I have a couple of Zenith radios one Model 5S127 and one Model 4B131. The 5S127 is an AC model and uses a type 44 (.025A) bulb for the dial lamps. The 4B131 came to me without a pilot lamp and is a 6 volt battery set. Question, can anyone tell me what lamp the 4B131 used? Was it the same as the 5S127 electric set? I need to know exactly what bulb was used because it is in series with two of the tube filaments and in parallel with a small resistor. I don't want to risk damaging the tubes with an incorrect pilot bulb. Dave

:I have a couple of Zenith radios one Model 5S127 and one Model 4B131. The 5S127 is an AC model and uses a type 44 (.025A) bulb for the dial lamps. The 4B131 came to me without a pilot lamp and is a 6 volt battery set. Question, can anyone tell me what lamp the 4B131 used? Was it the same as the 5S127 electric set? I need to know exactly what bulb was used because it is in series with two of the tube filaments and in parallel with a small resistor. I don't want to risk damaging the tubes with an incorrect pilot bulb. Dave

Hello Dave,

The service data for the 4B131 is in Riders volume 7, pages 1 and 2. On page 2 I believe it shows the lamp to be a 6 to 8 volt lamp. I am not sure of the lamps current. I would think probably 6 volts at .150 amp. Perhaps someone else on this site may have a better idea.

Radiodoc

6 to 8 volt lamps were commonly used in automobiles due to the electrical system used within autos of the day (working from 6 to 8 volts just as our new cars work from 12 to 14 volts, depending on what speed the engine is running at and what kind of load is imposed upon the generator/alternator, as well as what the top voltage is set for at the regulator--usually 7.4 volts with 6 volt cars and 13.5 volts with 12 volt cars).

Still, that doesn't say much about the amperage of the bulb required for your radio. With a 6 to 6.5 volt supply wired to the radio, insert a #47 bulb and work up from there until each #15 tube has the appropriate voltage across the filament +/- 5%. The current draw of the #15 tubes will likely require a higher amperage bulb, but it is good to start with a #47 bulb. You may use a 7.0 volt supply with this radio, but the voltage across the 6.3 volt tubes should not exceed 6.5 volts.

Thomas

:I have a couple of Zenith radios one Model 5S127 and one Model 4B131. The 5S127 is an AC model and uses a type 44 (.025A) bulb for the dial lamps. The 4B131 came to me without a pilot lamp and is a 6 volt battery set. Question, can anyone tell me what lamp the 4B131 used? Was it the same as the 5S127 electric set? I need to know exactly what bulb was used because it is in series with two of the tube filaments and in parallel with a small resistor. I don't want to risk damaging the tubes with an incorrect pilot bulb. Dave

hi the radio diagram book says it uses a #40 bulb also looks to be the same chassis as a 4b106 and a 4b132. butch