Need a little bit of help.

D

dave

Guest
Need a little bit of help.

Did a project kit, the velleman-kit K8048, a PIC Programmer
and Experimentation Board.

The first thing I did wrong was to solder in the 2 voltage regulators
the wrong way round and then connect a regulated power supply when it
should have been an unregulated one.

I desoldered the VR's and replaced with new ones.
I purchased an unregulated psu and connected it, but nothing
seems to work (no LEDs coming on). When I touch the first
voltage regulator it becomes hotter and hotter. I pull out the PSU
before it fries.

Can anyone suggest what could be wrong?


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On Thu, 21 Apr 2005 21:49:46 GMT, in sci.electronics.design "dave"
<newbie@newbie.com> wrote:

Need a little bit of help.

Did a project kit, the velleman-kit K8048, a PIC Programmer
and Experimentation Board.

The first thing I did wrong was to solder in the 2 voltage regulators
the wrong way round and then connect a regulated power supply when it
should have been an unregulated one.

I desoldered the VR's and replaced with new ones.
I purchased an unregulated psu and connected it, but nothing
seems to work (no LEDs coming on). When I touch the first
voltage regulator it becomes hotter and hotter. I pull out the PSU
before it fries.

Can anyone suggest what could be wrong?


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Click to expand...
It sounds like the "Dead parrot" sketch.
You've probablly blown any micro's etc on the board.

What test equpment do you have ?


martin

After the first death, there is no other.
(Dylan Thomas)
 
On Thu, 21 Apr 2005 21:49:46 GMT, "dave" <newbie@newbie.com> wrote:

Need a little bit of help.

Did a project kit, the velleman-kit K8048, a PIC Programmer
and Experimentation Board.

The first thing I did wrong was to solder in the 2 voltage regulators
the wrong way round and then connect a regulated power supply when it
should have been an unregulated one.
Click to expand...
The regulated versus unregulated part probaby didn't have any affect
on this.

I desoldered the VR's and replaced with new ones.
I purchased an unregulated psu and connected it, but nothing
seems to work (no LEDs coming on). When I touch the first
voltage regulator it becomes hotter and hotter. I pull out the PSU
before it fries.
Click to expand...
Something on the side of the circuit fed by the first VR got hurt, and
too much current is being drawn. This will require troubleshooting.
How many active components are being fed by that supply? You may get
lucky.

One way you might try to troubleshoot this is to disconnect the power
supply feed to every active component, then do an ohms check on each
disconnected power feed. Very low ohms could indicate a
short/low-resistance shunt.

What voltages, +/-5?

Tom
 
Hello Tom,

One way you might try to troubleshoot this is to disconnect the power
supply feed to every active component, then do an ohms check on each
disconnected power feed. Very low ohms could indicate a
short/low-resistance shunt.
Click to expand...
In the olden days with lots of parts on the boards there was another way
but I certainly will not recommend that: Don safety goggles, apply the
correct regulated VCC from a really stiff power supply and see what gets
hot or smokes out...

Regards, Joerg

http://www.analogconsultants.com
 
"dave" <newbie@newbie.com> wrote in message
news:_dV9e.2016$TT6.695@newsfe3-win.ntli.net...
Need a little bit of help.

Did a project kit, the velleman-kit K8048, a PIC Programmer
and Experimentation Board.

The first thing I did wrong was to solder in the 2 voltage regulators
the wrong way round and then connect a regulated power supply when it
should have been an unregulated one.

I desoldered the VR's and replaced with new ones.
I purchased an unregulated psu and connected it, but nothing
seems to work (no LEDs coming on). When I touch the first
voltage regulator it becomes hotter and hotter. I pull out the PSU
before it fries.

Can anyone suggest what could be wrong?

Does anything else get hot? Something is obviously drawing way too much
Click to expand...
current, so it should be getting hot too. If not you may have a short
circuit on your supply.

Get a voltmeter and check the input and output voltages on those regulator
chips. If you can disconnect the output of the regulators easily do so and
check the output voltages again. Is there a copy of the circuit you can
point us to?

Cheers.

Ken
 
Hello Ken,

Get a voltmeter and check the input and output voltages on those regulator
chips. If you can disconnect the output of the regulators easily do so and
check the output voltages again. Is there a copy of the circuit you can
point us to?
Click to expand...
With a DVM it is also possible to measure voltage drops and pinpoint the
culprit. We have even done it on boards with full power and ground
planes, to within less than a square-inch of where the short actually
was. Compared to the brute force method (leave power on until something
gives up) this can avoid burning out vias.

Regards, Joerg

http://www.analogconsultants.com
 
Ken Taylor wrote:
"dave" <newbie@newbie.com> wrote in message
news:_dV9e.2016$TT6.695@newsfe3-win.ntli.net...

Need a little bit of help.

Did a project kit, the velleman-kit K8048, a PIC Programmer
and Experimentation Board.

The first thing I did wrong was to solder in the 2 voltage regulators
the wrong way round and then connect a regulated power supply when it
should have been an unregulated one.

I desoldered the VR's and replaced with new ones.
I purchased an unregulated psu and connected it, but nothing
seems to work (no LEDs coming on). When I touch the first
voltage regulator it becomes hotter and hotter. I pull out the PSU
before it fries.

Can anyone suggest what could be wrong?


Does anything else get hot? Something is obviously drawing way too much
current, so it should be getting hot too. If not you may have a short
circuit on your supply.

Get a voltmeter and check the input and output voltages on those regulator
chips. If you can disconnect the output of the regulators easily do so and
check the output voltages again. Is there a copy of the circuit you can
point us to?

Cheers.

Ken


Hi,
Click to expand...

