As noted elsewhere, I identify the radios I have by the order in which I acquired them.
This page is about trying to make the 7th one actually run again. This is the
last acquired of all the radios.
I say 'blog' because it turned out to be a list of what I did, not what you're supposed
to do. If you're bored, you might find it interesting.
See here for info on the original radios.
The 7th radio was sold as restored and fully functional. It included an originial speaker cabinet. It
had been recapped. It worked sort of. It even came with an embroidered cover for it.
The following pages address the things I discovered in more or less the order I took.
While comparing circuitry to the 5th radio, I discovered that SW8-14 was wired completely wrong and that the wafer had been installed backwards.
While playing with oscilloscopes and signal generators, I discovered that it may have been recapped but it certainly wasn't aligned. This is actually a good thing because now I have two radios to use for the development of the align procedure.
I did a local oscillator alignment and an IF alignment. The crystal is prett bad in this radio so things were right on the edge. I did get it
to detect a 1.4 MHz signal with the dial set to 1.4 MHz. It was way off before I started.
I also got the various Selectivity Switch crystal settings to work as expected.
I did all the work for the Antenna Matching page and built the 1st circuit.
Hooking up the signal generator, I was able to hear a 1.4 MHz modulated signal with the generator output set to around 40 mV p-p. That's fourty times 'best case' of 1 mV.
Having done no work at all on the RF stages, I tried swapping out V2 (6SK7) and V3 (6SA7) to see if better results could be achieved.
The procedure was reduce the signal generator level until I could no longer hear the signal and write down signal gen levels. For a half dozen tubes of unknown value for V3, the best case was about 30 mV and the worst about 50.
I put the best tube in the V3 socket (which was the original) and repeated the process with V2. I got approximatly the same results: different tubes yielded slightly poorer results. Makes me wonder if the RF stage alignment is particularly tied to the tube. It would be surprizing as the other parts of this radio were so far off.
Page: /7th_radio_resurrection/Resurrect_7.shtml
Last modified: Thursday, 2 Jul 2026