Hi Everybody

This chip normally puts out square pulses. In the power supply I am
working on (http://www.laserfaq.org/sam/150rcsch.pdf) it is putting
out a sawtooth wave. I am testing it in 'standby mode', in which Q4 is
off and R33 is in control of the duty cycle. Replacing the IC1 has no
effect. Does anyone have any ideas?

On Jul 2, 3:35 pm, alphamnemonic wrote:
Hi Everybody

This chip normally puts out square pulses. In the power supply I am
working on (http://www.laserfaq.org/sam/150rcsch.pdf) it is putting
out a sawtooth wave. I am testing it in 'standby mode', in which Q4 is
off and R33 is in control of the duty cycle. Replacing the IC1 has no
effect. Does anyone have any ideas?

Where are you seeing sawtooths? Pin 13?

--- 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.

wrote in news:16ea6110-be19-4a21-aecc-
:

On Jul 2, 3:35 pm, alphamnemonic wrote:
Hi Everybody

This chip normally puts out square pulses. In the power supply I am
working on (http://www.laserfaq.org/sam/150rcsch.pdf) it is putting
out a sawtooth wave. I am testing it in 'standby mode', in which Q4 is
off and R33 is in control of the duty cycle. Replacing the IC1 has no
effect. Does anyone have any ideas?

Where are you seeing sawtooths? Pin 13?

--- 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.


That is my question. Why do you have output A and output B (pin 11 and 14)
grounded?

Also, pin 13 is VC in for the transistor collectors. Why do you have this
connected as an output?

On Jul 2, 6:20*pm, Steve wrote:
wrote in news:16ea6110-be19-4a21-aecc-
:





On Jul 2, 3:35 pm, alphamnemonic wrote:
Hi Everybody

This chip normally puts out square pulses. In the power supply I am
working on (http://www.laserfaq.org/sam/150rcsch.pdf) it is putting
out a sawtooth wave. I am testing it in 'standby mode', in which Q4 is
off and R33 is in control of the duty cycle. Replacing the IC1 has no
effect. Does anyone have any ideas?

Where are you seeing sawtooths? *Pin 13?

--- 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.

That is my question. Why do you have output A and output B (pin 11 and 14)
grounded?

Also, pin 13 is VC in for the transistor collectors. Why do you have this
connected as an output?- Hide quoted text -

- Show quoted text -

Yes the sawtooth is on pin 13. Pin 13 is being used as an output and
pins 11 and 14 are grounded because the chip is being used in single-
ended supply mode (see http://www.datasheetcatalog.org/data...a/SG3525AN.pdf
p.6 for an example of this configuration). I can see why you find that
strange--I did too!

alphamnemonic wrote in
:

On Jul 2, 6:20*pm, Steve wrote:
wrote in news:16ea6110-be19-4a21-aecc-
:





On Jul 2, 3:35 pm, alphamnemonic wrote:
Hi Everybody

This chip normally puts out square pulses. In the power supply I
am working on (http://www.laserfaq.org/sam/150rcsch.pdf) it is
putting out a sawtooth wave. I am testing it in 'standby mode', in
which Q4 is off and R33 is in control of the duty cycle. Replacing
the IC1 has no effect. Does anyone have any ideas?

Where are you seeing sawtooths? *Pin 13?

--- 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.

That is my question. Why do you have output A and output B (pin 11
and 14
)
grounded?

Also, pin 13 is VC in for the transistor collectors. Why do you have
this connected as an output?- Hide quoted text -

- Show quoted text -

Yes the sawtooth is on pin 13. Pin 13 is being used as an output and
pins 11 and 14 are grounded because the chip is being used in single-
ended supply mode (see
http://www.datasheetcatalog.org/data...a/SG3525AN.pdf p.6
for an example of this configuration). I can see why you find that
strange--I did too!


I'd avoid the funky setup you have. In my opinion I'd connect pin 13 and 15
together and use either output A or B.

I'm not sure what Q4 is doing, I've never seen it used this way, but you
must know more than me since you designed this elaborte circuit.


