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troubleshooting method for micro-controller board ?
Jamie wrote: I have an idea for you. get your self a low voltage auto tail light lamp. use it in place of the fuse that blows. start disconnecting things until the lamp glows dim or not at all. this will allow you to keep the circuit on, you can then track down some heat traces which won't be much.. actually, you'll be able to do a volt tracking using that method.. You might have some logic issues that is causing current to exist only when the circuit is fired up. Good Lord. You made a suggestion that's slightly sensible ! Lightbulbs do make practical current limiters when selected appropriately. In this case an auto 12V lightbulb will be no good however, the volts involved won't even barely make it warm. I'd initially suggest a 1.5V or 3V type. Then it may serve some purpose. Graham |
troubleshooting method for micro-controller board ?
Eeyore wrote:
Jamie wrote: I have an idea for you. get your self a low voltage auto tail light lamp. use it in place of the fuse that blows. start disconnecting things until the lamp glows dim or not at all. this will allow you to keep the circuit on, you can then track down some heat traces which won't be much.. actually, you'll be able to do a volt tracking using that method.. You might have some logic issues that is causing current to exist only when the circuit is fired up. Good Lord. You made a suggestion that's slightly sensible ! Lightbulbs do make practical current limiters when selected appropriately. In this case an auto 12V lightbulb will be no good however, the volts involved won't even barely make it warm. I'd initially suggest a 1.5V or 3V type. Then it may serve some purpose. Graham Jesus.. If only I could really direct that in proper context to you with out offending some one else here. If you really knew how to debug things (something I learned from those that really knew what they were doing at age 13), the incandescent lamp has always been the choice of current regulators in debugging and in practical use of circuits. And in his case, 3 volt lamp is to low of voltage. come on , you can do better than that!.. You must have one that is at least rated to the voltage set you are connecting it into.. In this case, 5 VOLTS.. and that means a common 12 is fine for current testing. 6 volt at the smallest. Please come back later when you have something that is worth absorbing. I may even thank you, although I doubt it. As you pointed out indirectly or directly before, I can be just as rood an obnoxious as you can! -- "I'm never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5 |
troubleshooting method for micro-controller board ?
Jamie wrote: Eeyore wrote: Jamie wrote I have an idea for you. get your self a low voltage auto tail light lamp. use it in place of the fuse that blows. start disconnecting things until the lamp glows dim or not at all. this will allow you to keep the circuit on, you can then track down some heat traces which won't be much.. actually, you'll be able to do a volt tracking using that method.. You might have some logic issues that is causing current to exist only when the circuit is fired up. Good Lord. You made a suggestion that's slightly sensible ! Lightbulbs do make practical current limiters when selected appropriately. In this case an auto 12V lightbulb will be no good however, the volts involved won't even barely make it warm. I'd initially suggest a 1.5V or 3V type. Then it may serve some purpose. Graham Jesus.. If only I could really direct that in proper context to you with out offending some one else here. If you really knew how to debug things (something I learned from those that really knew what they were doing at age 13), the incandescent lamp has always been the choice of current regulators in debugging and in practical use of circuits. And in his case, 3 volt lamp is to low of voltage. come on , you can do better than that!.. You must have one that is at least rated to the voltage set you are connecting it into.. In this case, 5 VOLTS.. and that means a common 12 is fine for current testing. 6 volt at the smallest. Please come back later when you have something that is worth absorbing. I may even thank you, although I doubt it. As you pointed out indirectly or directly before, I can be just as rood an obnoxious as you can! YOU'RE A ****ING IDIOT. DON'T UPSET THE OP'S ATTEMPS TO FIX HIS PROBLEM WITH YOUR USELESS SHIITY IDEAS. Graham |
troubleshooting method for micro-controller board ?
"robb" wrote in message ... "Eeyore" wrote in message ... wrote: "robb" wrote: no shorts on any of the power regulator chips 5v L387 or the L298s and still get 76 ohm continuity between 5v an 0v ref. Ummm, what's wrong with that? I = E/R: 66mA. This (static) current isn't blowing the fuse. Yes. I thought it was a SHORT ! Not 76 ohms ! Looks like there may be hope yet. Graham apologies graham and anyone else who thpught i knew what i was saying :{ well i did say i was an amateur, i guess everyone forgot to ask me if i plugged it in :} ok, well i thought any thing less than couple of 100K Ohms was bad news ( rather a short ) i said short because my meter (fluke 177) has continuity setting that measures anything less than 250 Ohms as having continuity (beep) and i thought this was a bad thing between high/low that is 5v and 0v rails so does this new light change my tactics any ? maybe all are to upset with my mis-use of "short" ? still in need of help, robb It depends on the type of IC's, but a couple hundred ohms is not uncommon for a fully functional circuit. "Shorted" implies near zero ohms, maybe 1 or 2 ohms of resistance in the traces and connectors leading into the thing. |
troubleshooting method for micro-controller board ?
Eeyore wrote:
Jamie wrote: Eeyore wrote: Jamie wrote I have an idea for you. get your self a low voltage auto tail light lamp. use it in place of the fuse that blows. start disconnecting things until the lamp glows dim or not at all. this will allow you to keep the circuit on, you can then track down some heat traces which won't be much.. actually, you'll be able to do a volt tracking using that method.. You might have some logic issues that is causing current to exist only when the circuit is fired up. Good Lord. You made a suggestion that's slightly sensible ! Lightbulbs do make practical current limiters when selected appropriately. In this case an auto 12V lightbulb will be no good however, the volts involved won't even barely make it warm. I'd initially suggest a 1.5V or 3V type. Then it may serve some purpose. Graham Jesus.. If only I could really direct that in proper context to you with out offending some one else here. If you really knew how to debug things (something I learned from those that really knew what they were doing at age 13), the incandescent lamp has always been the choice of current regulators in debugging and in practical use of circuits. And in his case, 3 volt lamp is to low of voltage. come on , you can do better than that!.. You must have one that is at least rated to the voltage set you are connecting it into.. In this case, 5 VOLTS.. and that means a common 12 is fine for current testing. 6 volt at the smallest. Please come back later when you have something that is worth absorbing. I may even thank you, although I doubt it. As you pointed out indirectly or directly before, I can be just as rood an obnoxious as you can! YOU'RE A ****ING IDIOT. DON'T UPSET THE OP'S ATTEMPS TO FIX HIS PROBLEM WITH YOUR USELESS SHIITY IDEAS. Graham Useless? I bet it's adding to your education, arm chair bull **** artist. It's you that seems to have problems. As you once posted and I replied. Eeyore = "Think" Jamie = "Practice what you post" If you don't live by your own rules, then what gives you the right to push such rules onto others? You must be a real party animal. I bet you sit back there by your self and do nothing but find fault in every one and everything. And i'm sure you let any one that will listen to you know about it. Does that sound about right? -- "I'm never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5 |
troubleshooting method for micro-controller board ?
