| Train Module Main Page | Circuitry | Assembly and Tuning | Parts List |
Assembly, Tuning the Module, and the Horn SectionAs a reference you may wish to print out the page containing the circuit diagrams or open up a new window.ASSEMBLY I used a small perforated board approx. 4”X2” and located the component as they appear on the schematic it is recommended that sockets be used for the IC’s, use a 8 pins socket for IC-1 , note that IC-1 has only 6 pins and R3 could be mounted on the remaining 2 pins, Variable resistors used were 3/8” square PC mount type, small rectifier bridges were used but individual rectifier diodes rated at 50v/.5a can be used with loss of usable surface.S1 and the horn button are mounted on top of the enclosure as well as connectors of your choice for input supply connections to Pos 4 to 7, the speaker would sound better if it were situated somewhere within the train area. Colour coded wire #20-22 is advised for your input connections for easy identification. DO NOT INSTALL THE IC'S UNTIL A COMPLETE VOLTAGE CHECK IS DONE TUNING THE MODULE Set speed control R1 to minimum and close S1 ,measure voltage between ground and S1 it should be 12VCD, measuring from ground to the junction of R3,ZD1 and R4, increase the speed control R1 to about 75% of its max and readjust until approx. 4.5V is just coming on. Return the speed control to minimum and repeat by increasing slowly and observe that the zener voltage increases at the same rate to its maximum value at 75% of the control setting. Turn S1 off and check that the supply voltage is now zero. Disconnect the ACV input and insert the IC’s with care that pin #1 is at the proper position, adjust R6 and R9 to mid-point and R13 to one third rotation, do not readjust R1 at this time. Apply AC power to the module and check for excessive current or hot IC’s, ensure that R1 is set to minimum and if everything has gone as predicted at this point you should hear the sound of the diesel engine at the speaker. Increase the speed control to its max. and adjust R6 for the max. RPM desired, readjust R1 if necessary, remember a little goes along way, now reduce the speed control to minimum and adjust idle speed with R9 for a feel of 1000 rpm then lock those settings. A this point you can adjust the gain control R13 to the desired level after you have situated the speaker where you will normally use it .If you have installed DIP switches in series with the diodes you have now a choice of selecting the diesel sound you prefer by turning the counter outputs on or off. THE HORN SECTION The Horn section as been designed with the least number and basic parts possible. A good simulation is obtained, naturally the larger the speaker used (up to a point) the better the sound. Ensure the speed control is set to minimum and press the Horn button, I expect you should hear something which may not sound like a diesel horn yet, since there is no volume control in the horn section it should be fairly loud, at least louder than the diesel sound which is the way it should be. Now adjust R18 to the point where the two frequencies are about to interfere with one another then very slowly readjust R18 where the sound is closest to a true diesel horn, at this point set the diesel speed control to its 75% limit point and activate the horn, there might be a slight warbling effect, if so , readjust R18 slowly to it most pleasing effect, readjust R13 if needed before closing. This was a fun project and I hope you enjoy its many sound effects
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