Random musings - usually on a technical (nerdy) subject - possibly related to amateur radio and also things discovered at aramuseum.org.com and also modulatedlight.org


Important:If you are at this web page you probably have a Polaris through a bad speedometer which method that friend can\"t placed it in 4 wheel drive and also your reverse override doesn\"t work. If this has happened come you, you probably ran it there is no a great battery - or through no battery in ~ all: read on to find out why you have to never execute that if friend can help it!There are at the very least two execution of speedometers used in the late 1990\"s and early 2000s - the one that, inside, watch like figure 4 through \"through-hole\" components and also a slightly newer version that mostly uses surface-mount components. While both versions seem to have actually the exact same fate when provided with a bad (or no) battery - and also the \"fix\" is most likely similar, I have not personally seen the more recent surface-mount version, but you can uncover information top top its repair near the bottom that this article as detailed by one of the readers.

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If girlfriend have efficiently repaired among these more recent versions and are ready to share the specifics, I\"d be happy to short article it here. If you have a \"dead\" speedometer the the more recent version and would likely me to take a cracked at resolving it (absolutely no guarantees around success!) climate feel free to call me via comments, below.Last year, a girlfriend of mine had actually the battery go poor on his 1999 Polaris Sportsman 500 4-wheeler. Aside from the inconvenience of having actually to pull-start it, it appeared to work OK.Sort of.Soon, it to be noticed the the speedometer had actually died and interestingly, a couple of other points quit working at the same time such together the ability to put it right into four-wheel drive. As soon as the battery was finally replaced the speedometer still did not work-related so a the dug about in the internet and found the this is fairly a common problem through that vintage that Polaris vehicles - and it seems to job-related out this way:The charging system\"s voltage regulator on this vehicles are relatively simple, yet they depend strongly on the existence of the battery to moderate the wildly pulsating DC coming out of the alternator/regulator device to preserve the average voltage in the range of 13.5-14.2 volts or so. If the battery goes totally bad or is removed, the charging mechanism goes haywire and the voltage have the right to (apparently) exceed 20 volts (and is probably higher) and one can risk burning the end the various indicator, marker and also headlights.Another fatality under this conditions seems to it is in the speedometer module itself!What (probably) happens:It\"s most likely not the high voltage that actually kills the speedometer: The voltage regulator circuit in the speedometer seems to be fairly robust, using high voltage (>=300 volt) transistors to stand up to the voltage spikes that room endemic to any kind of vehicle electrical system. What appears to kill these things is heat.Let me explain.The project of the voltage regulator circuit within the speedometer is to assure that the voltage feeding the circuit inside doesn\"t exceed around 15 volts or so and from there, the is regulation down also lower by various other circuitry for the computer system that gives the odometer readings and also (probably) the speedometer and also having miscellaneous to execute with the reverse limiter designed to stop you native accidentally steering backwards at a high rate and the lockout/controls for the all-wheel drive switch. Over there are also several little light bulbs inside the speedometer that administer backlighting for the display screen at night and also these, too, are safeguarded from high voltage through the 15 volt regulator.Under normal conditions the voltage top top the vehicle\"s electrical system is about 14 volts or so and also the regulator\"s task is come suppress spikes and brief excursions above that and also in this mode, the regulator chin isn\"t law much. If the voltage rises, however, it has to drop the excessive voltage and also and a herbal by-product the this is that it establishes heat.Apparently, fairly a bit of it! In testing the speedometer after the fix I applied 20 volts come it and the key regulator transistor soon acquired too hot to touch: If this had actually been a hot, summer day through the transistor crammed inside the waterproof speedometer casing through no complimentary air ventilation, it would have actually been much hotter.So, with the poor battery and also a subsequently malfunctioning charging system it is quickly likely the the speedometer\"s regulator observed an median of 20-30 volts ~ above its input. In ~ some allude the transistor overheated and also eventually failed internally, shorting chin out. Fortunately, the majority of the circuits in the speedometer seemed to make it through this since once the regulator itself had actually quit, all power feeding the rest of the circuit was lost completely, preventing further damage.While a brand-new speedometer is available as a replacement part, the will expense you numerous hundred dollars, new!Fortunately, that may be the you can solve it!The obligatory warnings, etc.Assume from the beginning that the speedometer is a complete write-off and also that friend would need to replace it, anyway. This way, if you deserve to fix it, you will be money ahead - but if you can\"t, you haven\"t shed anything more! Before friend start, review this entire posting so that you\"ll understand what you room in for! fix of the speedometer calls for some knowledge of electronics and also board-level electric components. Repair additionally requires great unsoldering