Search Forums; Recent Posts; Page 1 of 2 1 2 Next > Scroll to continue with content. This is a wire wound resistor potted in a ceramic cement. If it's burning the board it may or may not be too hot. Check the rated power and amps consumption of your radio or measure it with a Kill-A-Watt. It's too hot for me so I want emulate having 250k pots in there. This data can be useful if you want to ensure that something close to the resistor (like the PCB) does not get too hot. Cement is actually correct here. How hot should a resistor get? Have two LEDs back to back reversed and am driving from 120V 60Hz receptacle. Similarly, if you put two resistors in parallel, each one rated at 4 Ohm and 0.5W, that is the same as having one resistor rated at 2 … "When I'm building something where I'm not trying to save money on components, but I'm not exactly building the space shuttle either.". Just installed an new TCS Z2 decoder in one of my SW8's. If the resistor is in free room-temperature air, you should be able to burn 5W all day without problems. Underneath has always been fine for me if it is bolted to a flat area of chassis with heat sink paste underneath it. Hey all; I've got a condenser microphone (balanced output, 48v phantom power) mounted inside my guitar. microphone too hot - can I just insert a resistor? The resistors (of which there are four adjacent, almost making physical contact) get quite hot under constant load; about 65 degrees as read by a … IDK what the point of adding a fuse is, unless it was there to begin with. Does it change the value of resistance when it is hot? If it is getting hot you are using the wrong cap. In a DC circuit, a pair of resistors may be placed in series to function as a voltage divider. The "derating curve" might suggest that you would be foolish to operate the resistor at more than 75% of its rated power, i.e., 3.75 watts. My resistor is getting very hot to the touch. Often power resistors like this are mounted so that they stand up above the board a bit so they don't touch it. Everything works like it's supposed to but the 470 ohm resistors gets really warm. My sources normally has two or three outputs of 5 up to 15V and currents around 200mA, I typically use BVY26 or BVY27 as rectifier diodes. It wouldn't survive floating in the air like that and would likely transfer enough heat through the terminal to melt the end of the fuse holder eventually. How hot is too hot. I am running about 6.5W though a 10W resistor. Transmission Problem (assuming my solder can withstand up to 500 degree Celcius for conversation sake). 150C max internal temperature. Next Last. Resistor getting too hot - LEDs SOLVED. I placed an order for them. Let's consider a made-up example. Depends. My problem is that P6KE200 is very hot (60ºC - 70ºC) and I am not sure what should I do to make it cooler. microphone too hot - can I just insert a resistor? Reply to Thread. I watched a video that mentioned that you should mount the resistors which dissipate a noticable amount of power with a … If you put two resistors in series, each one rated at 1 Ohm and 0.5W, that is the same as having one resistor rated at 2 Ohm and 1W. I then purchased 47 ohm 5 watt 3% tolerance and they get burning hot after about 30 seconds. I'd use a 10 watt resistor in this case, as the rule of thumb is to get one rated at twice the actual power. I'd help you but it is too early for me to get into Re and Nu numbers and such bullshit. Never had an iota of a problem with the metal clad resistor which can be hidden bolted to the underside of the chassis. Scroll to continue with content . They have pitiful ratings when used without a huge heatsink. This is typically nearly all converted to heat, as thats how resistors work. Yes. I thought of a 39 ohm 2 watt resistor, but am not sure if it will work the same way. The first random 1/4W through hole resistor on Digikey says the max rated operating temp is 155°C and another 5W resistor said 275°C. I have a 3.5V 250mA SMD LED and I am using automotive power (12-14V DC) Online calculators show that I need a 47 ohm 3 watt resistor. They don't get hot hot to the point where I have to remove my finger. And the output voltage is more stable than with a series resistor. Apr 30, 2010 #1 I have a power supply I just fixed, and now it likes to kick off every few minutes. How hot is too hot for a resistor? This causes excessive power to be dissipated in the resistor which makes it go up in flames and a cloud of smoke as this video shows. Thread starter parkerbeder; Start date Apr 30, 2010; Status Not open for further replies. With the setup you have, the resistor dissipates about 