On Nov 7, 3:47 pm, "robb" wrote:
wrote in message ps.com... On 7 Nov, 20:40, "robb" wrote: ... As someone else pointed out, 73 ohms at 5V means a static draw of 5/73 = (about) 68 mA, which for a digital circuit sounds reasonable imho. It is definitely not a short. What's the fuse rating on the 5V rail? the fuse was a "T 630 mA 250v" so slow blow bussman type fuse originally the 5v fuse blew i checked transformer out put then replaced and powered and then all three fuses blew the 5v 12v 30v maybe i need to take a closer look at the power regulators again Yeah - I was thinking that the fuses were on the DC rails, but reading your original post again you state that they are between the transformer and rectifiers. But you also said that there were two rectifiers (on 8 [or 12]V, and on 32 [or 30]V). What about the 5V rectifier? And did you check those bridges for shorted diodes? That continuity wouldn't necessarily show up downstream (especially with the fuses blown). TM |
troubleshooting method for micro-controller board ? (trying bulb trick)
"Jamie" t wrote in message ... robb wrote: I have an idea for you. get your self a low voltage auto tail light lamp. use it in place of the fuse that blows. start disconnecting things until the lamp glows dim or not at all. this will allow you to keep the circuit on, you can then track down some heat traces which won't be much.. actually, you'll be able to do a volt tracking using that method.. You might have some logic issues that is causing current to exist only when the circuit is fired up. ok Jamie i tried this idea with a few compromises and tangents I only had 110 v bulbs and lattern light bulbs (~ 6V) so i used my lattern lightbulb and the lattern battery (showing 5.2 Volts) as my power source no components or tracks were wam enough to discern a change after several applications of power with increasing time .... so i inserted the milliAmp meter (the DMM) and that showed ~160 mA with the 6V bulb in series and note the bulb was not shinning as bright as it could. so i removed the bulb and i get ~428 mA without the bulb and the only thing that gets noticeably warm (*but* no more than prior to the ZAP) is the 8051 procesor this same result occurs no matter where along the 5V rail i apply/inject the 5V .... so i am not sure what this means, maybe good news ?? thanks for any help, robb |
troubleshooting method for micro-controller board ?
"Eeyore" wrote in message ... wrote: "robb" wrote: no shorts on any of the power regulator chips 5v L387 or the L298s and still get 76 ohm continuity between 5v an 0v ref. Ummm, what's wrong with that? I = E/R: 66mA. This (static) current isn't blowing the fuse. Yes. I thought it was a SHORT ! Not 76 ohms ! Looks like there may be hope yet. well i tried the light bulb load ( using a 6v lantern flashlight bulb) and using a lattern battery as power source. i could not find anything warmed and the DMM milliAmp meter shows ~ 138 mA i get ~438 mA when i disconnect the light bulb ??? and the 8051 IC is the only thing that is warmed but no nore than it warmed before the 32v rail mixing with the 5v i do not know what this means , hopefully something good robb |
troubleshooting method for micro-controller board ?
"robb" wrote in message ... "Eeyore" wrote in message ... wrote: "robb" wrote: no shorts on any of the power regulator chips 5v L387 or the L298s and still get 76 ohm continuity between 5v an 0v ref. Ummm, what's wrong with that? I = E/R: 66mA. This (static) current isn't blowing the fuse. Yes. I thought it was a SHORT ! Not 76 ohms ! Looks like there may be hope yet. well i tried the light bulb load ( using a 6v lantern flashlight bulb) and using a lattern battery as power source. i could not find anything warmed and the DMM milliAmp meter shows ~ 138 mA i get ~438 mA when i disconnect the light bulb ??? and the 8051 IC is the only thing that is warmed but no nore than it warmed before the 32v rail mixing with the 5v i do not know what this means , hopefully something good robb The 8051 was getting warm? I didn't think those produced enough heat to feel? |
troubleshooting method for micro-controller board ? (trying bulb trick)
"robb" wrote in message ... "Jamie" t wrote in message ... robb wrote: I have an idea for you. get your self a low voltage auto tail light lamp. use it in place of the fuse that blows. start disconnecting things until the lamp glows dim or not at all. this will allow you to keep the circuit on, you can then track down some heat traces which won't be much.. actually, you'll be able to do a volt tracking using that method.. You might have some logic issues that is causing current to exist only when the circuit is fired up. ok Jamie i tried this idea with a few compromises and tangents I only had 110 v bulbs and lattern light bulbs (~ 6V) so i used my lattern lightbulb and the lattern battery (showing 5.2 Volts) as my power source no components or tracks were wam enough to discern a change after several applications of power with increasing time .... so i inserted the milliAmp meter (the DMM) and that showed ~160 mA with the 6V bulb in series and note the bulb was not shinning as bright as it could. so i removed the bulb and i get ~428 mA without the bulb and the only thing that gets noticeably warm (*but* no more than prior to the ZAP) is the 8051 procesor this same result occurs no matter where along the 5V rail i apply/inject the 5V .... so i am not sure what this means, maybe good news ?? thanks for any help, robb Well, I would have to say that it certainly indicates that you are not chasing down any kind of permanent 'short' on your 5v rail. So now that you know where the 5v rail comes off the end of the LM317 (was it ?), can you disconnect it from that point, leave the fuses out of the 12 and 30v feeds, and hook the unit back to line power, with a 5v fuse in place ? Measure the IN, SET and OUT pins of the '317 to see what you get, and if you get a correct 5v on the OUT pin, then hook it back to the rail that you disconnected, which is then just the same as hooking your battery to it. I would expect all to be well, and you to get exactly the same result as with your battery. Once you've established that the 5v is ok, take it's fuse back out, figure where the 12v rail is regulated, and disconnect it in the same way. With a fuse in the 12v feed, apply line power, and measure the regulator pins. This may be another '317 set for 12v, or might be a 7812. If you have 12v correctly on the output of the regulator, then connect it back up and see what happens. If it stays ok, then put the fuse back in the 5v, and measure both rails. Repeat it again for the 30v rail, which probably isn't regulated. You will have to locate it's smoothing cap, find the piece of print that carries the 30v away from this point, and into the board's circuitry (clue : I wouldn't expect this rail to go anywhere other than to the driver chips that you mentioned previously), and either find a link on it that can be removed, or put a scalpel through it. Once it has been thus disconnected, apply power with the 5 and 12v fuses removed, and measure the 30v at its smoothing cap. If it's there ok, refit the 12v fuse, and check both rails again. If ok, fit 5v fuse and check all three rails. Now assuming that you really do have a problem, at some point this test procedure will go off the rails, and that's the point that we need to know to be able to offer any *proper* fault-finding advice. How far had you got when everything was proceeding to plan? What happened then ... ? Finding faults on electronic equipment is something of an 'art', much like any other trade or skill, but it is based on firm principles, and these *must* follow a logical sequence (no pun intended - well, maybe a bit ;-} ) If you take time to stop and think about what the problem *is*, not what you *think* it is, then a logical test sequence will usually suggest itself to you. If you then follow that sequence religiously, and whilst you are still learning, write down the results, it should guide you slowly and surely to an end result, as your tests suggest dead ends and new branches. With experience, that part of the procedure goes on in your head. So just take a minute to STOP and then THINK. Try the sequence that I suggested, and then STOP again, and EVALUATE what you have found. Good luck with it d;~} Arfa |
troubleshooting method for micro-controller board ?
