lm317?

Google Groups
1

Do we have some lm317 at the lab? The one I pulled out of my bits bin
appears to have seen better days. I don’t think it’s regulating at all.
Instead of 10v I get 18 lol

2

Have you got the voltage selector pin set properly? If I remember rightly
its 1.25v at 20ma or so. Double check your calculations and resistors.
Alex can probably elaborate a bit more…On 24 Oct 2013 22:06, “Steven Choi” swchoi.choi@gmail.com wrote:

Do we have some lm317 at the lab? The one I pulled out of my bits bin
appears to have seen better days. I don’t think it’s regulating at all.
Instead of 10v I get 18 lol

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3

Steve

Need to see your circuit to help. Tom is correct though. Say Input voltage
is 20V. Reference pin will be as Tom said at 1.25V. Output should be at the
voltage division you set down to 1.25 min. Is lm317 hot? If 18V output
input must be at that value or more. Check for shorts etc.

We do have some at the space if you need one.

AlexOn 24 Oct 2013 22:21, “Tom Bloor” tom.bloor@gmail.com wrote:

Have you got the voltage selector pin set properly? If I remember rightly
its 1.25v at 20ma or so. Double check your calculations and resistors.
Alex can probably elaborate a bit more…
On 24 Oct 2013 22:06, “Steven Choi” swchoi.choi@gmail.com wrote:

Do we have some lm317 at the lab? The one I pulled out of my bits bin
appears to have seen better days. I don’t think it’s regulating at all.
Instead of 10v I get 18 lol

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4

I can only.assume its dead.because.the website I.used to check the resistors applies for lm317 as well as lm338 . I used a known working lm338 and it works. I get 10v. also if u mean the adjustment pin it was putting out 18v I believe. if I understood correctly it should always have 1.25v that is why u.can’t get true zero volts output without some.extra circuitry. I will double check perhaps I wasn’t measuring with respect to gnd.
unless am being.a tool againAlexander Lang alexanderlang1980@gmail.com wrote:

Steve

Need to see your circuit to help. Tom is correct though. Say Input voltage
is 20V. Reference pin will be as Tom said at 1.25V. Output should be at the
voltage division you set down to 1.25 min. Is lm317 hot? If 18V output
input must be at that value or more. Check for shorts etc.

We do have some at the space if you need one.

Alex
On 24 Oct 2013 22:21, “Tom Bloor” tom.bloor@gmail.com wrote:

Have you got the voltage selector pin set properly? If I remember rightly
its 1.25v at 20ma or so. Double check your calculations and resistors.
Alex can probably elaborate a bit more…
On 24 Oct 2013 22:06, “Steven Choi” swchoi.choi@gmail.com wrote:

Do we have some lm317 at the lab? The one I pulled out of my bits bin
appears to have seen better days. I don’t think it’s regulating at all.
Instead of 10v I get 18 lol

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5

Lm338 is the same as an lm317, just it can give out more current and a
higher input…if it worked keep using it.

AlexOn 25 Oct 2013 06:47, “gmail” swchoi.choi@gmail.com wrote:

I can only.assume its dead.because.the website I.used to check the
resistors applies for lm317 as well as lm338 . I used a known working lm338
and it works. I get 10v. also if u mean the adjustment pin it was putting
out 18v I believe. if I understood correctly it should always have 1.25v
that is why u.can’t get true zero volts output without some.extra
circuitry. I will double check perhaps I wasn’t measuring with respect to
gnd.
unless am being.a tool again

Alexander Lang alexanderlang1980@gmail.com wrote:

Steve

Need to see your circuit to help. Tom is correct though. Say Input voltage
is 20V. Reference pin will be as Tom said at 1.25V. Output should be at
the
voltage division you set down to 1.25 min. Is lm317 hot? If 18V output
input must be at that value or more. Check for shorts etc.

We do have some at the space if you need one.

Alex
On 24 Oct 2013 22:21, “Tom Bloor” tom.bloor@gmail.com wrote:

Have you got the voltage selector pin set properly? If I remember
rightly

its 1.25v at 20ma or so. Double check your calculations and resistors.
Alex can probably elaborate a bit more…
On 24 Oct 2013 22:06, “Steven Choi” swchoi.choi@gmail.com wrote:

Do we have some lm317 at the lab? The one I pulled out of my bits bin
appears to have seen better days. I don’t think it’s regulating at all.
Instead of 10v I get 18 lol

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