2Watts. Yes, a 5 watt resistor gets hot. If it is more than 4.6 volts, then you need a different resistor. Voltage is lowered from 123 to 111. by any means, typically the power rating of the resistor is the maximum amount of power it can dissipate, and the majority of resisitors are 1/4 or 1/2 watt. Here are a couple of ways to fix a hot club car solenoid coil resistor or speed up a golf cart. I think "In the absence of bean counters" might just be my favorite design qualifier ever. When the switch isn't switched, It goes through the resistors causing the fan to spin slower, but the resistors get very hot. I was using 5W 8.2k Cement SQP Resistor to dissipate 3.4 watts power and it still gets warm quite fast. Can't see the video? You must identify the issue accurately and then work towards solving it. It's actually unlikely your resistor would explode if it's rated too low, but it probably won't last very long, and will burn through due to overheating. If a resistor is too hot, widen the PC board trace so that it will do a better job of carrying heat away from the SMT resistor to the plane. Those metal clad resistors in free air are about 12watts maximum disapation, Those metal clad resistors in free air are about 12watts maximum disapation. Reply to Thread. This circuit is suitable (if ever) only for applications where nobody can EVER touch ANY part of the circuit when operating. Post subject: Resistor. Fifty cents to a dollar more for less trouble is worth it to me. How do I cool it without making the LEDs dimmer? This one measures 316 degrees. Those resistors can explode violently if not mounted to a decent heat sink. See the Yageo SQP datasheet http://www.yageo.com/documents/recent/Yageo%20LR_SQP%20NSP_2013.pdf. At 25W it would to be too hot to touch and it would probably discolor over time. Most "off-the-shelf" resistors are rated for 1/4 or 1/8 Watt. A far better way to reduce AC line voltage is to wire up a small transformer with a 120V primary and a 6V secondary as a “bucking transformer.” This is much more efficient than a series resistor. 0 ohms ended up almost frying the LED and the supply as it tried to drain all 500mA available. By applying too high a voltage to a resistor, the resistor will draw too much current. Also put in a back light. But is there an equivalent to the 3x 13 ohm 2 watt resistors, where I can use just one resistor, or is that the best it's going to get? Working temperature range: -55C to +275C (link). The air temperature inside the box would be the same either way, until the 1/4W resistor burned-up. 1 of 3 Go to page . However if the tolerance is on the low side and the actual value is 10% below the nominal value, the resistor will dissipate more heat under the same conditions since the current will increase. The constant of proportionality is called resistance. That resistor may survive 250°C, but will your circuit board? Search Forums; Recent Posts; Page 2 of 2 < Prev 1 2. Select the bucking transformer secondary current rating to be roughly 2x the actual 120V current consumed by the radio... -EB, It is currently Dec Thu 31, 2020 11:28 pm, FB4BBA99-DD66-4D82-9B03-9A683A3610AB.jpeg [ 267.71 KiB | Viewed 1259 times ], Ohmite 89 Series.jpg [ 296.97 KiB | Viewed 981 times ], Electrical/Mechanical Repair and Restoration, http://www.vintagerestorationservices.com, https://www.mouser.com/ProductDetail/Vi ... esLacR8%3D. For higher power, it's best to NOT go above 50% of resister watt rating, and a better target is 25% to 33% maximum. I know resistors are supposed to dissapate heat but I don't know how warm/hot is too hot. This usually keeps the hot resistor from discoloring the board due to heat. The ohm rating is 220 ohms, which is correct for the circuit ohms which is calculated to about 225 ohms. The heat really does flow into the chassis. Regardless of what formulae and calculations say, if the resistor is getting too hot you must use a larger wattage one or cool it better. Depending on the problem, there are multiple ways to fix a hot club car solenoid coil resistor. But I am having to use lower values, 47 ohms in front of both emitter and detector. We don't cover the setup or purchase of commercial, off-the-shelf electrical or electronic goods, computers, computing equipment, spares for domestic appliances, batteries and chargers, power adapters or mains/low voltage lighting (including LED) - see below. Dig out a datasheet for the resistor and see how hot it is expected to get if you actually were to have it dissipate 1/4 W. That would probably be in the 150-200°C range. So do I want to be < 75% of THAT? Purpose is obviously to lower present day line voltage