[MrFixr55]

Hi Prof T Russell,
+1 on Morzh's comments.

Yes, for testing purposes, you could hook the remnants of the OEM speaker to the radio and hook a PM speaker to the secondary of the output transformer. For testing purposes, a mismatch between transformer impedance and speaker voice coil impedance is not horribly important. For the permanent repair, however, if replacing the OEM speaker with a PM speaker, the impedances should match. The 7B5, 6K6 and 41 are essentially the same tube. B+ for the output stage on this set is 180V. The 1940 RCA Receiving Tube Manual states to use the 6K6 specs for the 7B5. However, the specs for the 6K6 in this manual does not list Plate Load Resistance at 180V. for 250V, the Load Resistance is 7600 Ohm. However, the 1937 RCA Receiving Tube Manual lists a Plate Load Resistance of 9000 Ohms for the 41 at 180V.

The field coil can be substituted with a 1700 Ohm resistor with a minimum of 10 Watt capacity. It is recommended to increase the capacity of the filter caps to maybe 20 uF for the first cap and 3o - 47 uF for the second cap. Monitor the B+ to ensure that it does not increase too greatly. A choke with a resistance of 1700 Ohm can be used but I don't know what the inductance would be.

Funny comment about the radioactive dust and hantavirus, but do be careful. At the least, sensitization to hantavirus can cause erroneous test results on a lot of tests for therapeutic drugs like digoxin, some antibiotics, etc., which use immunochemical techniques involving mouse derived antibodies. At worst, hantavirus respiratory syndrome can kill you. Definitely wipe the cabinet and chassis down. Keeping things wet with 70% isopropyl alcohol is effective. So is 10% dilution of fresh household bleach, but hey, you do want this thing to work.

We all make mistakes, some little, some spectacular. You did learn an important lesson. Electronic, electrical and mechanical systems work on smoke. How do I know this? Because when you let the smoke out, the device stops working. I was once working on an old HP computer terminal (from the days of mainframe computers) with an analog voltage regulator for the 5V supply. There was no output. I found a Zener diode that was across the output to be shorted so I cut it out of the circuit. I then powered it up, after a few seconds, I heard some funny ticking noises. I noticed the smoke just before the filter caps blew off the PC Board leaving a stream of paper, aluminum and electrolyte. The can hit the wall 12 feet away. Every chip cracked open like your resistors. It didn't dawn on me that the Zener shorted because the pass element shorted and put about 35V across the caps and chips after i cut out the Zener. With both parts shorted, the transformer and a dropping resistor of high wattage were handling the voltage drop.