Keep us posted at what you do to resolve the problem.

On Jul 3, 6:09*pm, Steve wrote:
alphamnemonic wrote :





On Jul 2, 6:20*pm, Steve wrote:
wrote in news:16ea6110-be19-4a21-aecc-
:

On Jul 2, 3:35 pm, alphamnemonic wrote:
Hi Everybody

This chip normally puts out square pulses. In the power supply I
am working on (http://www.laserfaq.org/sam/150rcsch.pdf) it is
putting out a sawtooth wave. I am testing it in 'standby mode', in
which Q4 is off and R33 is in control of the duty cycle. Replacing
the IC1 has no effect. Does anyone have any ideas?

Where are you seeing sawtooths? *Pin 13?

--- 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.

That is my question. Why do you have output A and output B (pin 11
and 14
)
grounded?

Also, pin 13 is VC in for the transistor collectors. Why do you have
this connected as an output?- Hide quoted text -

- Show quoted text -

Yes the sawtooth is on pin 13. Pin 13 is being used as an output and
pins 11 and 14 are grounded because the chip is being used in single-
ended supply mode (see
http://www.datasheetcatalog.org/data...G3525AN.pdfp.6
for an example of this configuration). I can see why you find that
strange--I did too!

I'd avoid the funky setup you have. In my opinion I'd connect pin 13 and 15
together and use either output A or B.

I'm not sure what Q4 is doing, I've never seen it used this way, but you
must know more than me since you designed this elaborte circuit.

Keep us posted at what you do to resolve the problem.- Hide quoted text -

- Show quoted text -

It's not my design. I am trying to repair a commercial unit. I will
keep you posted.

On Jul 4, 11:13 am, alphamnemonic wrote:
On Jul 3, 6:09 pm, Steve wrote:



alphamnemonic wrote :

On Jul 2, 6:20 pm, Steve wrote:
wrote in news:16ea6110-be19-4a21-aecc-
:

On Jul 2, 3:35 pm, alphamnemonic wrote:
Hi Everybody

This chip normally puts out square pulses. In the power supply I
am working on (http://www.laserfaq.org/sam/150rcsch.pdf) it is
putting out a sawtooth wave. I am testing it in 'standby mode', in
which Q4 is off and R33 is in control of the duty cycle. Replacing
the IC1 has no effect. Does anyone have any ideas?

Where are you seeing sawtooths? Pin 13?

--- 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.

That is my question. Why do you have output A and output B (pin 11
and 14
)
grounded?

Also, pin 13 is VC in for the transistor collectors. Why do you have
this connected as an output?- Hide quoted text -

- Show quoted text -

Yes the sawtooth is on pin 13. Pin 13 is being used as an output and
pins 11 and 14 are grounded because the chip is being used in single-
ended supply mode (see
http://www.datasheetcatalog.org/data...G3525AN.pdfp.6
for an example of this configuration). I can see why you find that
strange--I did too!

I'd avoid the funky setup you have. In my opinion I'd connect pin 13 and 15
together and use either output A or B.

I'm not sure what Q4 is doing, I've never seen it used this way, but you
must know more than me since you designed this elaborte circuit.

Keep us posted at what you do to resolve the problem.- Hide quoted text -

- Show quoted text -

It's not my design. I am trying to repair a commercial unit. I will
keep you posted.

First, I've never scoped pin 13 so don't know for sure what should be
there.

But, my guess is that one of the 3 transistors is not behaving
properly.and you're
seeing one of the caps charging.

--- 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.

Steve wrote in
6:

alphamnemonic wrote in
news:ba29f199-331f-48c1-ab96-28c3a81d42d8
@i18g2000prn.googlegroups.com:

On Jul 2, 6:20*pm, Steve wrote:
wrote in news:16ea6110-be19-4a21-aecc-
:





On Jul 2, 3:35 pm, alphamnemonic wrote:
Hi Everybody

This chip normally puts out square pulses. In the power supply I
am working on (http://www.laserfaq.org/sam/150rcsch.pdf) it is
putting out a sawtooth wave. I am testing it in 'standby mode',
in which Q4 is off and R33 is in control of the duty cycle.
Replacing the IC1 has no effect. Does anyone have any ideas?

