08-25-2011, 09:28 AM
An internet search turned up this website:
http://www.vcomp.co.uk/tech_tips/transfo...ormers.htm
Notice they suggest 22K to replace a primary winding of an audio interstage or IF primary, and 200 pF as a coupling cap in an IF transformer.
I felt this information could apply to my bad RF coil.
I used 15K instead of 22K to keep from significantly reducing the plate voltage of the 7C7 since the 40-125 is an AC/DC set and the B+ isn't very high. As it turned out, the repair worked so well that I didn't bother to measure the plate voltage of the 7C7 post-repair. I probably could have used 10K or even 5K. Maybe I'll pull it back out of the cabinet and measure the 7C7 plate voltage later on.
And since I had some 250 pF caps on hand but no 200 pF caps, 250 pF is what I used.
http://www.vcomp.co.uk/tech_tips/transfo...ormers.htm
Notice they suggest 22K to replace a primary winding of an audio interstage or IF primary, and 200 pF as a coupling cap in an IF transformer.
I felt this information could apply to my bad RF coil.
I used 15K instead of 22K to keep from significantly reducing the plate voltage of the 7C7 since the 40-125 is an AC/DC set and the B+ isn't very high. As it turned out, the repair worked so well that I didn't bother to measure the plate voltage of the 7C7 post-repair. I probably could have used 10K or even 5K. Maybe I'll pull it back out of the cabinet and measure the 7C7 plate voltage later on.
And since I had some 250 pF caps on hand but no 200 pF caps, 250 pF is what I used.
--
Ron Ramirez
Ferdinand IN
