Resistors,rheostats,potentiometers

Sadly I have not found a replacement for the globar or a suitable workaround, so I too am using a variac to bring it up slowly. The BFO works as it should, but I did clean the switch thoroughly. Still hoping to find the holy grail globar, but in the meantime the variac works fine!

Good repair!

How did your radio project turn out? Did you find a replacement for R20 (Globar) in your Hallicrafters S-120 receiver? 

When I fire up my S-120, I continue to do so with a Philmore Variac. It might have had a weak [You must be registered and logged in to see this link.] bulb in there that time I turned it on after the repairs were made and one of the bulbs burned out. Just the same, I have felt safer using the Variac with it.

One other mention on the S-120: I had trouble with the BFO control ever since I got it. The radio became unstable and tended to motorboat when the BFO control was turned up. I have read that others back in the 1960s managed to copy CW and SSB with their sets. Well, I kept trying to use it and recently I noticed that sometimes the BFO would perform wonderfully well when turned on. I finally found the trouble with it. The switch on the control was not working right. It was supposed to ground the AVC line when the BFO was turned on. It was not doing that-not consistently anyway. A shot of control cleaner into the switch of BFO control took care of it. Problem solved!

I have found a .25 amp 120v 30 ohm thermistor made by Ametherm. Would this do what I need?

I have looked around previously for a suitable replacement globar type (now an obsolete term?) but found they were either the wrong resistance range (low Ohms) or made for use at high currents. These units were generally made for use in tv sets not radios.

Keep in mind that the filament current in the S-120 is 0.15 Amperes. A Globar/Thermistor rated for 1.5 Amps is not going to help here.

Keep looking around for a replacement. You may find something suitable. Just remember that there is not much room under the chassis for a bulky device. In my S-120 it took about a full minute for the set to finally come on with the original glowbar in place. Current warmup is about 10-12 seconds. 

I might add that the original glowbar unit in my S-120 did not go bad on its own but from my bending it a bit to one side to make room for a new electrolytic and that was enough to damage it. Apparently, they are rather fragile.

I have considered the NTC thermistor, but I'm unsure of the rating. The lowest I've seen is 1.5 amps. Is this low enough?

HMMM, Just a thought depending on the wattage, could a NTC thermistors for
inrush current limiting work?

Theoretically a 100 Ohm 5 watt resistor (same as the globar's hot resistance) should work but the series string turn on current will be high and might blow out the dial lights. I ran into this problem with my Hallicrafters S-120. I used a 130 Ohm 5W resistor replacement in mine. This brought the total voltage drop for the filaments to 120V (at 0.15 Amps). But a 150 Ohm 5W resistor might be a better choice especially if your line voltage is higher. I am now using a Variac to bring up the line voltage to 120V and this is preventing anymore dial lamp blowouts. Good luck with yours.

Rod Clay  WB6FBF

I need a replacement or workaround for a globar resistor 880/100 ohms for a Hallicrafter S-120. Can anyone help?

Define issues and ask questions of what, why, where about resistance.