Early Freshman Masterpiece

[fsjonsey]

Hello everyone,
Last week, I picked up a 1924 Freshman Masterpiece For $15 at an a antique mall. The other day, I popped in a set of 01A's, connected a 6V 5AH SLA battery from an exit sign as an A battery, and used 10 9 volt batteries in series, tapped at 45V for the Amplifier and Detector B+. Plugged in my RCA 100a Speaker, connected a 100ft long wire antenna, and fired it up. No dice.

I finally had a chance to open it up tonight, only to discover that both of the audio interstage transformers were missing. I replaced them both using this cap/resistor mod:

Finally, I have audio, but it's extremely faint. Also, the only range on any of the three dials that will barely pick up a station is about 92-100 on the 0-100 scale tuning dials (all dials are set to the same position). Below 90 or over 100 and the set goes completely silent. Any tips on working with this dinosaur would be greatly appreciated. This is the first three-dial TRF set I've ever owned. The oldest set I've had any experience with prior to this is a Radiola 18.

[Kevin Kuehn]

If I'm not mistake the 100A was intended to be driven by a 71A. So you're not exactly going to have room filling volume driving it with a 01A. Have you tried listening with a high impedance headset? What model Freshman is this, got a schematic link?

[old_coot88]

I would try some progressively lower values for the plate load resistor, to see if volume improves any.
If no improvement, try going up in value, say maybe 220K, 330K etc.

[bob91343]

A signal generator would be helpful. Perhaps the tuning capacitor shorts when you turn it past some point. You could measure the sensitivity and know exactly the effect of each change.

[Reece]

Ditto re: the plate resistors. Check the plate voltage on those tubes and compare to what the tube manuals say. The last stage may require more than 90 volts, some of the three-dialers do, but it would be obvious from the radio's power terminals.

[fsjonsey]

Thanks for the replies everyone! I lowered the plate resistor value to 50K and volume has improved dramatically. I also figured out the lack of sensitivity. I had the set connected to a wire antenna that was way too short. As a result, I was only able to pick up the 500 watt AM Daytimer that broadcasts from 10 miles away.

[old_coot88]

Dang, I was gonna suggest 47K as a starter, but thought the better of it as that sounded too specific.
Glad you got her singing good.

[wa2ise]

I've heard it said that an old Ma Bell telephone ringer with a two winding inductor would work as a replacement transformer here. I've never tried it, though...