Hi Jim, great video. You are absolutely correct, all radios are fixable if we take time to replace bad parts and make sure connect wires to correct connections 😂. I had that experience several times when working late at night and takes days trying to find the mistake that I made. Lately I walk away from the project when get tired 😂. Have a great day Jim. Regards, Jay
Well you asked for guesses so I will try... The frequency of the osc is a function of Inductance and Capacitance. So the issue is just between those items. f=1/(2 x pi x (sqrt of L x C)), not that that helps, but it shows that L and C are all that matter. C is variable all over the place including replaced caps. (Gurus tell us all the time that caps in the RF section that are mica can be handpicked to fix tracking errors, not that I suspect that.) But there is also some capacitance in the tube, (You may want to try a substitute 6SA7 for fun.) So, what else changed? a wiring mistake on the posts of the Osc coil (the L in the formula)? Remember that some old style mechanical drawings show the end versus side view different from what has been common over the last 50 years (first angle projection vs third angle projection today). If the drawing is first angle projection, you may have incorrect posts on the coil connected if you are a third angle guy like me. It may be an issue with posts C, D and/or F? Should be able to look closely at the side view and wiring on the coil sketch to verify. Anyway I know you went over all that, but if you handed it to me as a test, those are what I'd check first. Best of luck Jim!
Frequency ( f in Hertz) you want is equal to 1/ (2x pi x R x C) . R is in Ohms ,C is in Farads. Since you know the frequency and resistance you have you can solve the C ( Farads for trimmer cap). Try C = 1/(2 x pi x f x R). Easier said than done. 😵💫
Hi Jim, great video. You are absolutely correct, all radios are fixable if we take time to replace bad parts and make sure connect wires to correct connections 😂. I had that experience several times when working late at night and takes days trying to find the mistake that I made. Lately I walk away from the project when get tired 😂. Have a great day Jim. Regards, Jay
Thanks for sharing Jim
Well you asked for guesses so I will try...
The frequency of the osc is a function of Inductance and Capacitance. So the issue is just between those items. f=1/(2 x pi x (sqrt of L x C)), not that that helps, but it shows that L and C are all that matter. C is variable all over the place including replaced caps. (Gurus tell us all the time that caps in the RF section that are mica can be handpicked to fix tracking errors, not that I suspect that.) But there is also some capacitance in the tube, (You may want to try a substitute 6SA7 for fun.)
So, what else changed? a wiring mistake on the posts of the Osc coil (the L in the formula)? Remember that some old style mechanical drawings show the end versus side view different from what has been common over the last 50 years (first angle projection vs third angle projection today). If the drawing is first angle projection, you may have incorrect posts on the coil connected if you are a third angle guy like me. It may be an issue with posts C, D and/or F? Should be able to look closely at the side view and wiring on the coil sketch to verify. Anyway I know you went over all that, but if you handed it to me as a test, those are what I'd check first. Best of luck Jim!
Frequency ( f in Hertz) you want is equal to 1/ (2x pi x R x C) . R is in Ohms ,C is in Farads. Since you know the frequency
and resistance you have you can solve the C ( Farads for trimmer cap). Try C = 1/(2 x pi x f x R). Easier said than done. 😵💫