the "M" pin of the plug socket. Then the other end of the new 2700 ohm/3 W resistor to the "N" pin of the plug socket. Finally the other end of the 2500 ohm/10 W resistor to the wire going to the terminal strip in the TV chassis.

Do I have that right?

Thx!

[bigaudioal]

Note: the picture of the resistor is oriented the same as the picture of the schematic. So the yellow wire on the left is going to pin "N," the orange wire to pin "M," and the red wire to a terminal strip in the chassis.

Also, can I use the center terminal of the old candohm as a mounting point? Leave the orange wire there and attach one end of each new resistor there. Then remove the yellow and red wires from the old candohm and connect to the proper new resistors?

[Notimetolooz]

Do the replacement resistors have wire leads? If they do, I wouldn't leave the junction of the yellow or red wire just float in the air. If they are the tubular resistors with solder lugs then soldering one of the lugs each to the center candohm lug should be OK.

[bandersen]

"Should be OK" is the key here. If the open wires inside the candohm resistor were to touch and make contact and you reused those lugs, it could be trouble.

[Kevin Kuehn]

Those values should work. Sometimes (if chassis space permits) you can spread open those candohm mounts and remover the resistance element wire. Then reinstall the terminals and insulation. Mount the replacement resistors to the terminals. Wires stay in their original places.

[bigaudioal]

I think to be safe I would cut off he old unused tabs on the old candohm so there is no chance of them coming into contact with anything. Then the only tab remaining would be the one holding the new resistors.

[earlyfilm]

Originally Posted by bigaudioal

Also, can I use the center terminal of the old candohm as a mounting point? Leave the orange wire there and attach one end of each new resistor there. Then remove the yellow and red wires from the old candohm and connect to the proper new resistors?

Only if you first remove all three wires and check the candohm for center terminal to chassis resistance.

Many candohms carbonize the insulator when they overheat and fail, and that leaves a high resistance path to ground.

Overheating also boils out the wax that was formerly kept the insulator dry and that too can cause them to absorb moisture on a damp day, although this normally is not a problem as they almost never were used in critical circuits.

James

[M3-SRT8]

Originally Posted by bigaudioal

I think to be safe I would cut off he old unused tabs on the old candohm so there is no chance of them coming into contact with anything. Then the only tab remaining would be the one holding the new resistors.

Or, do what I do. Put a length of heat shrink tubing on the now dormant metal tab.

Put the same color heat shrink on the end of the wire going to the new ww resistor nearby. Then you, or anybody in the future, can tell at a glance what you did.

I usually do this when I hang new radial electrolytics underneath canned multi-sections. Red for A, Yellow for B, Blue for C.

Looks pretty.

[bigaudioal]

Thanks for all the replies. Since there is plenty of room around this candohm, I may try and pry it open, gut it and leave the original three tabs and insulation to mount the new resistors to. This way no chance of the original candohm interfering with the new resistors, but will give me great mounting points.

At least I understood the schematic and wiring on this candohm and how to replace it with these two new resistors. Baby steps!!!

Each time I encounter a new part to replace that I have not done before, I learn.

[wa2ise]

I'd remove the candohm resistor completely, and use its mounting holes to hold terminal strips, or if your new power resistors are the kind that are tube shaped with holes, mount them standing up with long screws and flexable washers and nuts, if you have the headroom.

[bigaudioal]

Originally Posted by wa2ise

I'd remove the candohm resistor completely, and use its mounting holes to hold terminal strips, or if your new power resistors are the kind that are tube shaped with holes, mount them standing up with long screws and flexable washers and nuts, if you have the headroom.

DUH! I scored a ton of terminal strips in a free Ham radio equipment grab a few months ago. That will be easiest!! THX!