01-21-2024, 04:31 PM
restoring this portable radio D664
Before restoration turned it on and got lots of noise but no stations. Assumed eletrolytics were bad as well as old selenium rectifier since it only put out 107 volts not 125 as shown on schemo . Also replaced paper capacitors, and c4 , 3 and 7 . All tubes tested and Okay. tested all resisters and okay. Same issue and voltage at diode not any higher. While all tubes were good at startup noticed that IU4 was glowing brightly , so tested all tubes IU4 and IU5 are now NG . Before replacing tubes powered up without them .Only got 9 V dc at Diode output but -151 V DC at pin 1 on IU4 .Also noticed same voltage on the socket tab that connects to the IU4 heat shield . Any suggestions helpful
Before restoration turned it on and got lots of noise but no stations. Assumed eletrolytics were bad as well as old selenium rectifier since it only put out 107 volts not 125 as shown on schemo . Also replaced paper capacitors, and c4 , 3 and 7 . All tubes tested and Okay. tested all resisters and okay. Same issue and voltage at diode not any higher. While all tubes were good at startup noticed that IU4 was glowing brightly , so tested all tubes IU4 and IU5 are now NG . Before replacing tubes powered up without them .Only got 9 V dc at Diode output but -151 V DC at pin 1 on IU4 .Also noticed same voltage on the socket tab that connects to the IU4 heat shield . Any suggestions helpful