Cost To Date

Tubes, TubeDepot, $23.75
Tube, VacuumTubes, $10.00
Filter Caps, Digikey, $2.05
Filter Caps, Digikey, $3.15
Paper Caps, Digikey, $24.28
Knobs, Bias Pot, IF Xformer Play Things of the Past, $31.35
Speaker Connector, NAPA, $2.96
Transistor, Quest Components, $32.50
Weld Nuts, McMaster-Carr, $2.00
TOTAL $132.04

Saturday, November 30, 2013

The Tubes

Awesome tube reference:


I removed the echelon glass, cleaned it and put it together temporarily to see how well it will look. The good news is that the silk screen on the glass is in perfect condition.

Here are a couple of videos:

Radio Delivered

While starting the restore of Studebaker AC-2905 radio (AC-2905 Restore), Brian found a more desirable radio for his Transtar truck. In anticipation of starting the restore Brian sent me a couple of pictures. The first thing I noticed was a big power transistor on the side of the radio and thought that this will be a more modern transistor radio. But this is not to be. Interestingly, looking inside the radio we find several tubes. So this radio is an odd hybrid. After checking it out some more I then find that the lone power transistor is the audio output transistor not the vibrator replacement. On further analysis I find that the tubes are the very odd 12 volt type!! Normally vacuum tubes require a high voltage to operate, in the order of 100 to 200 volts. These tubes that were developed on the verge of the development of the transistor could operate on 12 volts!!

 Top of radio and spare fuse holder that Brian provided

 Front with one of it's teeth pushed in

Brian did some cleaning
Volume/tone control shafts
 Motorola Model number SM9T

Front cover removed
 See that big power transistor on the side?

Back side

Closeup of the power transistor

 Comparing the two bezels. Note that the dial is backwards on the Transtar radio. On normal radios the dial goes from left to right, 550 KHz to 1600 KHz.

Lots of dirt in the top
Bottom fairly dirty also. The tube on the bench to the left was just sitting in the radio. The sockets do seem very loose and for some reason they mount the tubes upside down in the chassis. Maybe they wanted the tubes to fall out?

Update: I did some more testing and was able to get some noise out of the speaker so it looks like the power transistor output stage is working. Can't say much for the rest of the radio. In several days when Brian gets the schematic to me I'll be able to do some more in depth testing and maybe get this puppy to put out some tunes!!!