06-20-2021, 12:38 AM
Hi everyone,
Well good news! The 1934 Model 680 Hudson set built by Zenith is now going.I would like to say that this was due to a rigorous and disciplined working through of the various sections informed by a deep and instinctive grasp of radio theory until the set burst into life.I would like to say that. Certainly I discovered early on that the buffer cap across the 6Z4's anodes was a dead short. There was a smoothing cap missing off the H.T. line.The H.T. was only 89 volts until I reinstalled the original Zenith vibrator when the H.T. lifted to 158 volts.Lots of the caps have now been replaced.Thanks to Joe's work pointing me toward the right Rider volume and then armed with the schematic I was able to reattach the loose wire from the top of the volume control with confidence.To be fair, when working blind I had a strong hunch as to which tag it should go to .The schematic confirmed this.But the set still did not go.
So ,as you do , I fell to musing and pondering and poking , disconsolate , with the prodding hook I use to trace wires.The signal tracer had shown that signal was appearing at the top cap (control grid) of the 6C6 mixer but not at the top cap of the 6D6 i.f. amp.So I was prodding around the 6C6 socket when , you guessed it. I'm still not sure what short I had disturbed but I suspect something round the cap and resistor (grid leak ?) between the osc coil and the cathode of the 6C6 which would suggest the autodyne was not "dyning" so that no signal was appearing at the grid of the I.F. amp. Sound feasible? Any way it now goes.Time for rejoicing. Thanks especially to Joe for his help. So I now have two vintage Hudson radios though neither has the flexible cables or tuning head ! Or indeed a Hudson to install them in!Thanks, Mike!
This raises a question though, about oscillator testing. With a 6A7 or a 6K8 or similar I usually look for a small negative voltage on the grid of the oscillator triode to tell me if the oscillator is working.How do you test an autodyne to see if the oscillator function is operating? i have been offered a technique by a colleague here in N.Z. but I am not confident using it. Do Philco Phorum members have any suggestions about this. Thanks everyone and cheers
Well good news! The 1934 Model 680 Hudson set built by Zenith is now going.I would like to say that this was due to a rigorous and disciplined working through of the various sections informed by a deep and instinctive grasp of radio theory until the set burst into life.I would like to say that. Certainly I discovered early on that the buffer cap across the 6Z4's anodes was a dead short. There was a smoothing cap missing off the H.T. line.The H.T. was only 89 volts until I reinstalled the original Zenith vibrator when the H.T. lifted to 158 volts.Lots of the caps have now been replaced.Thanks to Joe's work pointing me toward the right Rider volume and then armed with the schematic I was able to reattach the loose wire from the top of the volume control with confidence.To be fair, when working blind I had a strong hunch as to which tag it should go to .The schematic confirmed this.But the set still did not go.
So ,as you do , I fell to musing and pondering and poking , disconsolate , with the prodding hook I use to trace wires.The signal tracer had shown that signal was appearing at the top cap (control grid) of the 6C6 mixer but not at the top cap of the 6D6 i.f. amp.So I was prodding around the 6C6 socket when , you guessed it. I'm still not sure what short I had disturbed but I suspect something round the cap and resistor (grid leak ?) between the osc coil and the cathode of the 6C6 which would suggest the autodyne was not "dyning" so that no signal was appearing at the grid of the I.F. amp. Sound feasible? Any way it now goes.Time for rejoicing. Thanks especially to Joe for his help. So I now have two vintage Hudson radios though neither has the flexible cables or tuning head ! Or indeed a Hudson to install them in!Thanks, Mike!
This raises a question though, about oscillator testing. With a 6A7 or a 6K8 or similar I usually look for a small negative voltage on the grid of the oscillator triode to tell me if the oscillator is working.How do you test an autodyne to see if the oscillator function is operating? i have been offered a technique by a colleague here in N.Z. but I am not confident using it. Do Philco Phorum members have any suggestions about this. Thanks everyone and cheers