robb wrote: well i tried the light bulb load ( using a 6v lantern flashlight bulb) and using a lattern battery as power source. Lucky that 6V is *just* acceptable. i could not find anything warmed and the DMM milliAmp meter shows ~ 138 mA i get ~438 mA when i disconnect the light bulb ??? You mean when you apply the battery directly to the 5V line ? and the 8051 IC is the only thing that is warmed but no nore than it warmed before the 32v rail mixing with the 5v i do not know what this means , hopefully something good robb It means that the power consumption looks to be in the normal range. Replace the 5V regulator (with a known good working one or test the one you have but best a new one) and power the board up on AC (but with the power peripherals unpowered - remove the fuse suppling power to those parts). Graham |
troubleshooting method for micro-controller board ?
James Sweet wrote: The 8051 was getting warm? I didn't think those produced enough heat to feel? I seem to recall that the NMOS versions (which he has) draw a little over 100mA. Graham |
troubleshooting method for micro-controller board ?
"Eeyore" wrote in message ... James Sweet wrote: The 8051 was getting warm? I didn't think those produced enough heat to feel? I seem to recall that the NMOS versions (which he has) draw a little over 100mA. Graham the datasheet says 125 mA dissipates 1W |
troubleshooting method for micro-controller board ?
robb wrote: "Eeyore" wrote James Sweet wrote: The 8051 was getting warm? I didn't think those produced enough heat to feel? I seem to recall that the NMOS versions (which he has) draw a little over 100mA. the datasheet says 125 mA dissipates 1W 125 mA sounds about right. That's 625mW not 1W though. The datasheet value for dissipation is almost certainly the maximum theoretical allowed value. Graham |
troubleshooting method for micro-controller board ? (trying bulb trick)
On Nov 8, 4:49 am, "Arfa Daily" wrote:
Well, I would have to say that it certainly indicates that you are not chasing down any kind of permanent 'short' on your 5v rail. So now that you know where the 5v rail comes off the end of the LM317 (was it ?), can you disconnect it from that point, leave the fuses out of the 12 and 30v feeds, and hook the unit back to line power, with a 5v fuse in place ? Measure the IN, SET and OUT pins of the '317 to see what you get, and if you get a correct 5v on the OUT pin[...] If the voltage isn't correct (e.g. 4.8-5.2V) at that point (but the fuse isn't blown) tack a 470 ohm resistor from the OUT pin to GND. The LM317 has a load regulation spec of 10 mA, and a minimum operating current of ~1mA (for low Vi-Vo); the adjust resistors may not be small enough to draw this much. And don't isolate the regulator by lifting the OUT pin, or you'll lose the adjust resistors. TM |
troubleshooting method for micro-controller board ?
"Eeyore" wrote in message ... robb wrote: well i tried the light bulb load ( using a 6v lantern flashlight bulb) and using a lattern battery as power source. Lucky that 6V is *just* acceptable. :) hi Graham, now i have learned a wee bit I pre-checked battery it was slightly drained and only showing 5.2 volts but still lighting the bulb ok so i thought that was close enough otherwise i would have found something as close to 5V as i could or even put a 5V regulator on a bread board i could not find anything warmed and the DMM milliAmp meter shows ~ 138 mA i get ~438 mA when i disconnect the light bulb ??? You mean when you apply the battery directly to the 5V line ? yes, that is more precise statement , i connected battery directly to 5V line to be clear about what i did do First Test - i connected the negative battery terminal of battery to the PCB 0v rail - i connected the positive battery terminal to bulb lead (bulb in series) - i connected DMM mA meter (in series) connect red lead to the free bulb connection - i connected the other free DMM lead of the DMM to the 5V rail of PCB that completed the circuit ||====================(138 mA)================.|| ||=(5v)PCB(0v)==(-)Battery(+)==()Bulb()==(+)DMM mA(-)=|| No heating noticed Second Test i removed the bulb from the circuit (essentially bypas te bulb and that gave a ~438 mA reading on the DMM mA meter noticed that the IC-CPU 8051 was a little warm and no other components or traces seemed to be seemed to be warming and the 8051 IC is the only thing that is warmed but no nore than it warmed before the 32v rail mixing with the 5v i do not know what this means , hopefully something good robb It means that the power consumption looks to be in the normal range. Replace the 5V regulator (with a known good working one or test the one you have but best a new one) and power the board up on AC (but with the power peripherals unpowered - remove the fuse suppling power to those parts). that is what i will do next , as it seems the 30 volt or 16 v out of rectifiers is what feeds the 5v regulator so i will need to do something about that thanks again for all your time and help, robb |
troubleshooting method for micro-controller board ? (trying bulbtrick)
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troubleshooting method for micro-controller board ? (trying bulb trick)
"Arfa Daily" wrote in message ... "robb" wrote in message ... "Jamie" t wrote in message ... robb wrote: I have an idea for you. get your self a low voltage auto tail light lamp. use it in place of the fuse that blows. start disconnecting things until the lamp glows dim or not at all. this will allow you to keep the circuit on, you can then track down some heat traces which won't be much.. actually, you'll be able to do a volt tracking using that method.. You might have some logic issues that is causing current to exist only when the circuit is fired up. ok Jamie i tried this idea with a few compromises and tangents I only had 110 v bulbs and lattern light bulbs (~ 6V) so i used my lattern lightbulb and the lattern battery (showing 5.2 Volts) as my power source no components or tracks were wam enough to discern a change after several applications of power with increasing time ..... so i inserted the milliAmp meter (the DMM) and that showed ~160 mA with the 6V bulb in series and note the bulb was not shinning as bright as it could. so i removed the bulb and i get ~428 mA without the bulb and the only thing that gets noticeably warm (*but* no more than prior to the ZAP) is the 8051 procesor this same result occurs no matter where along the 5V rail i apply/inject the 5V .... so i am not sure what this means, maybe good news ?? thanks for any help, robb Well, I would have to say that it certainly indicates that you