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?

--- 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?-
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.