Where are you seeing sawtooths? *Pin 13?

--- 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.

That is my question. Why do you have output A and output B (pin 11
and 14
)
grounded?

Also, pin 13 is VC in for the transistor collectors. Why do you have
this connected as an output?- Hide quoted text -

- Show quoted text -

Yes the sawtooth is on pin 13. Pin 13 is being used as an output and
pins 11 and 14 are grounded because the chip is being used in single-
ended supply mode (see
http://www.datasheetcatalog.org/data...a/SG3525AN.pdf p.6
for an example of this configuration). I can see why you find that
strange--I did too!


I'd avoid the funky setup you have. In my opinion I'd connect pin 13
and 15 together and use either output A or B.

I'm not sure what Q4 is doing, I've never seen it used this way, but
you must know more than me since you designed this elaborte circuit.


Keep us posted at what you do to resolve the problem.


I have been looking at the circuit and the datasheet.

I'm willing to bet the schematic is drawn wrong. It doesn't make any
sense to have pin 13 driving the base of a transistor.

On Jul 7, 6:09Â*pm, Steve wrote:
Steve wrote . 136:

alphamnemonic wrote in
news:ba29f199-331f-48c1-ab96-28c3a81d42d8

@i18g2000prn.googlegroups.com:







On Jul 2, 6:20�pm, Steve wrote:
wrote in news:16ea6110-be19-4a21-aecc-
:

On Jul 2, 3:35 pm, alphamnemonic wrote:
Hi Everybody

This chip normally puts out square pulses. In the power supply I
am working on (http://www.laserfaq.org/sam/150rcsch.pdf) it is
putting out a sawtooth wave. I am testing it in 'standby mode',
in which Q4 is off and R33 is in control of the duty cycle.
Replacing the IC1 has no effect. Does anyone have any ideas?

Where are you seeing sawtooths? �Pin 13?

--- 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.

That is my question. Why do you have output A and output B (pin 11
and 14
)
grounded?

Also, pin 13 is VC in for the transistor collectors. Why do you have
this connected as an output?- Hide quoted text -

- Show quoted text -

Yes the sawtooth is on pin 13. Pin 13 is being used as an output and
pins 11 and 14 are grounded because the chip is being used in single-
ended supply mode (see
http://www.datasheetcatalog.org/data...G3525AN.pdfp.6
for an example of this configuration). I can see why you find that
strange--I did too!

I'd avoid the funky setup you have. In my opinion I'd connect pin 13
and 15 together and use either output A or B.

I'm not sure what Q4 is doing, I've never seen it used this way, but
you must know more than me since you designed this elaborte circuit.

Keep us posted at what you do to resolve the problem.

I have been looking at the circuit and the datasheet.

I'm willing to bet the schematic is drawn wrong. It doesn't make any
sense to have pin 13 driving the base of a transistor.- Hide quoted text -

- Show quoted text -

The schematic is drawn correctly. This mode of operation is described
on p.6 of the datasheet (link is given in my post from July 3). I
removed the board and re-soldered R1 and R2, and the supply is now
working properly again. A rather boring fix, but if it works long term
I won't complain... If anyone else is having trouble with this supply,
I can send you waveforms captured with FlukeView from the working
unit. Thanks for the suggestions everyone.

alphamnemonic wrote in
:

On Jul 7, 6:09Â*pm, Steve wrote:
Steve wrote
innews:Xns9AD0CDEF8F97Fnobodynobodycom@21
6.196.97.136:

alphamnemonic wrote in
news:ba29f199-331f-48c1-ab96-28c3a81d42d8

@i18g2000prn.googlegroups.com:







On Jul 2, 6:20�pm, Steve wrote:
wrote in news:16ea6110-be19-4a21-aecc-
:

On Jul 2, 3:35 pm, alphamnemonic wrote:
Hi Everybody

This chip normally puts out square pulses. In the power supply
I am working on (http://www.laserfaq.org/sam/150rcsch.pdf) it
is putting out a sawtooth wave. I am testing it in 'standby
mode', in which Q4 is off and R33 is in control of the duty
cycle. Replacing the IC1 has no effect. Does anyone have any
ideas?

