troubleshooting method for micro-controller board ?

it

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

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!

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

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

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

the L298s

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?

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

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

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

Lucky that 6V is *just* acceptable.

You mean when you apply the battery directly to the 5V line ?

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

I seem to recall that the NMOS versions (which he has) draw a little over 100mA.

Graham

enough heat to

little over 100mA.

the datasheet says 125 mA dissipates 1W

Graham

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

flashlight

:) hi Graham, now i have learned a wee bit

I pre-checked battery it was slightly drained and only showing

shows

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

- 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

than

range.

the one you have

power peripherals

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

It's not an LM317 though, it's some funny STM part, an L387.

Graham

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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

Its phutted!

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

Oh. 5mA then, at least if it's the same as the L387A:

TM

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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