are not chasing down any kind of permanent 'short' on your 5v rail. So now that you know where the 5v rail comes off the end of the LM317 (was it ?), can you disconnect it from that point, leave the fuses out of the 12 and 30v feeds, and hook the unit back to line power, with a 5v fuse in place ? Measure the IN, SET and OUT pins of the '317 to see what you get, and if you get a correct 5v on the OUT pin, then hook it back to the rail that you disconnected, which is then just the same as hooking your battery to it. I would expect all to be well, and you to get exactly the same result as with your battery. Once you've established that the 5v is ok, take it's fuse back out, figure where the 12v rail is regulated, and disconnect it in the same way. With a fuse in the 12v feed, apply line power, and measure the regulator pins. This may be another '317 set for 12v, or might be a 7812. If you have 12v correctly on the output of the regulator, then connect it back up and see what happens. If it stays ok, then put the fuse back in the 5v, and measure both rails. Repeat it again for the 30v rail, which probably isn't regulated. You will have to locate it's smoothing cap, find the piece of print that carries the 30v away from this point, and into the board's circuitry (clue : I wouldn't expect this rail to go anywhere other than to the driver chips that you mentioned previously), and either find a link on it that can be removed, or put a scalpel through it. Once it has been thus disconnected, apply power with the 5 and 12v fuses removed, and measure the 30v at its smoothing cap. If it's there ok, refit the 12v fuse, and check both rails again. If ok, fit 5v fuse and check all three rails. Now assuming that you really do have a problem, at some point this test procedure will go off the rails, and that's the point that we need to know to be able to offer any *proper* fault-finding advice. How far had you got when everything was proceeding to plan? What happened then ... ? Finding faults on electronic equipment is something of an 'art', much like any other trade or skill, but it is based on firm principles, and these *must* follow a logical sequence (no pun intended - well, maybe a bit ;-} ) If you take time to stop and think about what the problem *is*, not what you *think* it is, then a logical test sequence will usually suggest itself to you. If you then follow that sequence religiously, and whilst you are still learning, write down the results, it should guide you slowly and surely to an end result, as your tests suggest dead ends and new branches. With experience, that part of the procedure goes on in your head. So just take a minute to STOP and then THINK. Try the sequence that I suggested, and then STOP again, and EVALUATE what you have found. Good luck with it d;~} Arfa Wow Arfa thanks for all the great advice and feedback. it will take me several reply posts to address all your information the 5v regulator used is the L387 as it turns out it is powered by a feed from the 30 or 16 volt line which is my latest attempt to track. so i need to fnd if there is away to disconnect the 30v and 16 v feeds to other parts of the board to try your tests. still need to create a print out of the board as all this tracking is driving me bannanas thanks again for your ideas and help i will try and incorporate what i can nad see what results i can achieve , thanks, robb |
troubleshooting method for micro-controller board ?
"robb" wrote in message ... i have a micro-controller board with 3 big 40DIP ICs, 10 or so 16 DIP support ICs. with 32v/8v/5v transformer supply that connects to two bridge rectifiers {32v, 8v}a fuse links sit between transformer and rectifiers, no schematic. i believe the 32v shorted with 5V line and it blew one fuse link. the fuse link was replaced with same and when powered all three fuses blown. So....where does one start to diagnose such a *big* problem ? . Only thing working is transformer outputs and it seems like i get continuity hits everywhere i check the board was built about 1985 (no SMT) it is about 14" x 5" has 3 x 40 DIP ICs and 10 or so 16 DIP support ICs, handful of transistors many resistors,diodes etc, ideas and help would be greatly appreciated :) robb Its phutted! |
troubleshooting method for micro-controller board ? (trying bulb trick)
wrote in message ps.com... On Nov 8, 4:49 am, "Arfa Daily" wrote: Well, I would have to say that it certainly indicates that you are not chasing down any kind of permanent 'short' on your 5v rail. So now that you know where the 5v rail comes off the end of the LM317 (was it ?), can you disconnect it from that point, leave the fuses out of the 12 and 30v feeds, and hook the unit back to line power, with a 5v fuse in place ? Measure the IN, SET and OUT pins of the '317 to see what you get, and if you get a correct 5v on the OUT pin[...] If the voltage isn't correct (e.g. 4.8-5.2V) at that point (but the fuse isn't blown) tack a 470 ohm resistor from the OUT pin to GND. The LM317 has a load regulation spec of 10 mA, and a minimum operating current of ~1mA (for low Vi-Vo); the adjust resistors may not be small enough to draw this much. And don't isolate the regulator by lifting the OUT pin, or you'll lose the adjust resistors. TM Yes, good advice. Looking again, it seems it is an L387 regulator. I'll have to look that one up. It's so hard to cover all bases with someone who's at the 'practice' level. Things like making sure that the V-set resistors are still connected, is second nature when you do this sort of stuff all the time ... Arfa |
troubleshooting method for micro-controller board ? (trying bulb trick)
On Nov 8, 11:24 am, Eeyore
wrote: wrote: On Nov 8, 4:49 am, "Arfa Daily" wrote: Well, I would have to say that it certainly indicates that you are not chasing down any kind of permanent 'short' on your 5v rail. So now that you know where the 5v rail comes off the end of the LM317 (was it ?), can you disconnect it from that point, leave the fuses out of the 12 and 30v feeds, and hook the unit back to line power, with a 5v fuse in place ? Measure the IN, SET and OUT pins of the '317 to see what you get, and if you get a correct 5v on the OUT pin[...] If the voltage isn't correct (e.g. 4.8-5.2V) at that point (but the fuse isn't blown) tack a 470 ohm resistor from the OUT pin to GND. The LM317 has a load regulation spec of 10 mA, and a minimum operating current of ~1mA (for low Vi-Vo); the adjust resistors may not be small enough to draw this much. And don't isolate the regulator by lifting the OUT pin, or you'll lose the adjust resistors. It's not an LM317 though, it's some funny STM part, an L387. Oh. 5mA then, at least if it's the same as the L387A: http://www.st.com/stonline/products/...1337/l387a.pdf It's a fixed 5V regulator, so no Vset resistors. TM |