Where are you seeing sawtooths? �Pin 13?

--- sam | Sci.Electronics.Repair FAQ:http://www.repairfaq.org/
�Repair | Main Table of Contents:http://www.repairfaq.org/R
EPAIR/
+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.

That is my question. Why do you have output A and output B (pin
11 and 14
)
grounded?

Also, pin 13 is VC in for the transistor collectors. Why do you
have this connected as an output?- Hide quoted text -

- Show quoted text -

Yes the sawtooth is on pin 13. Pin 13 is being used as an output
and pins 11 and 14 are grounded because the chip is being used in
single- ended supply mode (see
http://www.datasheetcatalog.org/data...G3525AN.pdfp.6
for an example of this configuration). I can see why you find that
strange--I did too!

I'd avoid the funky setup you have. In my opinion I'd connect pin
13 and 15 together and use either output A or B.

I'm not sure what Q4 is doing, I've never seen it used this way,
but you must know more than me since you designed this elaborte
circuit.

Keep us posted at what you do to resolve the problem.

I have been looking at the circuit and the datasheet.

I'm willing to bet the schematic is drawn wrong. It doesn't make any
sense to have pin 13 driving the base of a transistor.- Hide quoted
text
-

- Show quoted text -

The schematic is drawn correctly. This mode of operation is described
on p.6 of the datasheet (link is given in my post from July 3). I
removed the board and re-soldered R1 and R2, and the supply is now
working properly again. A rather boring fix, but if it works long term
I won't complain... If anyone else is having trouble with this supply,
I can send you waveforms captured with FlukeView from the working
unit. Thanks for the suggestions everyone.


I'd like to see them. Do you have them in a format you can easily email?

On Jul 14, 4:50Â*pm, Steve wrote:
alphamnemonic wrote :





On Jul 7, 6:09Â*pm, Steve wrote:
Steve wrote
innews:Xns9AD0CDEF8F97Fnobodynobodycom@21
6.196.97.136:

alphamnemonic wrote in
news:ba29f199-331f-48c1-ab96-28c3a81d42d8

@i18g2000prn.googlegroups.com:

On Jul 2, 6:20�pm, Steve wrote:
wrote in news:16ea6110-be19-4a21-aecc-
:

On Jul 2, 3:35 pm, alphamnemonic wrote:
Hi Everybody

This chip normally puts out square pulses. In the power supply
I am working on (http://www.laserfaq.org/sam/150rcsch.pdf) it
is putting out a sawtooth wave. I am testing it in 'standby
mode', in which Q4 is off and R33 is in control of the duty
cycle. Replacing the IC1 has no effect. Does anyone have any
ideas?

Where are you seeing sawtooths? �Pin 13?

--- sam | Sci.Electronics.Repair FAQ:http://www.repairfaq.org/
�Repair | Main Table of Contents:http://www.repairfaq.org/R
EPAIR/
+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
Â*in the
FAQs.

That is my question. Why do you have output A and output B (pin
11 and 14
)
grounded?

Also, pin 13 is VC in for the transistor collectors. Why do you
have this connected as an output?- Hide quoted text -

- Show quoted text -

Yes the sawtooth is on pin 13. Pin 13 is being used as an output
and pins 11 and 14 are grounded because the chip is being used in
single- ended supply mode (see
http://www.datasheetcatalog.org/data...G3525AN.pdfp.6
for an example of this configuration). I can see why you find that
strange--I did too!

I'd avoid the funky setup you have. In my opinion I'd connect pin
13 and 15 together and use either output A or B.

I'm not sure what Q4 is doing, I've never seen it used this way,
but you must know more than me since you designed this elaborte
circuit.

Keep us posted at what you do to resolve the problem.

I have been looking at the circuit and the datasheet.

