Check the off/on switch first,. If it's ok, check the tubes for a burned out filament. The tube filaments are all in series. If one is burned out, none will light (heat). Pull each tube and check for heater continuity with an ohm meter.
http://www.nostalgiaair.org/PagesByModel/077/M0015077.pdf
Tested the switch in all positions? Are you talking about the on-off switch on the volume control or the band selector switch that has three positions? You need to connect your meter to the AC line cord and short the power switch on the back of the volume control to check the power switch.
Lewis
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:Tested the switch in all positions? Are you talking about the on-off switch on the volume control or the band selector switch that has three positions? You need to connect your meter to the AC line cord and short the power switch on the back of the volume control to check the power switch.
:Lewis
I think his confusion is on the number of terminals on the switch. With a few of the RCA's I have, there may be an extra terminal on the rear of the switch that isn't electrically connected to the switch, but serves as a junction point for other wiring. Nevertheless though, even if the switch is bad, you should have continuity between one of the plug prongs and one of the connections on the switch. If you don't, your line cord may be bad. Hope that helps.
Well what’s it gonna’ turn out to be ?. . . . bad power plug / connection-----bad /intermittently open AC line cord-----bad power /on/off switch---Bad tube(s)-----bad tube socket / contact-----cold solder joint(s)--- an open in the daisy chained, inter connective wiring.
An initial test would be to take an ohmmeter in hand and short its leads to confirm its initial proper action and then flip the power switch in its ON position and then connect the ohmmeter leads across the AC power plug prongs and see if a low hundred or so of ohms reading is present.
If not, move the ohmmeter negative lead to the chassis proper and be sure that it makes good low ohmic electrical contact and then try connecting the other ohmmeter lead to one and then the other AC line prong to see if a VEWY low ohms reading is present. . . .that would be represented by the trouble shooting path of the (GREEN) buss as is shown on the accompanying thumbnail Schema.
If no low ohms reading is present , then do the [1]-[2]-[3] test with one ohmmeter lead being referenced to chassis ground. If it passes only the the [1]-[2] test, then, concentrate on the line cord and plug.
You see, it just could have been that Aunt Tillie had previously been moving the radio from atop the ice box, over near the bread making table and carried it out to the milking barn. . .every day. Now, after that four thousand, nine hundred and ‘eleventeenth trip, the line cord had been subjected to so much flexure at a certain bending point, that the wire had finally fatigued and opened most. . .and then. . . that final. . . . copper wire strand internal within the insulative covering.
Sooooo, be sure to flex---compress---that wire near the radio proper and at its other extreme, near the AC power plug when ohmming it out.
After that ground buss checks out, but the set still no workee, then , the next area would be the (MAGENTA) buss. In that case keep using the chassis ground referencing and this time walk initially to test reference [A] and hopefully, then you will be reading the cold resistance of a 12SQ7 filament, so take note of its resistance and walk the probe down to [B] where you should hopefully find about a like resistance being added to your ohms reading, with two like filaments then being in series. The procedure repeats itself also at [C] and [D] when moving down to [E] but, NOW, that 35L6 filament will add about three times the resistance that you were experienced being added by each of the mere 12V tubes that you were ohmming out.
When you next move up past the 35Z5 to its reference [F], the same addition of a like lump of resistance [35L6] should show up.
( with that overall value being just a wee bit less due to the pilot lamps shunting a portion of the 35Z5 filament) .
If you have found an intact string of tube filament resistances up to that [F] reference point, there is only that [F] to [G] circuit through the other wire of the AC line cord and its other pin on the AC power cord left, to be tested out in the same manner as the other lead was.
That is the sequential procedure, using an ohmmeter and with no AC power ever being connected to the set. A final option, if this should not reveal the culprit, would the VERY-VERY rare situation of a filament opening intermittently on power application.
In this case, one can connect two clip leads across the 2 filament pins af the tested tube, at its socket, and run them out to where each lead can be connected to the two leads of a meter, set in its AC voltage scale and set up for reading in excess of 125 volts AC.
