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Fuse resistors and 880-100n ohm globar Hallicrafters S 120




 
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September 20, 2018, 01:14:26 PM *
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Author Topic: Fuse resistors and 880-100n ohm globar Hallicrafters S 120  (Read 176 times)
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jimmy
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« on: September 09, 2018, 04:13:55 PM »

Would someone please help me, I am in the middle of trying to repair a S 120. I need help on how to test R20, R21, R22. R20 is 880 to 100 ohms Globar, I think I will need a negitive temperture cofficient thermistor here?  R21 is 33 ohms, 5 watt and R22 is 22 ohms 2 watt and both or fused. Question , how do you check for good or bad? any and all help will be very much appreciated.
Jimmy K5CSU
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w4bfs
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« Reply #1 on: September 09, 2018, 08:28:50 PM »

an All-American 5 minus 1 (the rectifier tube) ... ok get the tube manual and check the filament voltages and currents .... 12 or 50 volts and 150 mA seems about right .... so as you see the filament string is series from the 120 volt line .... will need to know the pilot light ratings for what you have... 47 bulb is 6V 150Ma ... so adding it up is: 6 + 6 + 12 + 12 + 12 + 50 = 98 volts and applying Ohms law
120 - 98 = 22 volts at .15A  gives  about 140 ohm resistor 5W will get the job done to replace a aging globar

there is no power transformer so there is no isolation and a shock hazard .... I would want one added externaly or internally .... the all American 5 would operate from either AC or DC from the old days
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jimmy
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« Reply #2 on: September 10, 2018, 05:20:21 PM »

John just wanted to thank you for your help.
Jimmy K5CSU
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