I'm willing to bet the schematic is drawn wrong. It doesn't make any
sense to have pin 13 driving the base of a transistor.- Hide quoted
text
-

- Show quoted text -

The schematic is drawn correctly. This mode of operation is described
on p.6 of the datasheet (link is given in my post from July 3). I
removed the board and re-soldered R1 and R2, and the supply is now
working properly again. A rather boring fix, but if it works long term
I won't complain... If anyone else is having trouble with this supply,
I can send you waveforms captured with FlukeView from the working
unit. Thanks for the suggestions everyone.

I'd like to see them. Do you have them in a format you can easily email?- Hide quoted text -

- Show quoted text -

Yes: .rtf

alphamnemonic wrote in
:

On Jul 14, 4:50Â*pm, Steve wrote:
alphamnemonic wrote
innews:e7294911-213d-4734-b0cd-
:





On Jul 7, 6:09Â*pm, Steve wrote:
Steve wrote
innews:Xns9AD0CDEF8F97Fnobodynobodycom@21
6.196.97.136:

alphamnemonic wrote in
news:ba29f199-331f-48c1-ab96-28c3a81d42d8

@i18g2000prn.googlegroups.com:

On Jul 2, 6:20�pm, Steve wrote:
wrote in news:16ea6110-be19-4a21-aecc-
:

On Jul 2, 3:35 pm, alphamnemonic
wrote:
Hi Everybody

This chip normally puts out square pulses. In the power
supply I am working on
(http://www.laserfaq.org/sam/150rcsch.pdf) it
is putting out a sawtooth wave. I am testing it in 'standby
mode', in which Q4 is off and R33 is in control of the duty
cycle. Replacing the IC1 has no effect. Does anyone have
any ideas?

Where are you seeing sawtooths? �Pin 13?

--- sam | Sci.Electronics.Repair
FAQ:http://www.repairfaq.org/ �Repair | Main Table of
Contents:http://www.repairfaq.or
g/R
EPAIR/
+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 F
orm
Â*in the
FAQs.

That is my question. Why do you have output A and output B
(pin 11 and 14
)
grounded?

Also, pin 13 is VC in for the transistor collectors. Why do
you have this connected as an output?- Hide quoted text -

- Show quoted text -

Yes the sawtooth is on pin 13. Pin 13 is being used as an
output and pins 11 and 14 are grounded because the chip is
being used in single- ended supply mode (see

http://www.datasheetcatalog.org/data.../SG3525AN.pdfp.
6
for an example of this configuration). I can see why you find
that strange--I did too!

I'd avoid the funky setup you have. In my opinion I'd connect
pin 13 and 15 together and use either output A or B.

I'm not sure what Q4 is doing, I've never seen it used this way,
but you must know more than me since you designed this elaborte
circuit.

Keep us posted at what you do to resolve the problem.

I have been looking at the circuit and the datasheet.

I'm willing to bet the schematic is drawn wrong. It doesn't make
any sense to have pin 13 driving the base of a transistor.- Hide
quoted text
-

- Show quoted text -

The schematic is drawn correctly. This mode of operation is
described on p.6 of the datasheet (link is given in my post from
July 3). I removed the board and re-soldered R1 and R2, and the
supply is now working properly again. A rather boring fix, but if
it works long term I won't complain... If anyone else is having
trouble with this supply, I can send you waveforms captured with
FlukeView from the working unit. Thanks for the suggestions
everyone.

I'd like to see them. Do you have them in a format you can easily
email?-
Hide quoted text -

- Show quoted text -

Yes: .rtf

I phrased that incorrectly.

I meant can you post them on here for downloading or on a site?


