Shamrock Radio Shamrock 28-29
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Marti Model 2R
Numerous requests have been received for circuit diagrams of Marti receivers. In Figure 8 you will find the schematic wiring diagram of the Marti Model 2R - 10. It has often been repeated by service men that many changes were made in these receivers and that no two of them are alike in every respect. The values and circuit shown in Figure 3 were obtained from receiver bearing the serial number 4400. Oscillation and low volume are the chief troubles encountered with this model. Excepting the terminals of the transformer, choke and volume control assembly there are few if any soldered connections, the leads being comprised of straps secured by | bolts and nuts. It is imperative that all nuts and bolts are tightened securely to avoid oscillation. Low volume is usually attributed to defective coupling resistors. The model 2R - in employs Kellogg type tubes in the r. f., detector, first and second audio stages.
Model 2R-10 Marti and the Shamrock diagrams reproduced by courtesy of RADIO MERCHANT, November 1933.
Marti Model T
The schematic diagram of the Marti Model T is shown on this page. This, of course, is an early model receiver, but the diagram has not been easily obtainable.
It is seen to consist of three stages of tuned tof, detector of the grid leak and con denser type, two stages of resistance coupled a - f and a single type 210 tube in the power stage. The power unit employs a type 81 half - wave rectifier and a double filter with the second section tuned to resonance in the vicinity of 60 cycles.
The volume control is seen to be in the antenna circuit. In the same circuit is a switch which permits changing from a regular antenna installation to the use of the light line as an antenna.
Shamrock Wiring Diagram
Two requests have been received for in formation regarding the connection of the volume control unit in the Shamrock receiver, The total resistance of the volume control assembly is approximately 7,800 ohms with a fixed tap at 4500 ohms to supply the detector plate voltage.