Posts: 225
Threads: 14
Joined: Oct 2005
City: Grand Blanc, Michigan
You might look as a signal generator and frequency counter if you plan on doing more radios in the future. On the resistors if you still have worries or doubts what is the make up of these? I have seen some that have a cardboard type exterior with metal ends and some that are solid material with metal ends. If it is the cardboard and the size of the cardboard tube is larger than the new style one watt resistors then you could gut the resistor by using a drill and drilling out the core and sliding a 1 watt 5% resistor in and drilling a small hole in each metal end and slide the metal ends back in and solder each lead to the ends and cut off the excess. Typical values for 1 watters is 68K or 75K, either one would work and fall into the 70+/-20% range.
Posts: 111
Threads: 27
Joined: Oct 2007
City: Livonia, MI
I don't know why I didn't just think of this in the first place - the schematic gives the voltages on the plates of the tubes connected to either side of the resistor so it was easy to figure out what wattage it was. I guess the glass encased technology of the 20's component made me forget about Ohm's law and P=VxI
Ended up putting in a 68K at 2 watt that I had.
Also picked up a 38-7 in decent shape that I stumbled on locally through craigslist yesterday. Slowly brought that one up on the variac and works wonderfully although I am still going to recap that one. Also pick up some German and Spanish sounding stations on the shortwave band which was interesting. I like the sound much better on the 38-7, it's nice, rich and warm sounding whereas the 531 seemed a bit flat and more "midrange-y" in comparison. Wonder if the sound on the 531 is due to the Utah speaker and would benefit from a matching transformer and PM replacement, or is this just a characteristic of the 1928 set?
Posts: 225
Threads: 14
Joined: Oct 2005
City: Grand Blanc, Michigan
The 38-7 is a nice radio one of the con-centric tuning units, I have the 38-4 (8 tube version) and yes they are nice radios, not that hard to work on since they don't have the subchassis of the magnetic tuning models. They were only made one year (1938) with this style dial.
