I picked up a set of NR-5 radios. They appear to be from a storage cener and sat on a shelf for 85 years. Everything looks good. I would like to know.

What approach should I take to supplying power - use large programmable units, build a transformer from 110 AC, what is your recomendation.

What should I use for a speaker/headset?

Thanks,

Troy

Hi Troy

Best to build a power supply. Your radio uses 01A tubes. Each takes 5 volts @ .25 amps on the filament. "B" battery voltage should be 90 with lower voltage for the detector.

Use a high impedance speaker. A modern speaker will work but will require an output transformer.

Schematic for your radio can be found here:

http://www.nostalgiaair.org/PagesByModel/885/M0039885.pdf

Norm

:I picked up a set of NR-5 radios. They appear to be from a storage cener and sat on a shelf for 85 years. Everything looks good. I would like to know.
:
:What approach should I take to supplying power - use large programmable units, build a transformer from 110 AC, what is your recomendation.
:
:What should I use for a speaker/headset?
:
:Thanks,
:
:Troy

www.tubesandmore.com sells power supplies for converting battery radios to AC. The come as a kit for building. You may want to build a separate power supply for the filaments of the tubes of your radio if they draw a lot of current. The tube filaments must receive well filtered DC--use high value electrolytics. If a transformer with say 24 volts is used, a choke (low resistance) can then be used for filtering, with a high value (say 3,000 MFD) electrolytic on each side of the choke. A variable wire wound resistor can be used at the end for bringing down the voltage to the appropriate value. If desired, a more detailed transistor/zener diode system can be used for perfect voltage regulation.

Thomas