[Hallicrafters] R-274 Band VI Update

[Thomas Hoyer]

Band VI update:


Issues with band 6 not functioning - swapped the OSC turret section with the one from band 5 and I now had VFO operation in band 6 - not correct freq, but operation. This narrowed my issue specifically to the band 6 OSC module.


I carefully removed and measured all of the caps and each was well within the tolerance for the value. Reassembled the module and retested, same issue. Tried to think of a good way to test the module out of the radio - pulled out the trusty old B&W dip meter. Tacked a cap across the terminals where the VFO cap would connect that would represent the approx mid point of VFO travel. Tested with the dip meter and it seemed to resonate around 36mhz - about 10mhz too low. For a sanity check I removed the band 5 module and ran the same test, results were good, dip freq was approx mid band plus 6mhz for band 5.


I started changing the cap values in the band 6 module and ended up substituting in a 20pf cap in place of the combined 55pf cap to get a resonance around 45mhz which is where I wanted it. Got a little too late to try it in the radio so tonight I'll run a couple tests. I'm a bit surprised at the drastic value change to get the module to resonate. Leads me to think something else is amiss...


Tom
W3TA