Delving into the Polle Royal Circa 1923 There is very little information about this rare vintage radio. I encourage readers to share any info that they find, e-mail me and I'll add your findings to the knowledge base.

Featured below is the schematic of my radio as I acquired it. A lot can happen over the course of nearly 90years, and I've seen many a radio modified by one or more of its owners. From an engineering standpoint, I have serious doubts about the placement of the 6 ohm filament rheostat in this first drawing. The type 01 tubes have 5 volt filaments, and a 6 volt rechargeable car battery was usually used as a filament supply. The filament rheostat served to reduce this voltage on a fresh battery, and then increase it as the battery wore down. Running the audio stage wide open would have served to shorten tube life as well as the time between battery charging. Charging the A battery often meant lugging the 30-50 lb battery to the local gas station for an overnight charge. . It is conceivable that this modification would have produced higher volume with lower distortion while allowing for volume and sensitivity control via the RF stages. The second schematic shows where I believe the rheostat was probably located originally.

A few notes about the design. The Polle Royal is a 5 tube TRF set using type 01 tubes throughout. The first two tubes are RF amplifiers, the third is a tuned detector which is followed by two audio stages. The final audio stage drives the coil of the headphones or speaker directly. More on this later. The power switch is incorporated into the speaker jack. Unplugging the speaker or headphone will disconnect the A and B battery from the circuit. The 6 ohm filament rheostat on my set also has an off position. With the filaments cold, no current will be drawn from the the A, B or C batteries. I don't know if my set has the original rheostat, but I have seen other sets use two methods of power control. The 200k rheostat controls the B+ voltage on the plates of the first and second rf stage. This would function as the set's volume control while at the same time preventing distortion from "front end overload" caused by local strong signals. Most likely, the colors are long since faded from your battery wires. I was still able to make out the original colors where the wires were inside and under the chassis.It is always a possibility that you may find a radio where the wires have been replaced. In this case, careful comparison of your set to the schematics will help you identify which wire should go where. About the batteries The A battery would have been 6 volts. Type 01 tubes draw .25 amps each, so the whole radio should draw about 1.25 amps, depending where the filament rheostat is adjusted. For loud local stations it was common practice to back off the filament voltage to prolong battery life. There is no meter of course, the control was turned down as much as possible while still delivering acceptable performance. There are two wires brought out for B batteries. There may have been more than one reason for this and if anyone should find any documentation on the set, let me know. The radio most likely used a 45 volt battery for the RF stage and a 90 volt for the audio, or it might have prevented degraded performance of the RF stage caused by fluctuations in battery voltage due the demands of the audio stage when the batteries were nearing the end of their life. My set gives satisfactory performance running both stages from a single 45 volt power supply if used with headphones. The 90 volts is required for driving a speaker. C batteries are used to create a negative bias on the grids of the audio tubes. The usually ranged between 3 and 22 volts depending upon the circuit design. The optimum voltage for the 01 tube is about 9 volts. The bias circuit draws very little current. A 9 Volt transistor battery would probably last its expected shelf life, even with everyday use. This is why the small batteries were often placed inside the cabinet. Applying too high of a C voltage will decrease the audio volume, by driving the tubes into the cut off region. Too low or no C voltage can do the same by allowing the tube to saturate, this also will cause the tubes to draw more current and reduce the life of the B battery. If you buy or build a battery eliminator, don't pay extra for one that supplies the C voltage, just use a 9 volt battery. Most vintage battery radios hold up well if they were stored in a reasonable environment. All three of the fixed capacitors in my set were within 10% of their rated values. The 2 meg bias resistor used on the detector was the only component that was out of spec, measuring in at 3.9 meg Ohms. All of the tubes tested OK.

The 2 meg ohm bias resistor looks like a fuse. That's not just a holder that it is in. Careful examination reveals that it is an early 25 pF mica capacitor, the value is stamped on one end. A similar capacitor without resistor clips is seen to the left

A case for using a type 12 output tube. As mentioned in the beginning of this article, the final audio stage was intended to drive the headphones or speaker directly. To drive a modern 8 ohm speaker you will need to use an output transformer salvaged from a more modern tube radio or amplifier. One taken from a 1940s / 1950s battery portable will offer the best match. Most of the horn type speakers, early direct drive paper speakers, and headphones had an impedance of 2000-4000 ohms. The early type 01 tube has an equivalent plate resistance of 10,000 ohms verses 4700 ohms for the type 12. This means that when used with most vintage speakers and certainly with a transformer and modern speaker, the Type 12 will produce more volume with lower distortion. All other characteristics of the two tube types are nearly identical, including filament voltage and current, and gain. Since using the type 12 requires no modification to the radio, it can always be changed back to type 01 for display in a judged show. If you have comments and and info that you would like to share, please e-mail me.