I need an helb but.........

S

Slang

Guest
..........i don't know if i am in the right place.
I have an apparatus that is fed with 12 volts cc: a Linear IC (LT1940
1.1 MHz step-down switching regulator, with some external components)
supplies two different voltages lines, 5 and 3 V. One of these two lines
feeds a microprocessor and some RAM memories.
I can see some problems with the CPU, so i would like to verify the
linearity of the feed that goes to it. I think that an oscilloscope is
indispensable, but who can explain me the way to do this?
Thanks and forgive my bad english.
Slang
 
Slang <fra.gui_NS_@tin.it> writes:

.........i don't know if i am in the right place.
I have an apparatus that is fed with 12 volts cc: a Linear IC (LT1940
1.1 MHz step-down switching regulator, with some external components)
supplies two different voltages lines, 5 and 3 V. One of these two
lines feeds a microprocessor and some RAM memories.
I can see some problems with the CPU, so i would like to verify the
linearity of the feed that goes to it. I think that an oscilloscope is
indispensable, but who can explain me the way to do this?
Thanks and forgive my bad english.
Slang
Click to expand...
The first thing to do is verify that the 5 V and 3 V lines have
the correct voltage. This can be done with a multimeter. The next
thing would be to check for noise on these lines, but that will
require an oscilloscope.

--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
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Samuel M. Goldwasser ha scritto:
Slang <fra.gui_NS_@tin.it> writes:

.........i don't know if i am in the right place.
I have an apparatus that is fed with 12 volts cc: a Linear IC (LT1940
1.1 MHz step-down switching regulator, with some external components)
supplies two different voltages lines, 5 and 3 V. One of these two
lines feeds a microprocessor and some RAM memories.
I can see some problems with the CPU, so i would like to verify the
linearity of the feed that goes to it. I think that an oscilloscope is
indispensable, but who can explain me the way to do this?
Thanks and forgive my bad english.
Slang

The first thing to do is verify that the 5 V and 3 V lines have
the correct voltage. This can be done with a multimeter. The next
thing would be to check for noise on these lines, but that will
require an oscilloscope.

--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.
Click to expand...
Thank you for your answer.
I already checked voltages and them are ok.
I know i need an oscilloscope.
Considering the IC and its switching frequencies, what kind of
oscilloscope do i need? Is a "20 Mhz band" enough?
And what is the procedute to test the circuit with the oscilloscope?
Thank you for your patience.
Slang
 
Slang <fra.gui_NS_@tin.it> writes:

Samuel M. Goldwasser ha scritto:
Slang <fra.gui_NS_@tin.it> writes:

.........i don't know if i am in the right place.
I have an apparatus that is fed with 12 volts cc: a Linear IC (LT1940
1.1 MHz step-down switching regulator, with some external components)
supplies two different voltages lines, 5 and 3 V. One of these two
lines feeds a microprocessor and some RAM memories.
I can see some problems with the CPU, so i would like to verify the
linearity of the feed that goes to it. I think that an oscilloscope is
indispensable, but who can explain me the way to do this?
Thanks and forgive my bad english.
Slang
The first thing to do is verify that the 5 V and 3 V lines have
the correct voltage. This can be done with a multimeter. The next
thing would be to check for noise on these lines, but that will
require an oscilloscope.
--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/

Thank you for your answer.
I already checked voltages and them are ok.
I know i need an oscilloscope.
Considering the IC and its switching frequencies, what kind of
oscilloscope do i need? Is a "20 Mhz band" enough?
And what is the procedute to test the circuit with the oscilloscope?
Thank you for your patience.
Slang
Click to expand...
Maybe start by describing what problems you are seeing with the CPU, etc.

As far as scope bandwidth, it's going to depend on what you're looking
for. A 20 MHz scope won't be much use in looking at 100 MHz busses.
But if you're just looking for noise on the power lines, it may suffice.

But, realistically, trying to give you a crash course in complex digital
system troubleshooting, is not something that's likely to be very effective
via a forum such as this.

--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.
 
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