i am restoring this chassis and the rfchoke is missing.would another one work from another zenith or does it have to be from 9s262

This is a special tapped choke designed to block two frequency ranges, as selected by the bandswitch. All this choke does is block RF from getting onto the B+ bus and causing problems elsewhere in the set- a bypass cap and resistor will accomplish the same thing, though at the cost of a little plate voltage and stage gain, which probably won't be missed.

:This is a special tapped choke designed to block two frequency ranges, as selected by the bandswitch. All this choke does is block RF from getting onto the B+ bus and causing problems elsewhere in the set- a bypass cap and resistor will accomplish the same thing, though at the cost of a little plate voltage and stage gain, which probably won't be missed.
:you are talking to a beginner,what size cap and resistor.and where will it hook up.

I think that I would use a 1.2K ohm 0.5 watt resistor installed across the two extreme ends of the present choke- that is, from the detector transformer primary to the B+ bus (line that runs back to C21, toward the right side of the schematic).

Assuming that the RF amp tube (6K7) plate draws about 15 mA or less, and that B+ is around 250 volts, inserting the 1.2K resistor will cause a voltage drop across it of 18 volts (V=IR). This isn't enough to seriously degrade operation of this stage.

The resistor wattage needs to be 0.5 watt. P=IV; so 0.015 x 18 = 0.27 watts. Too big for a quarter watt; so must uprate it to 0.5 watts.

Completely remove the bad choke from the radio. Snip the tap wires running from it to the bandswitch at the bandswitch terminals. Then install the resistor.

Now, attach one end of a 0.1 microfarad cap (600V) to the detector transformer primary-1.2K resistor junction. Solder the other end of the cap to a nearby chassis ground.

You should now have a working RF amp stage (a bad RF choke would result in no plate voltage to the RF amp tube). RF that appears at the "hot" side of the detector transformer will be shunted to ground via the capacitor before it can make it onto the B+ bus.

Before you do any of this, you might check the continuity of the detector primary transformer and verify (again) that the RF choke is really open.

:I think that I would use a 1.2K ohm 0.5 watt resistor installed across the two extreme ends of the present choke- that is, from the detector transformer primary to the B+ bus (line that runs back to C21, toward the right side of the schematic).
:
:Assuming that the RF amp tube (6K7) plate draws about 15 mA or less, and that B+ is around 250 volts, inserting the 1.2K resistor will cause a voltage drop across it of 18 volts (V=IR). This isn't enough to seriously degrade operation of this stage.
:
:The resistor wattage needs to be 0.5 watt. P=IV; so 0.015 x 18 = 0.27 watts. Too big for a quarter watt; so must uprate it to 0.5 watts.
:
:Completely remove the bad choke from the radio. Snip the tap wires running from it to the bandswitch at the bandswitch terminals. Then install the resistor.
:
:Now, attach one end of a 0.1 microfarad cap (600V) to the detector transformer primary-1.2K resistor junction. Solder the other end of the cap to a nearby chassis ground.
:
:You should now have a working RF amp stage (a bad RF choke would result in no plate voltage to the RF amp tube). RF that appears at the "hot" side of the detector transformer will be shunted to ground via the capacitor before it can make it onto the B+ bus.
:
:Before you do any of this, you might check the continuity of the detector primary transformer and verify (again) that the RF choke is really open.
:
:there is no rfchoke in the set it is missing.i will try and figure out what you have said.i am still learning,might have more questions,sorry.

