I am currently restoring a Radiola 55E Model C89 the radio came without a speaker. I have the schematics however it does not indicate the value of the field coil and audio output transformer could someone assist please.

Hi Gazzbo.

The field coil value for the 55E is 2000 ohms.

(Source: The Complete List of Radiola Recievers 1925 to 1938)

The specs for a 47 output valve in the Miniwatt Technical Data book is as follows:-

Plate & Screen: 250 volts. Grid Bias: -16.5 volts. Load Resistance: 7000 ohms.

I am rewiring an electromagnetic speaker (wires had been mouse infected) I take it the field coil is polorised so what would be the correct position of the wires from the coil, I have black and tan covered wires.

Never really had to worry about that, but I have a Philips 2462 on the bench that has a K8 electrodynamic speaker. The residual Magnetism in it, has south at the front.

Positive and negative are not marked on it but is likely not critical if there is no DC component.

If there was a need to establish this, where there is DC (HMV secondary in cathode circuit in some), or it is a permanent magnet speaker, the polarity is correct when the cone jumps out; when DC is applied.

There are often four wires exiting the Bobin on an a electrodynamic two are the coil two are the "Humbuck" winding.

OK finally got to restoring Radiola 55E Model C89. The schematic is not exactly the same as the chassis. The problem is on the volume control it indicates the slider goes to ground and the connection goes through a total of 3 resistors R5 10K, R6 6.8K and R7 100 ohm. The only problem is R5 and R6 do not exist on my chassis, it only has (I presume R7). This is a wire wound resistor on a insulating former that the mice have eaten. Does anyone know the value of this resistor. I have tried to work it out measuring the resistance of one turn then multiplying it by the number of turns. I am not sure weather this is the correct method, it worked out to be around 450 ohms. Could somebody please assist me.

Here is the manual from Kevin Chant.

http://www.kevinchant.com/uploads/7/1/0/8/7108231/awa_service_data_(1932).pdf

I have looked at Kev's upload and the resistance of the resistors is not listed!
On my 55E they are from the 3K pot up, 80 ohm, 6.5k, and 11k.
Hope this helps,
Gary

That series of resistors is rather important The information that I have would suggest that the ones Gary has posted are the original values.

To get these values there may have to be a bit of paralleling & and eye kept on the wattage. If the pot is crook 3K is no longer a standard value & should be Wire wound. That configuration is not unusual for the era.

The volume is controlled principally by varing the self bias of the first three tubes; Which is the main reason values have importance. There are some traps in that circuit for young players.

Watch the resistor values on the 24 as it is a Plate detector & they distort if the parameters are not correct.

Marc