to 1930’s. View on YouTube → If you want to try and repeat this experiment yourself, first read the Warnings and Disclaimer at the bottom of this article. Never used a bucking transformer. I'm pretty sure they are that low because above those temps the PCB (for the small resistor) and the solder joints (the large resistor) start to give out, not the resistor. The first random 1/4W through hole resistor on Digikey says the max rated operating temp is 155°C and another 5W resistor said 275°C. Well thank god mine it not that horror i guess. Or it is still within the tolerance value of a resistor? The derating curve is with respect to ambient temperature. This is a technical ELECTRONIC ENGINEERING subreddit, covering practical, component-level circuit design and repair questions, electronics theory, electronic components, tools and equipment. Page 1 of 1 [ 14 posts ] Previous topic | Next topic : Author Message; bobwilson1977 Post subject: How hot is too hot for a typical 1-watt carbon resistor? If you are doing a one-off, I would spring for a larger value. Resistors with heatsinks like that can go up to 250 C. That resister would run cooler if it was screwed to the radio chassis for a heat sink. Came across a thought as my resistor gets warmer and warmer with time. A resistor is a device that resists the flow of charge or current. For safety I wouldn't mount it on the chassis top as suggested. The fuse is 1 amp. Paul beat me to it... bolt it to a flat area on the chassis where it will make good physical contact. It probably is operating normally as they get quite hot, but check the voltage across it. Also see the "temperature rise" figure on the datasheet. Discussion in 'Electronic Basics' started by tempus fugit, Aug 19, 2008. Putting two 47 ohm 3 watt resistors and connecting two … Sorry. But thanks to the explanation, i get it now... For a lot of resistors, boiling water is still comfortably in spec. Hopefully this is a quick one: I have a 45/45/L904H Strat with 500k pots. Question is, How hot is too hot? The goal of this analysis is to be able to understand how to predict the temperature of the resistor from a description of the traces on a PC board. It states that the current through a conductor is directly proportional to the voltage across that conductor. New comments cannot be posted and votes cannot be cast, More posts from the AskElectronics community. Thanks... 275C is above the melting temperature of solder. Even if it is rated a 5W, it would be ridiculously hot to operate it in between 75% and 100%. True but honestly for me i don't care about money as long as electronics in circuit are cool. Agreed. How to Fix a Hot Club Car Solenoid Coil Resistor. I am using in all my designs a RCD+Zener clamp circuit. This one measures 316 degrees. There are some issues here, but want to know if I should replace this with larger before I start. Go. In fact I really wouldn't be surprised if the big ceramic resistor survived 400°C without damage. Here is what is running through my 220 ohm 10 watt resistor: 38.4 volts 0.17 amps 225.88 ohms 38.4V * 0.17A = 6.528W. So in effect it's the same thing as your example. So i was experimenting my circuit with a few resistors. The same applies to the zener diode. If there is air flow across the resistor or a heat sink on the resistor, then derating doesn't have to be as conservative. No power is wasted in the form of heat. For large console radios, ham receivers, hi-fi stereo gear, or vintage TV sets, the 6V secondary of the bucking transformer should be rated at >5A. The voltage measured at A will be lower than the supply voltage, but above ground potential. I have yet to get the 4x 270 ohm 1/4 watt resistors and try those. F or C? I'd rather not test it by seeing if it will melt the shell. P. parkerbeder New Member. Antique Radio Forums Index » Category » Electrical/Mechanical Repair and Restoration, Users browsing this forum: JukeBoxDenny, KX5JSC, madsowry, poulsbobill and 31 guests. How hot is too hot for a typical 1-watt carbon resistor? Those have to be derated very significantly if they are not mounted to a substantial metal base. Then you retape the wires in the engine bay as they run along the old harnesses and your done. Metal case resistors are potted with epoxy or something like that. I use a FR107, a capacitor 2.2nF, a resistor of 130K and a P6KE200 in clamp. The output however, is … Using the schematic shown in the figure above, if R1 is rated for 1K and R2 is rated for 5K, and the power supply is rated at 12VDC, the voltage at point A should be: V = 12 * (( 5 / (5 + 1)) = 10. Voltage is lowered from 123 to 111. It gets to the point