1948 radio lamp

12/27/2007 11:34:30 AMjohn g

I need a schematic for this 1948 radio lamp. It uses these tubes: 35Z5, 12A8, 12K7, 12Q7, and a 35L6. Can't get any stations and I think the osc is not running but I don't know why yet. Would this be in a Sams and, if so, what number?

12/27/2007 2:16:40 PMNorm Leal

John

The circuit will be in Rider which is available above under Resources. You need the model number in order to get an exact schematic.

12A8 is the oscillator tube. Check voltages on this tube and continuity of the oscillator coil.

Norm

:I need a schematic for this 1948 radio lamp. It uses these tubes: 35Z5, 12A8, 12K7, 12Q7, and a 35L6. Can't get any stations and I think the osc is not running but I don't know why yet. Would this be in a Sams and, if so, what number?

12/27/2007 7:59:56 PMjohn g

I seem to have proper voltages and continuity but the tuning condenser shows 0 ohms to ground on both sets of plates for the back variable condenser. The fixed set shows 0 to ground but I can't see why or what could be the path.

:John
:
: The circuit will be in Rider which is available above under Resources. You need the model number in order to get an exact schematic.
:
: 12A8 is the oscillator tube. Check voltages on this tube and continuity of the oscillator coil.
:
:Norm
:
::I need a schematic for this 1948 radio lamp. It uses these tubes: 35Z5, 12A8, 12K7, 12Q7, and a 35L6. Can't get any stations and I think the osc is not running but I don't know why yet. Would this be in a Sams and, if so, what number?

12/27/2007 8:50:46 PMDoug Criner

John: There is usually a coil in parallel with the tuning caps. The coil needs to be disconnected when measuring resistance to see if the tuning caps are shorted.
Doug

:I seem to have proper voltages and continuity but the tuning condenser shows 0 ohms to ground on both sets of plates for the back variable condenser. The fixed set shows 0 to ground but I can't see why or what could be the path.
:
:
::John
::
:: The circuit will be in Rider which is available above under Resources. You need the model number in order to get an exact schematic.
::
:: 12A8 is the oscillator tube. Check voltages on this tube and continuity of the oscillator coil.
::
::Norm
::
:::I need a schematic for this 1948 radio lamp. It uses these tubes: 35Z5, 12A8, 12K7, 12Q7, and a 35L6. Can't get any stations and I think the osc is not running but I don't know why yet. Would this be in a Sams and, if so, what number?

12/27/2007 9:06:38 PMJohn

Thanks All, I found what was wrong. My tuning condenser was showing a short off both plates when out of the radio completely and could see nothing touching to ground the stationary plates so guessed it could be a burr under the mica on the trimmer. Loosened the screw up and cleaned a little and then put the screw back and no short. Reinstalled in the radio and it now works. Hey!

:John: There is usually a coil in parallel with the tuning caps. The coil needs to be disconnected when measuring resistance to see if the tuning caps are shorted.
:Doug
:
::I seem to have proper voltages and continuity but the tuning condenser shows 0 ohms to ground on both sets of plates for the back variable condenser. The fixed set shows 0 to ground but I can't see why or what could be the path.
::
::
:::John
:::
::: The circuit will be in Rider which is available above under Resources. You need the model number in order to get an exact schematic.
:::
::: 12A8 is the oscillator tube. Check voltages on this tube and continuity of the oscillator coil.
:::
:::Norm
:::
::::I need a schematic for this 1948 radio lamp. It uses these tubes: 35Z5, 12A8, 12K7, 12Q7, and a 35L6. Can't get any stations and I think the osc is not running but I don't know why yet. Would this be in a Sams and, if so, what number?