01-06-2018, 05:36 PM
When troubleshooting a radio, I work from the audio section back to the IF stages, then osc, and RF last.
A couple of things I see here. First you need to verify the audio section is working properly. You can turn the volume up and put you finger or a screwdriver on the wiper. You should hear a loud hum. If not, you need to fix the audio section. The voltages look right, but maybe you have a bad speaker. I have seen them open up. Your speaker is on the top so it's prone to all kinds of things getting into it.
If audio section is good, check the radio/phono switch. If intermittent or open you might get enough audio to bleed through causing your symptom.
What looks bad is the screen voltages being too high around the IF amps, almost source voltage. The tubes are not drawing enough current. I had one of these sets about 35 years ago with the same symptoms and it was a bad IF transformer. No SMD just an open winding. I would check all IF coils for being open. Since you had them out, anything is possible.
If you are not certain about the oscillator, grab another radio and tune it to approximately 1.445. Then tune the S53 back and forth around 1.0 on the BC band. If working, you will hear the other radio get quiet and then noisy as you tune the S53 back and forth. I'm guessing hi side injection, so the S53 osc would be 455KHz above the dial freq. if this is not working, then troubleshooting the osc coils and band switch are in order.
A signal generator is great for this as you can inject the IF frequency and you should hear it loud and clear in the speaker. If good you work back to the front end of the radio. Also, do test and or substitute tubes.
A couple of things I see here. First you need to verify the audio section is working properly. You can turn the volume up and put you finger or a screwdriver on the wiper. You should hear a loud hum. If not, you need to fix the audio section. The voltages look right, but maybe you have a bad speaker. I have seen them open up. Your speaker is on the top so it's prone to all kinds of things getting into it.
If audio section is good, check the radio/phono switch. If intermittent or open you might get enough audio to bleed through causing your symptom.
What looks bad is the screen voltages being too high around the IF amps, almost source voltage. The tubes are not drawing enough current. I had one of these sets about 35 years ago with the same symptoms and it was a bad IF transformer. No SMD just an open winding. I would check all IF coils for being open. Since you had them out, anything is possible.
If you are not certain about the oscillator, grab another radio and tune it to approximately 1.445. Then tune the S53 back and forth around 1.0 on the BC band. If working, you will hear the other radio get quiet and then noisy as you tune the S53 back and forth. I'm guessing hi side injection, so the S53 osc would be 455KHz above the dial freq. if this is not working, then troubleshooting the osc coils and band switch are in order.
A signal generator is great for this as you can inject the IF frequency and you should hear it loud and clear in the speaker. If good you work back to the front end of the radio. Also, do test and or substitute tubes.