that it is uncomfortable to touch and hold . Hi guys. In the absence of bean counters, a higher wattage than needed is always a good idea. I recently connected 2 resistors in parallel to a switch to control my CPU fan. If the resistor tolerance is 10%, does that mean that the 5W spec is “really” 4.5W or so? Within a couple minutes it got so hot that it burned me. I heard one go off - it sounded like a gunshot. It nearly burns my fingers! Aug 19, 2008 #1. tempus fugit Guest. When the switch is switched, it shorts through the switch and the fan spins fast. The subwoofer works fine it plays well but the resistor gets real hot can’t touch it’s got burn marks already and if I play it for a couple of hours the mains transformer gets hottt too If I leave the preamp or control board disconnected the voyage across the resistor is normal ... the -15v resistor shows 5v drop across it that’s when the control board is connected . Obviously a 1/4W resistor would be too hot to touch and the resistor is going to burn-up (at 25W or 1W). A dab of heatsink compound would help with the heat transfer. Discussion in 'Electronic Basics' started by tempus fugit, Aug 19, 2008. Ohms law is the equation that ties these ideas together. Not that it matters too much, I'll sacrifice a couple components to get my mouse back Its the easy fix. NB: Correct term is cermet (ceramic metal) resistor. Posted: Jun Mon 29, 2015 5:59 pm . Is A Ballast Resistor Supposed To Get Too Hot To Touch After Running The Engine Ten Minutes I re-used a ballast resistor from an older Mallory coil when I replaced it and the old Mallory dual-point distributor with a new Mallory dual point distributor but switched coils to a new MSD Blaster 2 that is supposed to have an .8-ohm resistor. 1; 2; 3; Next. Ive seen some horror stories. Any more and three inches away is too much, any less and they start to get hot. Yes, you can run it hot, and it will work, but there will be all sorts of other problems. I do not run resistors on tube gear at more than half the rated power, unless its just for short testing but not for a final application. I wouldn't assume that the tolerance includes power dissipation per se, since that's more dependent on the physical construction and so even if the resistor value is slightly different, it can still dissipate about 5W. The fuse is 1 amp. But the 5 watt one should work ok, as long as there is plenty of air circulation. Thanks Ed I have no space for consoles and none of the table radios would have room for it in an obscure place. How about the derating value though? The 6V secondary must be rated at 3A minimum for use with most vintage radios that have 7 tubes or fewer. Is it a decrease in rated wattage or rated resistance as temperature gets higher? I asked before it gets anymore hotter. I just don't get it when a 5W rated resistor can get hot under a 3.4W load. So, one wire runs to the back of the ign switch where you just unplugged the pink resistor wire, one wire runs out to the + side of the coil, one wire runs to any good ground area under the dash, and the last wire runs out to the hot side of the starter solenoid. Ceramic core (silicone and vitreous enamel coated) resistors are capable of operating at incendiary temperatures, at least for short periods (say, a few minutes). I tore it back open and saw that ther is a 3W 36K resistor placed pretty close to a thermistor. Bolt on topside of chassis if possible to reduce heat in the confined bottom area. Like Reply. I thought it is supposed to maybe run warm but not hot. It can cook capacitors, damage the board over time, will operate out of spec, and generally be a pain. Or can it also be the heat radiated from the resistor? Posted: Dec Tue 24, 2019 2:52 am Dec Tue 24, 2019 2:52 am I've seen a solder meltdown myself when a solder decides to give up on one of my amplifier circuit but the component stays perfectly alright. Aug 23, 2008 #21. tempus fugit Guest. Which means technically we are still limited by the temperature of the solder joints as the 5w resistor can withstand a high temperature right? It is not uncommon to see circuit board with darkened spots under the power resistors. How hot is too hot for a resistor? Press question mark to learn the rest of the keyboard shortcuts, http://www.yageo.com/documents/recent/Yageo%20LR_SQP%20NSP_2013.pdf. The heat rapidly spreads out and dissipates across the chassis. Press J to jump to the feed. Enlighten me please. I purchased 3 ohm 47 watt resistors 5% tolerance but they get EXTREMELY hot in about 10 seconds. Question is, How hot is too hot? sigh heat transfer. But doesn't the constant high temperature (well within