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PWM Control IC Problem (SG3525)
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? |
PWM Control IC Problem (SG3525)
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. |
PWM Control IC Problem (SG3525)
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! |
PWM Control IC Problem (SG3525)
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. |
PWM Control IC Problem (SG3525)
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. |
PWM Control IC Problem (SG3525)
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. |
PWM Control IC Problem (SG3525)
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. |
PWM Control IC Problem (SG3525)
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. |
PWM Control IC Problem (SG3525)
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? |
PWM Control IC Problem (SG3525)
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 |
PWM Control IC Problem (SG3525)
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 |
PWM Control IC Problem (SG3525)
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. |
PWM Control IC Problem (SG3525)
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. |
PWM Control IC Problem (SG3525)
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/ |
PWM Control IC Problem (SG3525)
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. |
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