troubleshooting method for micro-controller board ? (trying bulb trick)
wrote in message ps.com... On Nov 8, 4:49 am, "Arfa Daily" wrote: If the voltage isn't correct (e.g. 4.8-5.2V) at that point (but the fuse isn't blown) tack a 470 ohm resistor from the OUT pin to GND. The LM317 has a load regulation spec of 10 mA, and a minimum operating current of ~1mA (for low Vi-Vo); the adjust resistors may not be small enough to draw this much. And don't isolate the regulator by lifting the OUT pin, or you'll lose the adjust resistors. umm.. i think you lost me,.... yes yes this place is familiar it is "lost land" as in i am lost i hope there is another way to do this as it sounds like i can cause more problems trying to find the problems ? if there is no other ways then i will just have to learn but the experience level of this diagnostic is really stretching my noodle(s) thanks for the help i am sure it is very useful advice and i just need to understand it. robb |
troubleshooting method for micro-controller board ? (trying bulb trick)
"Arfa Daily" wrote in message ... Yes, good advice. Looking again, it seems it is an L387 regulator. I'll have to look that one up. It's so hard to cover all bases with someone who's at the 'practice' level. Things like making sure that the V-set resistors are still connected, is second nature when you do this sort of stuff all the time ... Arfa well i am glad to have this advanced second nature diagnostics helping but it is Zero nature foreign to me though i am trying to understand it before i blow more components. i am very happy to have the help from everyone that know so much as i surely would have fried it worst if possible than it already is. i suppose i should read back through the data sheet on L387 again before powering up thanks again for help, robb |
troubleshooting method for micro-controller board ? (trying bulb trick)
wrote in message oups.com... On Nov 8, 11:24 am, Eeyore wrote: wrote: On Nov 8, 4:49 am, "Arfa Daily" wrote: Well, I would have to say that it certainly indicates that you are not chasing down any kind of permanent 'short' on your 5v rail. So now that you know where the 5v rail comes off the end of the LM317 (was it ?), can you disconnect it from that point, leave the fuses out of the 12 and 30v feeds, and hook the unit back to line power, with a 5v fuse in place ? Measure the IN, SET and OUT pins of the '317 to see what you get, and if you get a correct 5v on the OUT pin[...] If the voltage isn't correct (e.g. 4.8-5.2V) at that point (but the fuse isn't blown) tack a 470 ohm resistor from the OUT pin to GND. The LM317 has a load regulation spec of 10 mA, and a minimum operating current of ~1mA (for low Vi-Vo); the adjust resistors may not be small enough to draw this much. And don't isolate the regulator by lifting the OUT pin, or you'll lose the adjust resistors. It's not an LM317 though, it's some funny STM part, an L387. Oh. 5mA then, at least if it's the same as the L387A: http://www.st.com/stonline/products/...1337/l387a.pdf It's a fixed 5V regulator, so no Vset resistors. whew , less complications is a welcome occurance to me more good news please thanks, rob |
troubleshooting method for micro-controller board ? (trying bulb trick)
On Nov 8, 3:16 pm, "robb" wrote:
wrote in message ps.com... On Nov 8, 4:49 am, "Arfa Daily" wrote: If the voltage isn't correct (e.g. 4.8-5.2V) at that point (but the fuse isn't blown) tack a 470 ohm resistor from the OUT pin to GND. The LM317 has a load regulation spec of 10 mA, and a minimum operating current of ~1mA (for low Vi-Vo); the adjust resistors may not be small enough to draw this much. And don't isolate the regulator by lifting the OUT pin, or you'll lose the adjust resistors. umm.. i think you lost me,.... yes yes this place is familiar it is "lost land" Ignore all that. 1. As Arfa suggested, isolate the L387 output from the 5V rail. (Probably doesn't matter if you lift Pin 5 or disconnect some other way.) 2. Replace the 5V fuse (and only that fuse? or do you also need the 30V fuse to feed the L387?). 3. Power up. 4. If the fuse didn't blow, measure the voltage from Pin 5 to Pin 3 of the L387 (5V OUT to GND). 5. If you got ~5V, reconnect the 5V rail and test again. If not, connect a 470-1k ohm resistor from Pin 5 to Pin 3 and test again. 6. If still no 5V, measure the voltage from Pin 1 to Pin 3 (Vin to GND) - it should be ~30V. 7. If ~30V was present on Pin 1, the L387 is bad. If not, the 30V bridge is probably bad. 8. If the fuse(s) blew, test the resistance of the bridges. TM |
troubleshooting method for micro-controller board ? (trying bulb trick)
wrote in message oups.com... On Nov 8, 3:16 pm, "robb" wrote: wrote in message ps.com... Ignore all that. 1. As Arfa suggested, isolate the L387 output from the 5V rail. (Probably doesn't matter if you lift Pin 5 or disconnect some other way.) 2. Replace the 5V fuse (and only that fuse? or do you also need the 30V fuse to feed the L387?). 3. Power up. 4. If the fuse didn't blow, measure the voltage from Pin 5 to Pin 3 of the L387 (5V OUT to GND). 5. If you got ~5V, reconnect the 5V rail and test again. If not, connect a 470-1k ohm resistor from Pin 5 to Pin 3 and test again. 6. If still no 5V, measure the voltage from Pin 1 to Pin 3 (Vin to GND) - it should be ~30V. 7. If ~30V was present on Pin 1, the L387 is bad. If not, the 30V bridge is probably bad. 8. If the fuse(s) blew, test the resistance of the bridges. TM thanks TM, i'll try that tonight. thanks, robb |
troubleshooting method for micro-controller board ? (trying bulbtrick)
robb wrote:
"Jamie" t wrote in message ... robb wrote: I have an idea for you. get your self a low voltage auto tail light lamp. use it in place of the fuse that blows. start disconnecting things until the lamp glows dim or not at all. this will allow you to keep the circuit on, you can then track down some heat traces which won't be much.. actually, you'll be able to do a volt tracking using that method.. You might have some logic issues that is causing current to exist only when the circuit is fired up. ok Jamie i tried this idea with a few compromises and tangents I only had 110 v bulbs and lattern light bulbs (~ 6V) so i used my lattern lightbulb and the lattern battery (showing 5.2 Volts) as my power source no components or tracks were wam enough to discern a change after several applications of power with increasing time .... so i inserted the milliAmp meter (the DMM) and that showed ~160 mA with the 6V bulb in series and note the bulb was not shinning as bright as it could. so i removed the bulb and i get ~428 mA without the bulb and the only thing that gets noticeably warm (*but* no more than prior to the ZAP) is the 8051 procesor this same result occurs no matter where along the 5V rail i apply/inject the 5V .... so i am not sure what this means, maybe good news ?? thanks for any help, robb Have you looked at the bridge rectifier and filer cap before your regulator? -- "I'm never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5 |