and also soldering an abilities and tools - and a soldering \"gun\" doesn\"t count. If you don\"t have the appropriate tools and also experience in the replacement and also installation that individual, through-hole components, do not also attempt this! The speedometer is component of the electrical system of the vehicle and also as such, the is feasible that its break down - possibly because of a failed repair - can cause extr damage to various other components. No, ns won\"t repair your speedometer as with shipping, time, \"hassle factor\" and labor, I\"d have to charge a sizable percentage of the price of a new one. I indicate that you discover someone versed in electronics to assist you the end if you need to do so. I recognize ONLY about the speedometers top top Polaris Sportsman 500\"s because that the years 1999 and also 2000: If girlfriend ask me around speedometers for any other make, year or model, ns can\"t assist you! (They might be the very same - they might not - i don\"t know.)You do this fix at your very own risk! carry out not acquire mad in ~ me if you punch something up, collection fire to your four-wheeler or cause every one of your dog\"s hair to autumn out! Again, there appears to it is in a (newer?) version of the speedometer with much more surface-mount parts that can suffer the exact same fate. While I have not seen among these, personally, one of the readers has provided information around his successful repair: through his permission, I have actually posted this update close to the finish of this article.You have been warned!How to perform itRemove the speedometer: The an initial step is to remove the speedometer native the vehicle. It\"s a little bit of a pain, yet it\"s not terribly an overwhelming to do as the is virtually the exact same procedure as would certainly be adhered to for replacing the headlight.Inside the housing that covers the headlight you\"ll find two connectors the snap right into the speedometer, hosted in location with release tabs, as well as two nuts that hold the clip in place: Note just how these go with each other before taking them turn off - do a illustration and/or take it a picture before friend take whatever off if girlfriend aren\"t sure.Open the speedometer: Place the speedometer confront down ~ above a clean, un-cluttered job-related area ~ above a surface that you don\"t mind scratching: It\"s recommended that you placed a rag or old towel in between the confront of the speedometer and also the work-related surface.Now, an alert the soft, aluminum ring approximately its perimeter: This hold the clear, plastic cover to the human body of the speedometer through virtue that crimping between those 2 pieces a rubber gasket. Wearing leather gloves to avoid being stabbed during this step, use a medium-sized blade driver - preferably one the is somewhat worn out v rounded edges - and slide it in between the aluminum ring and the plastic human body of the speedometer ~ above the back side, prying the ring open up as you walk along, straightening it out. Through a little of exercise you can firmly slide the screwdriver follow me the perimeter and also straighten the end that soft, aluminum ring and you will certainly probably need to go around several time to do the job.
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Figure 6Used by permission that Mathias, this is a picture of the surface-mount version discovered in a 2000 Polaris Sportsman 335. That is thought to be (more or less) the very same circuitry as that shown in number 4, over - but using more surface-mount components.The thread of the related conversation - including a reference to the photo above - may be found in the comments below: Look because that those related to user \"Mathias999us\".Click ~ above the picture for a bigger version.
Figure 6, above, shows the surface-mount version that seems to endure the very same fate as soon as the unit is operation without a battery come moderate the voltage. The above drawing is annotated through some clarifications included below:TIP48 - This is the same power transistor (through-hole) as used in the older version. \"SMD marked 1Dt\" - This is the same function as the MPSA42 offered in the older version, other than surface mount. The instance marking of \"1Dt\" (assuming that the composing was deciphered correctly) is a little ambiguous, yet it describes an NPN transistor. The is thought to it is in a BC846 transistor - a general-purposes NPN maker that is rated for 65 volts.It must be provided that the MPSA42 is available in the very same SMD footprint together the over and is recognized as the \"PMBTA42\". This might be a much better choice 보다 the BC846 in terms of being able to manage voltage spikes, need to the Polaris it is in operated there is no a battery. \"Unidentified diode\" - There room two that these:The big one shows up to be just a traditional diode. If open/shorted, the surface-mount variation of the 1N4003 (through 1N4007) have to be fine.The small one is most likely a surface-mount variation of the Zener diode dubbed out above - specific a 15 volt unit.Capacitors: this aren\"t significant in figure 6, but they room the large, steel cans next to the TIP42.These are regularly damaged through the heat and voltage when the speedometer is operation without a battery.

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If one/both of this capacitors watch at every bulged or swollen, if the looks prefer their plastic labels have actually shrunk and split and/or if there is some sort of fluid coming out of castle - either from the seam ~ above the height or at the circuit plank - they have to be replaced!These are reportedly 470uF, 25 volt capacitors.Before remove them keep in mind which finish of the capacitors are marked with the minus authorize so that the new ones may be installed correctly.This page stolen indigenous aramuseum.org