Thanks

On Jul 16, 6:12Â*pm, Steve wrote:
alphamnemonic wrote :





On Jul 14, 4:50Â*pm, Steve wrote:
alphamnemonic wrote
innews:e7294911-213d-4734-b0cd-
:

On Jul 7, 6:09Â*pm, Steve wrote:
Steve wrote
innews:Xns9AD0CDEF8F97Fnobodynobodycom@21
6.196.97.136:

alphamnemonic wrote in
news:ba29f199-331f-48c1-ab96-28c3a81d42d8

@i18g2000prn.googlegroups.com:

On Jul 2, 6:20�pm, Steve wrote:
wrote in news:16ea6110-be19-4a21-aecc-
:

On Jul 2, 3:35 pm, alphamnemonic
wrote:
Hi Everybody

This chip normally puts out square pulses. In the power
supply I am working on
(http://www.laserfaq.org/sam/150rcsch.pdf) it
is putting out a sawtooth wave. I am testing it in 'standby
mode', in which Q4 is off and R33 is in control of the duty
cycle. Replacing the IC1 has no effect. Does anyone have
any ideas?

Where are you seeing sawtooths? �Pin 13?

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That is my question. Why do you have output A and output B
(pin 11 and 14
)
grounded?

Also, pin 13 is VC in for the transistor collectors. Why do
you have this connected as an output?- Hide quoted text -

- Show quoted text -

Yes the sawtooth is on pin 13. Pin 13 is being used as an
output and pins 11 and 14 are grounded because the chip is
being used in single- ended supply mode (see

http://www.datasheetcatalog.org/data.../SG3525AN.pdfp.





6
for an example of this configuration). I can see why you find
that strange--I did too!

I'd avoid the funky setup you have. In my opinion I'd connect
pin 13 and 15 together and use either output A or B.

I'm not sure what Q4 is doing, I've never seen it used this way,
but you must know more than me since you designed this elaborte
circuit.

Keep us posted at what you do to resolve the problem.

I have been looking at the circuit and the datasheet.

I'm willing to bet the schematic is drawn wrong. It doesn't make
any sense to have pin 13 driving the base of a transistor.- Hide
quoted text
-

- Show quoted text -

The schematic is drawn correctly. This mode of operation is
described on p.6 of the datasheet (link is given in my post from
July 3). I removed the board and re-soldered R1 and R2, and the
supply is now working properly again. A rather boring fix, but if
it works long term I won't complain... If anyone else is having
trouble with this supply, I can send you waveforms captured with
FlukeView from the working unit. Thanks for the suggestions
everyone.

I'd like to see them. Do you have them in a format you can easily
email?-
Â*Hide quoted text -

- Show quoted text -

Yes: .rtf

I phrased that incorrectly.

I meant can you post them on here for downloading or on a site?

Thanks- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

I don't have a website, but I will post them here if you tell me how.

alphamnemonic wrote:

I don't have a website, but I will post them here if you tell me how.


This isn't a binary newsgroup, and you can't post pictures through
Google Groups.

Sign up for a free photo hosting service and post the link to the
pictures.


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Sporadic E is the Earth's aluminum foil beanie for the 'global warming'
sheep.

On Jul 17, 11:08*am, "Michael A. Terrell"
wrote:
alphamnemonic wrote:

I don't have a website, but I will post them here if you tell me how.

* *This isn't a binary newsgroup, and you can't post pictures through
Google Groups.

* *Sign up for a free photo hosting service and post the link to the
pictures.

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If you have broadband, your ISP may have a NNTP news server included in
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Sporadic E is the Earth's aluminum foil beanie for the 'global warming'
sheep.

The pics are up at http://sites.google.com/site/scienti...tronicsrepair/

alphamnemonic wrote in
:

On Jul 17, 11:08*am, "Michael A. Terrell"
wrote:
alphamnemonic wrote:

I don't have a website, but I will post them here if you tell me
how.

* *This isn't a binary newsgroup, and you can't post pictures through
Google Groups.

* *Sign up for a free photo hosting service and post the link to the
pictures.

--http://improve-usenet.org/index.html

If you have broadband, your ISP may have a NNTP news server included
in your account:http://www.usenettools.net/ISP.htm

Sporadic E is the Earth's aluminum foil beanie for the 'global
warming' sheep.

The pics are up at
http://sites.google.com/site/scienti...tronicsrepair/

Those are interesting waveforms.

Nothing I would have expected if I was working on this or I didn't have a
known working unit for comparision.