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troubleshooting method for micro-controller board ?

E

Eeyore

Jan 1, 1970
0
Jamie said:
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
 
J

Jamie

Jan 1, 1970
0
Eeyore said:
Jamie wrote:




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!
 
E

Eeyore

Jan 1, 1970
0
Jamie said:
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 FUCKING IDIOT.

DON'T UPSET THE OP'S ATTEMPS TO FIX HIS PROBLEM WITH YOUR USELESS SHIITY IDEAS.

Graham
 
J

James Sweet

Jan 1, 1970
0
robb said:
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.
 
J

Jamie

Jan 1, 1970
0
Eeyore said:
Jamie wrote:




YOU'RE A FUCKING 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 shit 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?
 
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
 
R

robb

Jan 1, 1970
0
Jamie said:
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
 
R

robb

Jan 1, 1970
0
Eeyore said:
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
 
J

James Sweet

Jan 1, 1970
0
robb said:
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?
 
A

Arfa Daily

Jan 1, 1970
0
robb said:
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
 
E

Eeyore

Jan 1, 1970
0
robb said:
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
 
E

Eeyore

Jan 1, 1970
0
James said:
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
 
R

robb

Jan 1, 1970
0
Eeyore said:
I seem to recall that the NMOS versions (which he has) draw a little over 100mA.

Graham

the datasheet says 125 mA dissipates 1W
 
E

Eeyore

Jan 1, 1970
0
robb said:
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
 
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
 
R

robb

Jan 1, 1970
0
Eeyore said:
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
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
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
 
E

Eeyore

Jan 1, 1970
0
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.

Graham
 
R

robb

Jan 1, 1970
0
Arfa Daily said:
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
 
I

ian field

Jan 1, 1970
0
robb said:
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!
 
A

Arfa Daily

Jan 1, 1970
0
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
 
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