troubleshooting method for micro-controller board ? (trying bulb trick)
"Jamie" t wrote in message ... robb wrote: "Jamie" t wrote in message ... Have you looked at the bridge rectifier and filer cap before your regulator? yes, that was the first thing i considered just because it was there next to the fuses i desoldered the bridge and then i tested the bridge by using diode tester on the DMM so i chose the combination of pin checks that tests each of the diodes AC1 to (+) .,AC2 to (+), (-) to AC1, (-) to AC2 and each gets ~.596 (+- .007) volts till turn on and there is no "continuity" between aany combo of bridge pins thanks for help and reply, rob |
troubleshooting method for micro-controller board ? (trying bulb trick)
wrote in message oups.com... On Nov 8, 3:16 pm, "robb" wrote: wrote in message ps.com... On Nov 8, 4:49 am, "Arfa Daily" wrote: If the voltage isn't correct (e.g. 4.8-5.2V) at that point (but the fuse isn't blown) tack a 470 ohm resistor from the OUT pin to GND. The LM317 has a load regulation spec of 10 mA, and a minimum operating current of ~1mA (for low Vi-Vo); the adjust resistors may not be small enough to draw this much. And don't isolate the regulator by lifting the OUT pin, or you'll lose the adjust resistors. umm.. i think you lost me,.... yes yes this place is familiar it is "lost land" Ignore all that. 1. As Arfa suggested, isolate the L387 output from the 5V rail. (Probably doesn't matter if you lift Pin 5 or disconnect some other way.) 2. Replace the 5V fuse (and only that fuse? or do you also need the 30V fuse to feed the L387?). 3. Power up. 4. If the fuse didn't blow, measure the voltage from Pin 5 to Pin 3 of the L387 (5V OUT to GND). 5. If you got ~5V, reconnect the 5V rail and test again. If not, connect a 470-1k ohm resistor from Pin 5 to Pin 3 and test again. 6. If still no 5V, measure the voltage from Pin 1 to Pin 3 (Vin to GND) - it should be ~30V. 7. If ~30V was present on Pin 1, the L387 is bad. If not, the 30V bridge is probably bad. 8. If the fuse(s) blew, test the resistance of the bridges. TM Yes. All agreed. This is basically the first set of tests that I was suggesting, which Tony has usefully now converted to specific measurement points for you. Just to try to help you understand the points about the regulators that we were making. Without being too 'blanket', there are two types of linear regulator chips in common use. These are fixed, and variable. The fixed ones are typically three pin, IN - GND -OUT, and come in many different voltages eg 5v 8v 9v 10v 12v 15v and so on. They come in both positive and negative flavours. In general, they don't care too much whether their output pin is loaded or not, but they do have a minimum load figure specified to *guarantee* regulation. Also, disconnecting the output pin from the board, will likely isolate it from a small decoupling cap which will usually be present, and this might, under some circumstances, lead to the regulator oscillating. The variable ones also often have just three pins, such as the LM317, but sometimes have more. The main pins that are generally of any concern, are IN - SET - OUT. The output voltage is determined by a potential divider comprising two resistors, one strung between OUT and SET and the other between SET and the circuit common ground. By altering the ratio of the two resistors, any voltage to within a couple of volts of the input, can be set as the output. Clearly, for this setup to work, the 'top' resistor of the voltage-set divider, *must* remain connected to the output pin. What Tony was saying, is that if you just disconnect the output pin from the board, you will also be disconnecting it from the v-set resistors, which could lead to all manner of nasties ... The good thing about these regulators is that they are pretty bomb-proof. They are safe area protected, short circuit protected and thermally protected, and will go into a voltage foldback condition if any anomalies in their operating conditions are detected. That is not to say that they don't fail themselves. They do. But often, the measured conditions, particularly the parameters measured by the Mk 1 finger-thermometer, are a big clue to what's going on. Example. 5v fixed regulator - say a 7805 1 amp version. Measured output voltage 1.8v. Measured device temperature, using Mk 1 finger = Ouch. Conclusion ? More than an amp is being drawn, the device has overheated, and gone into thermal voltage foldback, to keep within its SOA. Example 2. Same regulator, same set up, same measured ouput voltage. Measured device temperature = cool. Conclusion ? The regulator device itself is faulty. Before there are lots of cries of anguish, a bit simplistic, I know, and yes, there could be other reasons for the measured conditions, but those two examples cover probably 90% of problems around those regulator types. Arfa |
troubleshooting method for micro-controller board ? (trying bulb trick)
wrote in message oups.com... Ignore all that. 1. As Arfa suggested, isolate the L387 output from the 5V rail. (Probably doesn't matter if you lift Pin 5 or disconnect some other way.) 2. Replace the 5V fuse (and only that fuse? or do you also need the 30V fuse to feed the L387?). 3. Power up. 4. If the fuse didn't blow, measure the voltage from Pin 5 to Pin 3 of the L387 (5V OUT to GND). 5. If you got ~5V, reconnect the 5V rail and test again. If not, connect a 470-1k ohm resistor from Pin 5 to Pin 3 and test again. 6. If still no 5V, measure the voltage from Pin 1 to Pin 3 (Vin to GND) - it should be ~30V. 7. If ~30V was present on Pin 1, the L387 is bad. If not, the 30V bridge is probably bad. 8. If the fuse(s) blew, test the resistance of the bridges. TM hi TM, I tested the L387 and i think it must be bad as i get more than 5v from the Vout ? i had already desoldered it from some previous suggestions about isolating the different supply rails so i tested by connecting 5V/1A DC source between Vin and GND-Pin3 and i checked the voltage with DVM between Vout and GND-Pin3 and i was getting 3.47 V i changed to a 18 v/3.5A DC source and i was measuring 8.67 V between Vout and GND-Pin3 L387 is cool and when i connected an LED load to Vout the L387 got very hot very quickly so i suppose i at least need to get an L387 ? thanks again for help, robb |