The parts that are already shorted do not tend to heat up. Instead, they
cause other parts to heat up. All of this leads to a "Night of the
Living Dead" scenerio where dead parts come back to consume the living.


--
Luhan Monat (luhanis 'at' yahoo 'dot' com)
"The future is not what it used to be..."
http://members.cox.net/berniekm
 
"Luhan Monat" <x@y.z> wrote in message
news:5lX9e.8223$EX4.4816@fed1read01...
Ken Taylor wrote:
"dave" <newbie@newbie.com> wrote in message
news:_dV9e.2016$TT6.695@newsfe3-win.ntli.net...

Need a little bit of help.

Did a project kit, the velleman-kit K8048, a PIC Programmer
and Experimentation Board.

The first thing I did wrong was to solder in the 2 voltage regulators
the wrong way round and then connect a regulated power supply when it
should have been an unregulated one.

I desoldered the VR's and replaced with new ones.
I purchased an unregulated psu and connected it, but nothing
seems to work (no LEDs coming on). When I touch the first
voltage regulator it becomes hotter and hotter. I pull out the PSU
before it fries.

Can anyone suggest what could be wrong?


Does anything else get hot? Something is obviously drawing way too much
current, so it should be getting hot too. If not you may have a short
circuit on your supply.

Get a voltmeter and check the input and output voltages on those
regulator
chips. If you can disconnect the output of the regulators easily do so
and
check the output voltages again. Is there a copy of the circuit you can
point us to?

Cheers.

Ken


Hi,

The parts that are already shorted do not tend to heat up. Instead, they
cause other parts to heat up. All of this leads to a "Night of the
Living Dead" scenerio where dead parts come back to consume the living.


--
Luhan Monat (luhanis 'at' yahoo 'dot' com)
"The future is not what it used to be..."
http://members.cox.net/berniekm
Click to expand...
You're right, but they may heat up (they may not be a complete short), so
with an OP who is clearly a novice it's worth a try. But reaching for the
meter will be even better of course.

And I love the 'scenario'. :-

Cheers.

Ken
 
Thanks to everyone for your advice. I'm just learning about electronics, but I will use all
your advice as a starting point.

I didn't have any PIC chip connected when I first switched it on, so maybe the PIC survived.

I do have a schematic here (not very clear), but I guess it works, otherwise they would sell it (or would they?).

http://us.f2.yahoofs.com/bc/4268ca17_14a69/bc/My+Documents/pic+programmer+schematic.gif?bfK6MaCBHFa8E5bf




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I read in sci.electronics.design that dave <newbie@newbie.com> wrote (in
<tW3ae.288$5A3.37@newsfe4-win.ntli.net>) about 'Need a little bit of
help.', on Fri, 22 Apr 2005:
I do have a schematic here (not very clear), but I guess it works,
otherwise they would sell it (or would they?).

http://us.f2.yahoofs.com/bc/4268ca17_14a69/bc/My+Documents/pic+programme
r+schematic.gif?bfK6MaCBHFa8E5bf
Click to expand...
You bet people would! And I can't get the page; it's a 404.
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
'What is a Moebius strip?'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
 
Sorry about that page link, damn useless yahoo briefcase.

Here's another link:
http://homepage.ntlworld.com/davidsallows2004/

I invested some money in a new multimeter and tested all the diodes. A bank of 6 LEDs seem
to be non-functional. The rest of the diodes are okay. I'll replace the LEDs and see what happens.

By the way, the multimeter I bought it new from Maplin. A Mastech MAS-343. A few years ago, it was 70 pounds. I got it today for 20 pounds. I guess this is a good deal. Looks like a good multimeter to me.



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"dave" <newbie@newbie.com> wrote in message
news:qpbae.2474$TT6.1960@newsfe3-win.ntli.net...
Sorry about that page link, damn useless yahoo briefcase.

Here's another link:
http://homepage.ntlworld.com/davidsallows2004/

I invested some money in a new multimeter and tested all the diodes. A
bank of 6 LEDs seem
to be non-functional. The rest of the diodes are okay. I'll replace the
LEDs and see what happens.

By the way, the multimeter I bought it new from Maplin. A Mastech
MAS-343. A few years ago, it was 70 pounds. I got it today for 20 pounds.
Click to expand...
I guess this is a good deal. Looks like a good multimeter to me.
Looks good to me too. Nice buy. I don't see why LED's 1-6 would be faulty if
Click to expand...
you didn't have the PIC in circuit. If the meter has a diode test function
on it (I couldn't tell from the blurry pic I saw of one) use that to test
them, or failing that just use a 9V battery and a 330 Ohm resistor in
series. LD9 is a bit problematic - if it really is wired as shown it'll blow
as it is straight across the 5V. I think it's probably meant to be in series
with the resistor shown next to it, but that's marked as a higher value than
I would have expected if that was the case. Unless it is an LED meant to run
off 5V - is it a different type than the others?

Let us know the voltage at point VR1 (output of first reg) and also the 5V
rail. Also check for shorts (solder dags in particular around the
regulators).

Cheers.

Ken
 
Well, looks like I had most of the LEDs inserted the wrong way round. Don't know my
anode from my cathode. I'm learning the hard way.



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dave wrote:

Well, looks like I had most of the LEDs inserted the wrong way round.
Don't know my
anode from my cathode. I'm learning the hard way.
Click to expand...
By looking in the "glass" of the LED, you normally see two connectors
inside: A huge one and a much smaller one. The huge one is the cathode:
This is where you connect the more negative potential, normally the ground.

Looking inside the "glass" of the LED is a good way to distinguish anode
from cathode even if the wires are shortend.
 
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