That permits a hands off safety situation, then one powers up the set and looks for the tube filament that is opening up and will then display a full AC line voltage as the reading.
Individually, you then walk through all tubes filament connections doing this test.
Standing by for feedback. . . .if required. . . .
73's de Edd
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:Well what’s it gonna’ turn out to be ?. . . . bad power plug / connection-----bad /intermittently open AC line cord-----bad power /on/off switch---Bad tube(s)-----bad tube socket / contact-----cold solder joint(s)--- an open in the daisy chained, inter connective wiring.
:
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:An initial test would be to take an ohmmeter in hand and short its leads to confirm its initial proper action and then flip the power switch in its ON position and then connect the ohmmeter leads across the AC power plug prongs and see if a low hundred or so of ohms reading is present.
:
:If not, move the ohmmeter negative lead to the chassis proper and be sure that it makes good low ohmic electrical contact and then try connecting the other ohmmeter lead to one and then the other AC line prong to see if a VEWY low ohms reading is present. . . .that would be represented by the trouble shooting path of the (GREEN) buss as is shown on the accompanying thumbnail Schema.
:
:
:
:If no low ohms reading is present , then do the [1]-[2]-[3] test with one ohmmeter lead being referenced to chassis ground. If it passes only the the [1]-[2] test, then, concentrate on the line cord and plug.
:
:
:You see, it just could have been that Aunt Tillie had previously been moving the radio from atop the ice box, over near the bread making table and carried it out to the milking barn. . .every day. Now, after that four thousand, nine hundred and ‘eleventeenth trip, the line cord had been subjected to so much flexure at a certain bending point, that the wire had finally fatigued and opened most. . .and then. . . that final. . . . copper wire strand internal within the insulative covering.
:
:
:
:Sooooo, be sure to flex---compress---that wire near the radio proper and at its other extreme, near the AC power plug when ohmming it out.
:
:
:
:After that ground buss checks out, but the set still no workee, then , the next area would be the (MAGENTA) buss. In that case keep using the chassis ground referencing and this time walk initially to test reference [A] and hopefully, then you will be reading the cold resistance of a 12SQ7 filament, so take note of its resistance and walk the probe down to [B] where you should hopefully find about a like resistance being added to your ohms reading, with two like filaments then being in series. The procedure repeats itself also at [C] and [D] when moving down to [E] but, NOW, that 35L6 filament will add about three times the resistance that you were experienced being added by each of the mere 12V tubes that you were ohmming out.
:
:When you next move up past the 35Z5 to its reference [F], the same addition of a like lump of resistance [35L6] should show up.
:( with that overall value being just a wee bit less due to the pilot lamps shunting a portion of the 35Z5 filament) .
:
:If you have found an intact string of tube filament resistances up to that [F] reference point, there is only that [F] to [G] circuit through the other wire of the AC line cord and its other pin on the AC power cord left, to be tested out in the same manner as the other lead was.
:
:
:
:That is the sequential procedure, using an ohmmeter and with no AC power ever being connected to the set. A final option, if this should not reveal the culprit, would the VERY-VERY rare situation of a filament opening intermittently on power application.
:
:In this case, one can connect two clip leads across the 2 filament pins af the tested tube, at its socket, and run them out to where each lead can be connected to the two leads of a meter, set in its AC voltage scale and set up for reading in excess of 125 volts AC.
:
:
:That permits a hands off safety situation, then one powers up the set and looks for the tube filament that is opening up and will then display a full AC line voltage as the reading.
:Individually, you then walk through all tubes filament connections doing this test.
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:Standing by for feedback. . . .if required. . . .
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:73's de Edd
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Boy, what an education!! I'm glad I have a printer. I will gladly go through all the steps provided by all. I did install a new line cord before testing the radio as the old one looked real rough. I also tested the new cord's continuity and used the old light bulb routine to be sure. I keep an old lamp in the shop for that sole purpose. I only tested the off/on volume control switch as I figured if there was current on the power leg that it had to be available at one of the other poles to make a cicuit once the radio was turned to the on position and volume increase was initiated. I also fully tested all tubes with my tube tester, but it may be in error so I'll pursue all replies.