troubleshooting method for micro-controller board ? (trying bulb trick)
"robb" wrote in message ... wrote in message oups.com... Ignore all that. 1. As Arfa suggested, isolate the L387 output from the 5V rail. (Probably doesn't matter if you lift Pin 5 or disconnect some other way.) 2. Replace the 5V fuse (and only that fuse? or do you also need the 30V fuse to feed the L387?). 3. Power up. 4. If the fuse didn't blow, measure the voltage from Pin 5 to Pin 3 of the L387 (5V OUT to GND). 5. If you got ~5V, reconnect the 5V rail and test again. If not, connect a 470-1k ohm resistor from Pin 5 to Pin 3 and test again. 6. If still no 5V, measure the voltage from Pin 1 to Pin 3 (Vin to GND) - it should be ~30V. 7. If ~30V was present on Pin 1, the L387 is bad. If not, the 30V bridge is probably bad. 8. If the fuse(s) blew, test the resistance of the bridges. TM hi TM, I tested the L387 and i think it must be bad as i get more than 5v from the Vout ? i had already desoldered it from some previous suggestions about isolating the different supply rails so i tested by connecting 5V/1A DC source between Vin and GND-Pin3 and i checked the voltage with DVM between Vout and GND-Pin3 and i was getting 3.47 V i changed to a 18 v/3.5A DC source and i was measuring 8.67 V between Vout and GND-Pin3 L387 is cool and when i connected an LED load to Vout the L387 got very hot very quickly so i suppose i at least need to get an L387 ? thanks again for help, robb From that, it sounds as though the '387 is not doing its job correctly, so replacing it would probably be a good move. Arfa |
troubleshooting method for micro-controller board ? (trying bulb trick)
"Arfa Daily" wrote in message ... wrote in message oups.com... On Nov 8, 3:16 pm, "robb" wrote: wrote in message ps.com... Yes. All agreed. This is basically the first set of tests that I was suggesting, which Tony has usefully now converted to specific measurement points for you. Just to try to help you understand the points about the regulators that we were making. Without being too 'blanket', there are two types of linear regulator chips in common use. These are fixed, and variable. The fixed ones are typically three pin, IN - GND -OUT, and come in many different voltages eg 5v 8v 9v 10v 12v 15v and so on. They come in both positive and negative flavours. In general, they don't care too much whether their output pin is loaded or not, but they do have a minimum load figure specified to *guarantee* regulation. Also, disconnecting the output pin from the board, will likely isolate it from a small decoupling cap which will usually be present, and this might, under some circumstances, lead to the regulator oscillating. The variable ones also often have just three pins, such as the LM317, but sometimes have more. The main pins that are generally of any concern, are IN - SET - OUT. The output voltage is determined by a potential divider comprising two resistors, one strung between OUT and SET and the other between SET and the circuit common ground. By altering the ratio of the two resistors, any voltage to within a couple of volts of the input, can be set as the output. Clearly, for this setup to work, the 'top' resistor of the voltage-set divider, *must* remain connected to the output pin. What Tony was saying, is that if you just disconnect the output pin from the board, you will also be disconnecting it from the v-set resistors, which could lead to all manner of nasties ... The good thing about these regulators is that they are pretty bomb-proof. They are safe area protected, short circuit protected and thermally protected, and will go into a voltage foldback condition if any anomalies in their operating conditions are detected. That is not to say that they don't fail themselves. They do. But often, the measured conditions, particularly the parameters measured by the Mk 1 finger-thermometer, are a big clue to what's going on. Example. 5v fixed regulator - say a 7805 1 amp version. Measured output voltage 1.8v. Measured device temperature, using Mk 1 finger = Ouch. Conclusion ? More than an amp is being drawn, the device has overheated, and gone into thermal voltage foldback, to keep within its SOA. Example 2. Same regulator, same set up, same measured ouput voltage. Measured device temperature = cool. Conclusion ? The regulator device itself is faulty. Before there are lots of cries of anguish, a bit simplistic, I know, and yes, there could be other reasons for the measured conditions, but those two examples cover probably 90% of problems around those regulator types. Arfa Hi Arfa, thanks for all the useful help and iinformatin i really do appreciate your's and everyones helpful advice and information. I started this project as a learning exercise guess its more a workout. Regarding the L387, since i had already removed it hat was asy to test. I am pretty sure it is bad from what you explained. that is 5V regulators only output 5V . when i applied a 5V/1A DC source to Vin/GND i measured 3.47V between Vout/GND. when i applied a 18 V / 3.5A DC source to the Vin/GND i measured 8.37V between Vout/GND an LED load between Vout/GND caused the L387 to get very hot quickly. so a new L387 is in order so that i can complete the other tests that you TM and others have suggested thanks again for help, robb |
troubleshooting method for micro-controller board ? (trying bulbtrick)
Arfa Daily wrote: "robb" wrote in message I tested the L387 and i think it must be bad as i get more than 5v from the Vout ? How much more ? A couple of hundred millivolts, says 5.25 V is OK. i had already desoldered it from some previous suggestions about isolating the different supply rails so i tested by connecting 5V/1A DC source between Vin and GND-Pin3 and i checked the voltage with DVM between Vout and GND-Pin3 and i was getting 3.47 V Pointless. It won't operate correctly with only 5V in. 3.47V is sort of what I'd expect under those conditions. A linear voltage regulator has to have several volts more on the input than the output to function correctly. i changed to a 18 v/3.5A DC source and i was measuring 8.67 V between Vout and GND-Pin3 L387 is cool and when i connected an LED load to Vout the L387 got very hot very quickly so i suppose i at least need to get an L387 ? What value resistor did you have in series with the LED ? From that, it sounds as though the '387 is not doing its job correctly, so replacing it would probably be a good move. He didn't say if he had a resistor in series with the LED ! Could explain a lot. Graham |
