11 hours ago
Hi Tim,
Nice job! Was that a broken cold joint on one of those resistors by the transformer in one of those pics? Weah, the hum bar is puzzling. You state that it does not occur on the upper channels. Does it occur on the lower channels without a signal? Most NTSC RF Modulators allow a choice only between ch3 and 4. Does your RF Modulator allow selection of other frequencies? Does it hum on Ch 5 and 6, but not 7 and higher? Is there noise in the sound also?
Do you have an ATSC to NTSC convertor or AV jacks on the back of your cable box? (Mine has both HDMI and NTSC outputs.)
My experience with PS induced hum (from bad filters) in TVs was a slowly moving bar, or in some cases, slowly moving distortion in both horizontal and vertical planes.
PS- Mullard HiFi tubes are preferred to almost anything other than Telefunken, but I think that the holy grail tubes are Mullard or Telefunken 12AX7s as they are used extensively in classic HiFi and Guitar amps. 12AU7s and especially 12AT7s are not as popular in Audio circuits.
Nice job! Was that a broken cold joint on one of those resistors by the transformer in one of those pics? Weah, the hum bar is puzzling. You state that it does not occur on the upper channels. Does it occur on the lower channels without a signal? Most NTSC RF Modulators allow a choice only between ch3 and 4. Does your RF Modulator allow selection of other frequencies? Does it hum on Ch 5 and 6, but not 7 and higher? Is there noise in the sound also?
Do you have an ATSC to NTSC convertor or AV jacks on the back of your cable box? (Mine has both HDMI and NTSC outputs.)
My experience with PS induced hum (from bad filters) in TVs was a slowly moving bar, or in some cases, slowly moving distortion in both horizontal and vertical planes.
PS- Mullard HiFi tubes are preferred to almost anything other than Telefunken, but I think that the holy grail tubes are Mullard or Telefunken 12AX7s as they are used extensively in classic HiFi and Guitar amps. 12AU7s and especially 12AT7s are not as popular in Audio circuits.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis
Best Regards,
MrFixr55