05-11-2026, 11:13 PM
Hi Gliphmon,
Try replacing the resistor. With no load, the value at pin 4 of either socket should be very close to the B+ value at the other side of R4. Also make sure that the resistors that replaced the "Voltage divider are in the correct order. The Order s from the junction of the field coil, output transformer and c32, the resistors should be 3500 Ohms (R14), 13KOhm (R15) 85 Ohm (R16), chassis ground, 40 Ohm (R17), 175 Ohm (R18), HV Sec center tap.
You can use a DPDT switch to switch the audio between the external input and screw 1 of the phono terminal strip. The other pole of the switch can be set to short screw 1 to screw 3, shorting the output of the detector to ground.
Regarding shutting off the heaters, don't. There is a theory that putting B+ on tubes with the heaters off can shorten the tube life. I believe that running the filaments with no B+ is not only harmless but can rejuvenate the tube. Guitar amps and other high power industrial amps had an on/standby switch that would switch on or off the B+. The idea was to not turn the B+ on until after the tubes were heating for at least 30 seconds. In fact rectifier tubes were often designed to have a "controlled warmup to allow the other tubes to warm up before B+ was available. Many color sets of the 70s and 80s were mostly solid state had a small transformer for the CRT to keep the heater on. This was not just for "instant picture, the concept was that applying all the B voltages. especially the high voltage before the heaters were up to temp stripped the cathode and affected the emission of one or more guns. I have seen several color CRTs on sets without this feature, where one of the guns was dead, so a primary color was missing. This was rare on newer CRTs, possibly due to this feature, possibly due to better materials / manufacturing tevchniques. TV Man can chime in as he was a pro.
Try replacing the resistor. With no load, the value at pin 4 of either socket should be very close to the B+ value at the other side of R4. Also make sure that the resistors that replaced the "Voltage divider are in the correct order. The Order s from the junction of the field coil, output transformer and c32, the resistors should be 3500 Ohms (R14), 13KOhm (R15) 85 Ohm (R16), chassis ground, 40 Ohm (R17), 175 Ohm (R18), HV Sec center tap.
You can use a DPDT switch to switch the audio between the external input and screw 1 of the phono terminal strip. The other pole of the switch can be set to short screw 1 to screw 3, shorting the output of the detector to ground.
Regarding shutting off the heaters, don't. There is a theory that putting B+ on tubes with the heaters off can shorten the tube life. I believe that running the filaments with no B+ is not only harmless but can rejuvenate the tube. Guitar amps and other high power industrial amps had an on/standby switch that would switch on or off the B+. The idea was to not turn the B+ on until after the tubes were heating for at least 30 seconds. In fact rectifier tubes were often designed to have a "controlled warmup to allow the other tubes to warm up before B+ was available. Many color sets of the 70s and 80s were mostly solid state had a small transformer for the CRT to keep the heater on. This was not just for "instant picture, the concept was that applying all the B voltages. especially the high voltage before the heaters were up to temp stripped the cathode and affected the emission of one or more guns. I have seen several color CRTs on sets without this feature, where one of the guns was dead, so a primary color was missing. This was rare on newer CRTs, possibly due to this feature, possibly due to better materials / manufacturing tevchniques. TV Man can chime in as he was a pro.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis
Best Regards,
MrFixr55