troubleshooting method for micro-controller board ? (trying bulbtrick)
robb wrote: Regarding the L387, since i had already removed it hat was asy to test. I am pretty sure it is bad from what you explained. that is 5V regulators only output 5V . when i applied a 5V/1A DC source to Vin/GND i measured 3.47V between Vout/GND. when i applied a 18 V / 3.5A DC source to the Vin/GND i measured 8.37V between Vout/GND With a load or no load ? If there was no load on the regulator output then that's quite possible even for a good L387. You must have a load resistor of around 470 ohms on the 5V output for testing for the chip to regulate properly. an LED load between Vout/GND caused the L387 to get very hot quickly. An LED with no series current limiting resistor might well do that ! You should have a resistor of ~ 150 ohms in series with the LED. so a new L387 is in order so that i can complete the other tests that you TM and others have suggested It may not be necessary. Your testing used flawed methods. Graham |
troubleshooting method for micro-controller board ? (trying bulb trick)
"Eeyore" wrote in message ... Arfa Daily wrote: "robb" wrote in message so i tested by connecting 5V/1A DC source between Vin and GND-Pin3 and i checked the voltage with DVM between Vout and GND-Pin3 and i was getting 3.47 V Pointless. It won't operate correctly with only 5V in. 3.47V is sort of what I'd expect under those conditions. A linear voltage regulator has to have several volts more on the input than the output to function correctly. hi graham, just being cautious and i do not have much in the way of handy power sources, various wall warts. i changed to a 18 v/3.5A DC source and i was measuring 8.67 V between Vout and GND-Pin3 L387 is cool and when i connected an LED load to Vout the L387 got very hot very quickly so i suppose i at least need to get an L387 ? What value resistor did you have in series with the LED ? you need to use a resistor ??? just joking it was 100 Ohm 1/2 watt (Brwn Blk Brwn Gold) would you expect 8.67 Vout with 18V DC Vinput ? thanks for help, robb |
troubleshooting method for micro-controller board ? (trying bulb trick)
"Eeyore" wrote in message ... robb wrote: Regarding the L387, since i had already removed it hat was asy to test. I am pretty sure it is bad from what you explained. that is 5V regulators only output 5V . when i applied a 5V/1A DC source to Vin/GND i measured 3.47V between Vout/GND. when i applied a 18 V / 3.5A DC source to the Vin/GND i measured 8.37V between Vout/GND With a load or no load ? If there was no load on the regulator output then that's quite possible even for a good L387. You must have a load resistor of around 470 ohms on the 5V output for testing for the chip to regulate properly. ok, i set it up as you suggest a 470 Ohms between Vout and GND (Pin3) with 16v/3A DC source connected to Vin and GRD. The measurement between Vout and GND was 8.03 V when i put a LED in series with 470Ohms i get 7.92 V measured accross Vout and GND. It may not be necessary. Your testing used flawed methods. that is why i am seeking help from "the group", "the fountain" of electronic knowledge :( thanks for help graham, robb |
troubleshooting method for micro-controller board ? (trying bulbtrick)
robb wrote: "Eeyore" wrote What value resistor did you have in series with the LED ? you need to use a resistor ??? just joking it was 100 Ohm 1/2 watt (Brwn Blk Brwn Gold) would you expect 8.67 Vout with 18V DC Vinput ? Not under those conditions. You do need a new L387. Graham |
troubleshooting method for micro-controller board ? (trying bulb trick)
On Nov 9, 4:17 am, "Arfa Daily" wrote:
"robb" wrote in message ... wrote in message roups.com... Ignore all that. 1. As Arfa suggested, isolate the L387 output from the 5V rail. (Probably doesn't matter if you lift Pin 5 or disconnect some other way.) 2. Replace the 5V fuse (and only that fuse? or do you also need the 30V fuse to feed the L387?). 3. Power up. 4. If the fuse didn't blow, measure the voltage from Pin 5 to Pin 3 of the L387 (5V OUT to GND). 5. If you got ~5V, reconnect the 5V rail and test again. If not, connect a 470-1k ohm resistor from Pin 5 to Pin 3 and test again. 6. If still no 5V, measure the voltage from Pin 1 to Pin 3 (Vin to GND) - it should be ~30V. 7. If ~30V was present on Pin 1, the L387 is bad. If not, the 30V bridge is probably bad. 8. If the fuse(s) blew, test the resistance of the bridges. TM hi TM, I tested the L387 and i think it must be bad as i get more than 5v from the Vout ? i had already desoldered it from some previous suggestions about isolating the different supply rails so i tested by connecting 5V/1A DC source between Vin and GND-Pin3 and i checked the voltage with DVM between Vout and GND-Pin3 and i was getting 3.47 V i changed to a 18 v/3.5A DC source and i was measuring 8.67 V between Vout and GND-Pin3 L387 is cool and when i connected an LED load to Vout the L387 got very hot very quickly so i suppose i at least need to get an L387 ? thanks again for help, robb From that, it sounds as though the '387 is not doing its job correctly, so replacing it would probably be a good move. So while you're waiting for the new L387 (or better yet, before you even order it), replace the 30V and 12V fuses, connect your (5.2V) lantern battery to the 5V rail, and power up. Does the board work? Fuses blow? 30V and 12V rails measure OK? TM |
troubleshooting method for micro-controller board ? (trying bulb trick)
On Nov 9, 4:36 am, Eeyore
wrote: "robb" wrote in message so i tested by connecting 5V/1A DC source between Vin and GND-Pin3 and i checked the voltage with DVM between Vout and GND-Pin3 and i was getting 3.47 V Pointless. It won't operate correctly with only 5V in. Agreed. A linear voltage regulator has to have several volts more on the input than the output to function correctly. Some need 1-2V more, others around 1/2V (I think I've seen LDOs down to 0.2V dropout [i.e. Vout-Vin]). I didn't find a spec sheet for the L387, but the L387A has a max dropout of 0.8V (and that's from 4.9V, so Vin[min] is 5.7V). Don't know whether dropout is one of the improvements in the A version. In most cases it's safe to test with Vin=Vout+2V, but with an adjustable LDO operating near the top of the Vout range, that may result in Vin exceeding spec. Checking the data sheet first is always a good idea. (LDO = Low DropOut, a category of linear regulator) TM |
troubleshooting method for micro-controller board ? (trying bulbtrick)
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