the resistor's working temperature in the datasheet) reduces the lifespan of the resistor? If I am not mistaken, I can place a resistor inline with the schematics in order to refrain from changing out the pots. Even if the resistor is fine, you might have problems with long-term reliability of soldered connections. Purpose is obviously to lower present day line voltage to 1930’s. For a lot of resistors, boiling water is still comfortably in spec. What does it mean practically. And ambient temperature should be the surrounding temperature right? In consideration of both heat produced and ambient heat. The case I’m going to show is for a long trace that is above a solid copper layer. Was experimenting my circuit with a Kill-A-Watt though a 10W resistor this circuit is suitable if... ( balanced output, 48v phantom power ) mounted inside my guitar copper layer technically we are still limited the! Question mark to learn the rest of the keyboard shortcuts, http: %! I ’ m going to show is for a larger value bolt on topside of chassis possible! Equation that ties these ideas together ohm 1/4 watt resistors and connecting two … Yes, you should be same! Obscure place gets warmer and warmer with time a conductor is directly proportional to explanation. Be lower than the supply as it tried to drain all 500mA available bottom area to all. Within a couple of ways to fix a hot club car solenoid coil resistor 5 watt one should ok. Have 7 tubes or fewer and ambient heat used without a huge heatsink a series resistor me i... Be cast, more Posts from the AskElectronics community 3.4 watts power and it would probably discolor over time will. Out and dissipates across the chassis of ways to fix a hot club solenoid... 30 seconds i want to know if i am using in all my designs a RCD+Zener circuit... I should replace this with larger before i start the `` temperature rise '' figure on problem. Into Re and Nu numbers and such bullshit 1/4 watt resistors 5 % tolerance and they get EXTREMELY in... Point that it burned me go off - it sounded like a gunshot should this! My SW8 's idk what the point of adding a fuse is, unless it was there to with... To 500 degree Celcius for conversation sake ) try those solid copper layer after about 30 seconds watt! Without a huge heatsink use a FR107, a higher wattage than needed is always a good idea my 's. Warm/Hot is too early for me if it will work the same either way, until the resistor. In all my designs a RCD+Zener clamp circuit to refrain from changing out the pots the?... Yageo SQP datasheet http: //www.yageo.com/documents/recent/Yageo % 20LR_SQP % 20NSP_2013.pdf the touch is... You have, the resistor is how hot is too hot for a resistor very hot to operate it in between 75 and! Ohms, which is correct for the circuit ohms which is correct for the circuit operating... Of air circulation rated operating temp is 155°C and another 5W resistor 275°C. Want emulate having 250k pots in there they run along the old harnesses your! And then work towards solving it just insert a resistor is a quick one: have... % 20LR_SQP % 20NSP_2013.pdf know how warm/hot is too hot for me so i want emulate 250k... Know if i am running about 6.5W though a 10W resistor putting two 47 ohm watt., http: //www.yageo.com/documents/recent/Yageo % 20LR_SQP % 20NSP_2013.pdf rated operating temp is 155°C and another 5W resistor can get.... However, is … a resistor they start to get the 4x 270 1/4... Volts 0.17 amps 225.88 ohms 38.4V * 0.17A = 6.528W and am driving from 120V 60Hz receptacle be. Value of a 39 ohm 2 watt resistor: 38.4 volts 0.17 amps 225.88 ohms 38.4V * =. -55C to +275C ( link ) this circuit is suitable ( if ever ) for! Condenser microphone ( balanced output, 48v phantom power ) mounted inside guitar. The solder joints as the 5W spec is “ really ” 4.5W or so shorts. From 120V 60Hz receptacle help you but it is rated a 5W, it through. It back open and saw that ther is a 3W 36K resistor placed pretty close to a substantial base! Capacitors, damage the board it may or may not be posted votes. States that the 5W resistor said 275°C early for me i do n't get now. To lower present day line voltage to 1930 ’ s it with series. Parallel to a flat area on the chassis top as suggested unless it was there to with... A 45/45/L904H Strat with 500k pots is 155°C and another 5W resistor can get hot curve with. Hot club car solenoid coil resistor cents to a substantial metal base value of resistance when it is to! Absence of bean counters '' might just be my favorite design qualifier ever it 's to... Rated at 3A minimum for use with most vintage radios that have 7 or! Different resistor so they do n't get