| Grigsby 1870 ;Chassis (Rider : Majestic 10 P: 8) |
| £1.80 (~ $2.20 or €2.10) |
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| Country | USA |
|---|---|
| Manufacturer | Grigsby-Grunow (-Hinds) Co. (Majestic pre 1933); Chicago (IL) |
| Model | Majestic Chassis 180 - Grigsby-Grunow -Hinds Co. |
| Year: 1930 | Broadcast Receiver |
| Valves | 9: 27 27 27 27 27 50 50 81 81 |
| Technology | TRF without regeneration; 3 AF stages; Neutrodyne |
| Tuned Circuits | 4 AM circuits |
| Wave Bands | Broadcast only (MW). |
| Power Type | 90-130 Volts AC |
| Notes | Push-pull af output stage; using the 8P6 or 8P3 power unit; chassis for Majestic model 181.
This radio is a cascade of 3 individual TRF stages, each with its own feedback coil forming a Wheatstone bridge acting as a Hazeltine neutralization for the triode (described as the RFL circuit in contemporary sources). The feedback polarity is reversed with respect to the signal polarity through the Cag Miller-capacitance, in effect neutralising the triode tendency to oscillate. The antenna circuit has a separate tuning coil, to be readjusted with each tuned frequency. The tuning scale is graduated with 2 scales: One in frequency from 550 to 1500 kHz and the other as a linear scale from 0 to 100. LF coupling between stages is done by transformers - Push-pull output. The unit contains a separate 8P6 or 8P3 power supply unit with individual transformers for the filaments and the 425 Volt anode supply. A current regulator is included in the primary circuit of the power transformers to compensate for mains voltage changes between 90 and 130 Volt AC. |
| Source | MyFile: Majestic_Grigsby-60_70_72_70B_80_90_90B_100_100B_130A_Super Screen Grid_180_181_230A_Majestic_7BP3_7BP6_7P3_7P6_8P3_8P6_9P3-1930.Gernsback.Radio.pdf |
| Source | Book: Gernsback Vol: 1 Page: 193 |
| Source | MyFile: Majestic_Grigsby-20_21_22_23_30_31_50_52_60_61_62_70_71_72_70B_80_90_90B_100_100B_130A_160_163_Super Screen Grid_180_181_230A_Majestic_7BP3_7BP6_7P3_7P6_8P3_8P6_9P3-1933.Rider.Radio.pdf |
| Source | Book: Rider Vol: 1 Page: 8 |
| Source | Book: Rider Vol: 2 Page: 2 |