bmsgaffer 2,052 #1 Posted December 15, 2014 (edited) I am doing a little research on developing improved circuit boards for these tractors. I will be hitting the books but also lookin for some hands-on time. I know there were several models of circuit boards throughout the years, so I am wondering if anyone has a few not-completely-trashed circuit boards (throughout all ranges of years) that they would be wiling to donate to me to dissect (and I hope I can work with SOI on this) to further my research on a universal, or at least semi-universal replacement circuit board. I will be replacing all grain of wheat bulbs with LED's. Boards will be either potted once burned in (unrepairable, but weather proof) or conformal coated (repairable, but only weather resistant) Also will look into replacing the 3A charging diode with a real rectifier regulator. More to come, as it is very late now. Edited December 17, 2014 by bmsgaffer 1 Share this post Link to post Share on other sites
Save Old Iron 1,571 #2 Posted December 15, 2014 I just completed schematics in DipTrace last week for the 2nd gen 418 and the 1st gen 416 pcb's. I can post the schematics here and see if they are readable. The pcb design violates nearly every sensible rule known to sound EE principles. No voltage regulation, running TTL chips directly from 12 vdc, placing + and ground leads next to one another in a "molex meets manure" outdoor environment, no base current limiting on low hfe lamp driver transistors - the parade goes on....... I will look forward to your critique on the design. 4 Share this post Link to post Share on other sites
Lane Ranger 11,312 #3 Posted December 15, 2014 Best Wheel Horse news of the coming New Year is that you two are working on something together! Share this post Link to post Share on other sites
Save Old Iron 1,571 #4 Posted December 16, 2014 (edited) The 418a schematics DipTrace Schematic - 418a ind pcb test lights schematic.pdf 418A EDGE CONN PINOUT.pdf DipTrace Schematic - 418a ind PARK BRAKE SCHEMATIC.pdf DipTrace Schematic - 418a ind pcb CLUTCH Schematic.pdf DipTrace Schematic - 418a ind pcb PARKING BRAKE schematic.pdf DipTrace Schematic - 418a ind pcb PTO schematic.pdf DipTrace Schematic - 418a ind pcb SEAT SW schematic.pdf Edited December 16, 2014 by Save Old Iron 7 Share this post Link to post Share on other sites
Save Old Iron 1,571 #5 Posted December 16, 2014 some random thoughts ... why bother running the seat and parking brake signals thru logic ? why not just hardwire the lamps directly to the safety switch terminals and have done with it? the whole bill of material for the low oil light could be replaced with a single, self contained flashing LED wired directly to the oil pan switch. my schematics show a 1K ohm base current limit resistor in the schematics - this item is not present on the original pcb and causes some lamps to glow dimly even if the fault is not sensed by the indicator pcb - inserting the 1K resistors resolves the issue. notice the 470R resistor from the +12 volt supply to the VCC of the logic chip. This design actually (attempts) to use the voltage drop across the 470R resistor to supply voltage to the logic chip rated by the manufacturer at 4.7 to 5.1 volts DC. The actual voltage variance seen at the chip under normal circuit operation is 2.3 to 7.2 volts !!!! I removed a filter cap and inserted a 1 watt 5.1 volt zener across the power rails and recalculated the 470 shunt resistor to around 220 - 270R. This keeps the Vcc of the logic chip at 5.1 +/- .15 volts across the entire range of voltage supplied by the battery. The circuit works predictably across a range of 10 to 16 volts at the battery. 3 Share this post Link to post Share on other sites
km3h 543 #6 Posted December 16, 2014 Makes you wonder how these things last so long. You did a great job on those drawings by the way. Share this post Link to post Share on other sites
Molon_Labe 731 #7 Posted December 17, 2014 The 555 timer for the oil light flasher is a great idea! Share this post Link to post Share on other sites
cod 121 #8 Posted December 17, 2014 The 418a schematics Nick nailed it as the drawings are excellent!!! Now if I could only understand them. Electricity and I have danced together many times and it's a good thing I had dark curly hair ( in my younger days ) as no one could ever tell how many times I got jolted. Thanks Chuck!!! Perhaps based on what both you and Brandon are investigating could lead to a series of more robust/simplified boards or a single board that can be modified for multiple tractors. Cod Share this post Link to post Share on other sites
Save Old Iron 1,571 #9 Posted December 17, 2014 Nick nailed it as the drawings are excellent!!! Now if I could only understand them. Cod Steve, I will give a cursory explanation of how the circuits work to help those who have an interest in learning about electronics. Time wise, the next few weeks are going to be a little tight, so bear with me. 2 Share this post Link to post Share on other sites
bmsgaffer 2,052 #10 Posted December 17, 2014 Thanks SOI, that gives a great start. Does anyone have any toasted boards they can send me for measurements? I will take any and all versions. Share this post Link to post Share on other sites
meadowfield 2,713 #11 Posted February 18, 2015 Did you get any boards? would like to see a 1:1 scan and look at a high tech, simplified version using SMD Share this post Link to post Share on other sites
bmsgaffer 2,052 #12 Posted February 19, 2015 No one ever sent me one. I dont have any 300 or 400 series to use. It would be rather easy to implement, but since no one ever sent me any I couldn't do much. SOI had some dimensioned images that you should be able to get pretty close off of. Share this post Link to post Share on other sites
19richie66 17,602 #13 Posted March 9, 2015 Sent you a pm. I have a 418-a board you can have if this is still active Share this post Link to post Share on other sites
wrightorchid 261 #14 Posted March 12, 2015 What I thought was a 312 board is not the same as the one on my 312-8. I bought a 312 wiring harness complete, and it is different. The board has more wires going to it, and they are black with a colored stripe, whereas mine are a solid color. The connections are also different. It is in good condition, I just can't confirm which tractor it is for. Share this post Link to post Share on other sites