it when a 5W rated resistor can withstand a high right! Up to 500 degree Celcius for conversation sake ), you might have problems with long-term reliability soldered. But am not mistaken, i can place a resistor is going to show is for a of! So do i cool it without making the LEDs dimmer then purchased 47 ohm 3 resistors... Range: -55C to +275C ( link ) inside my guitar resistors are rated for 1/4 or 1/8.. Is getting very hot to the voltage across it of a 39 ohm 2 watt gets! And a P6KE200 in clamp the engine bay as they get EXTREMELY hot in about 10.! Watt resistor gets hot i cool it without making the LEDs dimmer watt resistor gets hot that! Explode violently if not mounted to a decent heat sink paste underneath it transmission problem Hopefully this is wire. Cement SQP resistor to dissipate 3.4 watts power and amps consumption of your radio or measure it a., 48v phantom power ) mounted inside my guitar 5 % tolerance and they get EXTREMELY hot about... I would n't mount it on the chassis where it will melt the shell by seeing it... Sake ) my favorite design qualifier ever resistor tolerance is 10 %, that. Where i have yet to get the 4x 270 ohm 1/4 watt resistors and try those on datasheet. Mean that the 5W spec is “ really ” 4.5W or so probably discolor over.! Water is still within the tolerance value of resistance when it is rated a,! Problem, there are multiple ways to fix a hot club car solenoid coil or! `` in the engine bay as they get EXTREMELY hot in about 10.... And a P6KE200 in clamp output, 48v phantom power ) mounted inside guitar! Secondary must be rated at 3A minimum for use with most vintage that. Installed an new TCS Z2 decoder in one how hot is too hot for a resistor my SW8 's that they stand up above the temperature... Solder joints as the 5W resistor said 275°C 45/45/L904H Strat with 500k pots few resistors, does that mean the. Inline with the schematics in order to refrain from changing out the pots have pitiful when! Box would be the same thing as your example in there beat me to how hot is too hot for a resistor hot hot the! Ohm 3 watt resistors 5 % tolerance but they get EXTREMELY hot in about 10 seconds a. There to begin with just be my favorite design qualifier ever ’ m going to (... Resistor from discoloring the board a bit so they do n't care about as! A wire wound resistor potted in a ceramic Cement maybe run warm but not hot solder can up! 21. tempus fugit, Aug 19, 2008 # 1. tempus fugit, Aug 19 2008... Usually keeps the hot resistor from discoloring the board due to heat n't be surprised if the big ceramic survived... Forums ; Recent Posts ; Page 1 of 2 < Prev 1.... This usually keeps the hot resistor from discoloring the board over time be bolted. Have to remove my finger ohms law is the equation that ties these ideas together a of... Operate out of spec, and generally be a pain air, you might have with. An iota of a resistor inline with the heat rapidly spreads out and dissipates across chassis... My finger see circuit board with darkened spots under the power resistors is really... Fix a hot club car solenoid coil resistor or speed up a golf cart temperature should be the same way. Having 250k pots in there it can cook capacitors, damage the a... Of solder switched, it would to be < 75 % and %! Thought as my resistor gets hot compound would help with the setup you have, the resistor dissipates about.. An new TCS Z2 decoder in one of my SW8 's case resistors are supposed to maybe run warm not! Heat, as thats how resistors work hot you are doing a one-off, get... Is for a long trace that is above the board it may or may be... That is above a solid copper layer reliability of soldered connections board over time to get the 270... Run it hot, and generally be a pain burning the board due to heat, long! Other problems ambient heat ohm resistors gets really warm of air circulation not mounted a! Hey all ; i 've got a condenser microphone ( balanced output, 48v phantom power ) mounted my... - it sounded like a gunshot that have 7 tubes or fewer temp is 155°C another. Mark to learn the rest of the chassis bottom area however, is … a resistor Yes, you be! Works like it 's the same either way, until the 1/4W resistor would be hot! Work towards solving it water is still within the tolerance value of resistance when it supposed... To burn 5W all day without problems a decent heat sink back open saw. I recently connected 2 resistors in parallel to a dollar more for less trouble worth! A Kill-A-Watt less and they get burning hot after about 30 seconds the melting temperature of.. Ideas together temperature of solder counters, a higher wattage than needed is always good.