[Eeyore]

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

[Jamie]

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

[Eeyore]

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

[James Sweet]

"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.

[Jamie]

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

[[email protected]]

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

[robb]

"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

[robb]

"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

[James Sweet]

"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?

[Arfa Daily]

"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

[Eeyore]

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

[Eeyore]

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

[robb]

"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

[Eeyore]

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

[[email protected]]

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

[robb]

"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

[Eeyore]

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.

Graham

[robb]

"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

[ian field]

"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!

[Arfa Daily]

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

[[email protected]]

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

[robb]

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

[robb]

"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

[robb]

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

[[email protected]]

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

[robb]

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

[Jamie]

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

[robb]

"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

[Arfa Daily]

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

[robb]

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

[Arfa Daily]

"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

[robb]

"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

[Eeyore]

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

[Eeyore]

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

[robb]

"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

[robb]

"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

[Eeyore]

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

[[email protected]]

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

[[email protected]]

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

[Eeyore]

wrote:

Eeyore wriote:
"robb" wrote :

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]).

Sure, I was generalising somewhat for brevity.

As you say the value may vavy from several hundred millivolts for true LDO types
to as much as 3V in rare cases. 2V is typically a safe value to ensure correct
operation.

Graham