::I think that I would use a 1.2K ohm 0.5 watt resistor installed across the two extreme ends of the present choke- that is, from the detector transformer primary to the B+ bus (line that runs back to C21, toward the right side of the schematic).
::
::Assuming that the RF amp tube (6K7) plate draws about 15 mA or less, and that B+ is around 250 volts, inserting the 1.2K resistor will cause a voltage drop across it of 18 volts (V=IR). This isn't enough to seriously degrade operation of this stage.
::
::The resistor wattage needs to be 0.5 watt. P=IV; so 0.015 x 18 = 0.27 watts. Too big for a quarter watt; so must uprate it to 0.5 watts.
::
::Completely remove the bad choke from the radio. Snip the tap wires running from it to the bandswitch at the bandswitch terminals. Then install the resistor.
::
::Now, attach one end of a 0.1 microfarad cap (600V) to the detector transformer primary-1.2K resistor junction. Solder the other end of the cap to a nearby chassis ground.
::
::You should now have a working RF amp stage (a bad RF choke would result in no plate voltage to the RF amp tube). RF that appears at the "hot" side of the detector transformer will be shunted to ground via the capacitor before it can make it onto the B+ bus.
::
::Before you do any of this, you might check the continuity of the detector primary transformer and verify (again) that the RF choke is really open.
::
::there is no rfchoke in the set it is missing.i will try and figure out what you have said.i am still learning,might have more questions,sorry.
:the best i can tell .you are saying to install the resistor on the band switch ,where the det.wire is mounted and where the eye tube wire is connected.then the cap is installed where the eye tube wire is connected and chassis ground.all of these connections are on the band switch.
:

::the best i can tell .you are saying to install the resistor on the band switch ,where the det.wire is mounted and where the eye tube wire is connected.then the cap is installed where the eye tube wire is connected and chassis ground.all of these connections are on the band switch.
::
:
No. Capacitor is on the detector transformer side of the resistor. What you call the "eye tube side" is B+ (trace it back to C21). Resistor goes between the B+ line going to the eye tube and the detector transformer primary.

Recommend not connecting anything to the bandswitch to avoid confusion. But t's OK to use the B+ wire that is connected there as a tie point for the resistor if the other wires that used to go to the tapped choke (and one capacitor) are disconnected.

: ::the best i can tell .you are saying to install the resistor on the band switch ,where the det.wire is mounted and where the eye tube wire is connected.then the cap is installed where the eye tube wire is connected and chassis ground.all of these connections are on the band switch.
:::
::
:No. Capacitor is on the detector transformer side of the resistor. What you call the "eye tube side" is B+ (trace it back to C21). Resistor goes between the B+ line going to the eye tube and the detector transformer primary.
:
:Recommend not connecting anything to the bandswitch to avoid confusion. But t's OK to use the B+ wire that is connected there as a tie point for the resistor if the other wires that used to go to the tapped choke (and one capacitor) are disconnected.
:thank you for your help.the radio and shortwave are working great.could not have done it with out your help.thanks very much.

CV,
Not sure why a tapped choke is being used. I assume the bandswitch is in BC position. If that is the case then there is a 25pf cap across the total of the choke making it a tuned circuit of sorts?

Clifton

:I think that I would use a 1.2K ohm 0.5 watt resistor installed across the two extreme ends of the present choke- that is, from the detector transformer primary to the B+ bus (line that runs back to C21, toward the right side of the schematic).
:
:Assuming that the RF amp tube (6K7) plate draws about 15 mA or less, and that B+ is around 250 volts, inserting the 1.2K resistor will cause a voltage drop across it of 18 volts (V=IR). This isn't enough to seriously degrade operation of this stage.
:
:The resistor wattage needs to be 0.5 watt. P=IV; so 0.015 x 18 = 0.27 watts. Too big for a quarter watt; so must uprate it to 0.5 watts.
:
:Completely remove the bad choke from the radio. Snip the tap wires running from it to the bandswitch at the bandswitch terminals. Then install the resistor.
:
:Now, attach one end of a 0.1 microfarad cap (600V) to the detector transformer primary-1.2K resistor junction. Solder the other end of the cap to a nearby chassis ground.
:
:You should now have a working RF amp stage (a bad RF choke would result in no plate voltage to the RF amp tube). RF that appears at the "hot" side of the detector transformer will be shunted to ground via the capacitor before it can make it onto the B+ bus.
:
:Before you do any of this, you might check the continuity of the detector primary transformer and verify (again) that the RF choke is really open.
:
:

My guess is that it is intended to filter out RF artifacts around the IF frequency. This isn't of any use these days since there are no powerful coastal beacons operating in that range since GPS nav has become nearly universal.

CV,

My guess was leaning toward the same thing. Still not certain why the tapped choke or why the parallel combination is not adjustable. Just a guess, but I think the choke may have been fairly large possibly a value of around 5mH?

Clifton

:My guess is that it is intended to filter out RF artifacts around the IF frequency. This isn't of any use these days since there are no powerful coastal beacons operating in that range since GPS nav has become nearly universal.
: