Two Northern Electric Baby Champ Tube Radios Video #2 - Output Tube Grid Blocking Capacitors

[@randomsteve4288]

40:46 The grid coupling cap C21(10nF/50nF) forms a high pass RC filter along with the grid resistor R7 (470k). The -3db point for C21= 0,01uF is ~34 Hz. With C21=0,05uF it is ~7Hz. To put this into perspective; Standard AM radio is limited to 40Hz to 5kHz bandwith. Typical console AM radios only reproduce 100Hz to 4kHz of that. And midget size AM radios only 200Hz to 3kHz. So judge for urself if dropping the -3dB point in the grid coupling high pass filter from 34Hz to 7Hz will have any influence...

[@glennrechnitzer8704]

WOW Just change all the capacitors especially the filter capacitors.

[@randomsteve4288]

It is typical for Jim to hold a several minute long memorial service for any bad leaky cap he replaces. Which is understandable since the 50 cents a new cap costs and the 2 minute labor to change would push repair costs through the roof if you just replaced all leaky caps. The best repairs are those, which just fix the major issues and leave enough issues unresolved for future, not warranty related comebacks. So Jim refusing to replace all leaky caps is a win-win,- for him of course, since the poor owner will never know that future trouble with leaky caps could and should have been avoided by going that extra mile on the first repair.

[@Rebel9668]

It's not a restoration, just a repair. Back in the day if you took your radio or tv in for service, they would repair it by replacing what was causing the issue, not replace everything in it.

[@Rebel9668]

I like a very slight hum. Lets me know when I've accidently left something on, lol.

[@randomsteve4288]

44:49 Dear Mr Lindenas. If you cannot imagine or comprehend how a leaky grid coupling capacitor will both pull the grid voltage high and simultaneously the plate voltage of the previous tube low, you should seriously reconsider working on tube radios. And it shows that the "lecturing" on your videos regarding the importance of grid coupling caps is nothing but a parrot repeating something he heard without actually understanding it.