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42-327 heater circuit confusion
#24

Hi SlidesK,

Follow Morzh's advice, visually trace the wiring and draw a schematic of what you see. Remember, for all tubes except the 50L6, the heater connections are pins 1 and 8. This includes the 35Z3. For the 50L6, the heaters are on pins 2 and 7. I verified this for each tube in your set against the RCA receiving tube manual, Rev RC13, published 1940 (or so)

The pictorial of the underside chassis layout is for the Code 121 set with the 35Z5 rectifier.  If I am right, sets with the 35Z3 will not have the Candohm 80 Ohm resistor.

Are you using the dimbulb tester when you are making the voltage measurements for the heaters?  If so, the heater voltages will be low because there will be a drop across the dim bulb. 

The way the Code 122 set is supposed to be wired, there is no resistor in the heater string, therefore, there should be 35V across the 35Z3 heater, 50V across the 50L6 12V across the XXD and 6V across the rest of the tubes for a designed line input of 115V.  You should actually see a little higher as most power is about 120V these days.

Check across the power line between Pins 1,2 of the 35Z3 and the power switch.  Chack both sides of the switch to determine if there is a voltage drop across the switch.  There should not be.  If you receive 115-125V there but are having these low heater voltage readings, then something is wrong.  You may have a bad connection somewhere, but by this time, you should be hearing something from the radio.

Good luck and keep posting.  You will get this going!!

"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis

Best Regards, 

MrFixr55


Messages In This Thread
42-327 heater circuit confusion - by SlidesK - 01-21-2026, 12:31 PM
RE: 42-327 heater circuit confusion - by morzh - 01-21-2026, 05:31 PM
RE: 42-327 heater circuit confusion - by SlidesK - 01-21-2026, 06:53 PM
RE: 42-327 heater circuit confusion - by SlidesK - 01-21-2026, 07:09 PM
RE: 42-327 heater circuit confusion - by Arran - 01-21-2026, 10:50 PM
RE: 42-327 heater circuit confusion - by morzh - 01-21-2026, 11:16 PM
RE: 42-327 heater circuit confusion - by Arran - 01-22-2026, 01:25 AM
RE: 42-327 heater circuit confusion - by SlidesK - 01-22-2026, 07:02 AM
RE: 42-327 heater circuit confusion - by MrFixr55 - 01-22-2026, 07:10 AM
RE: 42-327 heater circuit confusion - by morzh - 01-22-2026, 10:00 AM
RE: 42-327 heater circuit confusion - by SlidesK - 01-22-2026, 10:34 AM
RE: 42-327 heater circuit confusion - by morzh - 01-22-2026, 10:40 AM
RE: 42-327 heater circuit confusion - by MrFixr55 - 01-22-2026, 11:19 AM
RE: 42-327 heater circuit confusion - by Arran - 01-23-2026, 01:40 AM
RE: 42-327 heater circuit confusion - by MrFixr55 - 01-23-2026, 07:41 AM
RE: 42-327 heater circuit confusion - by SlidesK - 01-23-2026, 06:25 PM
RE: 42-327 heater circuit confusion - by RodB - 01-23-2026, 09:00 PM
RE: 42-327 heater circuit confusion - by SlidesK - 01-23-2026, 09:46 PM
RE: 42-327 heater circuit confusion - by morzh - 01-23-2026, 10:07 PM
RE: 42-327 heater circuit confusion - by SlidesK - 01-23-2026, 10:34 PM
RE: 42-327 heater circuit confusion - by Arran - 01-23-2026, 10:56 PM
RE: 42-327 heater circuit confusion - by morzh - 01-23-2026, 11:27 PM
RE: 42-327 heater circuit confusion - by MrFixr55 - 01-23-2026, 11:58 PM
RE: 42-327 heater circuit confusion - by morzh - 01-24-2026, 02:39 PM
RE: 42-327 heater circuit confusion - by SlidesK - 01-26-2026, 06:09 AM
RE: 42-327 heater circuit confusion - by MrFixr55 - 01-26-2026, 10:45 AM
RE: 42-327 heater circuit confusion - by SlidesK - 01-26-2026, 12:50 PM
RE: 42-327 heater circuit confusion - by MrFixr55 - 01-26-2026, 03:01 PM
RE: 42-327 heater circuit confusion - by SlidesK - 01-26-2026, 03:24 PM
RE: 42-327 heater circuit confusion - by SlidesK - 01-26-2026, 04:28 PM
RE: 42-327 heater circuit confusion - by SlidesK - 01-27-2026, 08:52 AM
RE: 42-327 heater circuit confusion - by morzh - 01-27-2026, 10:08 AM
RE: 42-327 heater circuit confusion - by SlidesK - 01-27-2026, 11:05 AM
RE: 42-327 heater circuit confusion - by morzh - 01-27-2026, 11:19 AM
RE: 42-327 heater circuit confusion - by SlidesK - 01-27-2026, 11:30 AM
RE: 42-327 heater circuit confusion - by SlidesK - 01-31-2026, 01:54 PM
RE: 42-327 heater circuit confusion - by SlidesK - 02-04-2026, 05:32 PM
RE: 42-327 heater circuit confusion - by MrFixr55 - 02-05-2026, 08:46 AM
RE: 42-327 heater circuit confusion - by SlidesK - 02-05-2026, 10:47 AM



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