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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Chicken or the egg ?
I know this is just a pc ps but I'd like to understand what is going on, or
not going on, even if not repaird. There are 3 HF transformers and an opto-isolator bridging the HV and LV sides. The startup oscillator, on the HV side, is a KA1H0165R whose o/p crosses the divide to give a Vcc of 12V on the main SMPS controller a KA3511DS, both datasheets downloaded. This controller o/p should then cross the divide to drive the HV side main oscillator to drive the main transformer back to the LV side supply rails. The SMPS "flag" output pin goes high meaning no-function and no o/p pulses for either push-pull output of this KA3511. As the KA3511 monitors over-voltage, and more to this point, under-voltage of the supply rails , how should it ever get started if it never outputs any main drive pulses, so no main supply rails. If i find time today I will run the KA3511 from 12V bench supply and see what happens . -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#2
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Chicken or the egg ?
N Cook wrote: There are 3 HF transformers More likely one transformer and 2 chokes, unless you have a specific reason to say otherwise. Graham |
#3
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Chicken or the egg ?
Eeyore wrote in message
... N Cook wrote: There are 3 HF transformers More likely one transformer and 2 chokes, unless you have a specific reason to say otherwise. Graham Why would chokes bridge the "no man's land" isolation strip between HV and LV areas ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#4
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Chicken or the egg ?
"N Cook" writes:
Eeyore wrote in message ... N Cook wrote: There are 3 HF transformers More likely one transformer and 2 chokes, unless you have a specific reason to say otherwise. Why would chokes bridge the "no man's land" isolation strip between HV and LV areas ? No, probably transformers instead of opto-isolators (on the feedback and drive). Personally, I wouldn't even attempt to do any serious troubleshooting on a supply of this type unless there was no inexpensive replacement. I would check the obvious - ESR of e-caps, open high value startup resistors, and such. But beyond that, these tend to be infinite frustration sources. --- 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. |
#5
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Chicken or the egg ?
Sam Goldwasser wrote in message
... "N Cook" writes: Eeyore wrote in message ... N Cook wrote: There are 3 HF transformers More likely one transformer and 2 chokes, unless you have a specific reason to say otherwise. Why would chokes bridge the "no man's land" isolation strip between HV and LV areas ? No, probably transformers instead of opto-isolators (on the feedback and drive). Personally, I wouldn't even attempt to do any serious troubleshooting on a supply of this type unless there was no inexpensive replacement. I would check the obvious - ESR of e-caps, open high value startup resistors, and such. But beyond that, these tend to be infinite frustration sources. --- 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. I don't mind challenges unless someone wants a turnaround repair, which this is not. Its just practise for some future dedicated complex supply that has no generic replacement. I can see the one large and two small HF transformers tied up with the above process but I wonder what the 4 pin opto device is for, perhaps an overall on/off killer: when the controller flag is high it locks out the main HV oscillator from making any blips. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#6
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Chicken or the egg ?
On Thu, 4 Oct 2007 09:32:41 +0100, "N Cook" put
finger to keyboard and composed: I know this is just a pc ps but I'd like to understand what is going on, or not going on, even if not repaird. There are 3 HF transformers and an opto-isolator bridging the HV and LV sides. The startup oscillator, on the HV side, is a KA1H0165R whose o/p crosses the divide to give a Vcc of 12V on the main SMPS controller a KA3511DS, both datasheets downloaded. This controller o/p should then cross the divide to drive the HV side main oscillator to drive the main transformer back to the LV side supply rails. The SMPS "flag" output pin goes high meaning no-function and no o/p pulses for either push-pull output of this KA3511. As the KA3511 monitors over-voltage, and more to this point, under-voltage of the supply rails , how should it ever get started if it never outputs any main drive pulses, so no main supply rails. If i find time today I will run the KA3511 from 12V bench supply and see what happens . If it's a typical ATX PSU, then one transformer is part of the +5VSB supply, a second drives the oscillator/chopper, and the third supplies the secondaries. The optoisolator may provide voltage feedback for the +5VSB rail, or it may be part of a protection circuit that shuts down the oscillator. See http://www.pavouk.org/hw/en_atxps.html. Otherwise, if you have an AT PSU, then AFAIK the PWM controller on the secondary side gets its supply rail from the very first "kick" of the main oscillator and then "bootstraps" itself into regulation. - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#7
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Chicken or the egg ?
Franc Zabkar wrote in message
... On Thu, 4 Oct 2007 09:32:41 +0100, "N Cook" put finger to keyboard and composed: I know this is just a pc ps but I'd like to understand what is going on, or not going on, even if not repaird. There are 3 HF transformers and an opto-isolator bridging the HV and LV sides. The startup oscillator, on the HV side, is a KA1H0165R whose o/p crosses the divide to give a Vcc of 12V on the main SMPS controller a KA3511DS, both datasheets downloaded. This controller o/p should then cross the divide to drive the HV side main oscillator to drive the main transformer back to the LV side supply rails. The SMPS "flag" output pin goes high meaning no-function and no o/p pulses for either push-pull output of this KA3511. As the KA3511 monitors over-voltage, and more to this point, under-voltage of the supply rails , how should it ever get started if it never outputs any main drive pulses, so no main supply rails. If i find time today I will run the KA3511 from 12V bench supply and see what happens . If it's a typical ATX PSU, then one transformer is part of the +5VSB supply, a second drives the oscillator/chopper, and the third supplies the secondaries. The optoisolator may provide voltage feedback for the +5VSB rail, or it may be part of a protection circuit that shuts down the oscillator. See http://www.pavouk.org/hw/en_atxps.html. Otherwise, if you have an AT PSU, then AFAIK the PWM controller on the secondary side gets its supply rail from the very first "kick" of the main oscillator and then "bootstraps" itself into regulation. - Franc Zabkar -- Please remove one 'i' from my address when replying by email. Didn't get around to powering from 12V dc but did trace a bit of the tracks. The opto would seem to link, DC fashion, from the 3.3V rail back to the feedback pin of the low power startup IC to shut that one down. This IC, with the reservoir caps, will keep the main smps IC running for 10 seconds after removing the mains supply (in the present unfunctional as a ps state) -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#8
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Chicken or the egg ?
"N Cook" writes:
Sam Goldwasser wrote in message ... "N Cook" writes: Eeyore wrote in message ... N Cook wrote: There are 3 HF transformers More likely one transformer and 2 chokes, unless you have a specific reason to say otherwise. Why would chokes bridge the "no man's land" isolation strip between HV and LV areas ? No, probably transformers instead of opto-isolators (on the feedback and drive). Personally, I wouldn't even attempt to do any serious troubleshooting on a supply of this type unless there was no inexpensive replacement. I would check the obvious - ESR of e-caps, open high value startup resistors, and such. But beyond that, these tend to be infinite frustration sources. --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ I don't mind challenges unless someone wants a turnaround repair, which this is not. Its just practise for some future dedicated complex supply that has no generic replacement. I can see the one large and two small HF transformers tied up with the above process but I wonder what the 4 pin opto device is for, perhaps an overall on/off killer: when the controller flag is high it locks out the main HV oscillator from making any blips. Could be, since the transformers can't provide DC coupling. The problem is that with no schematic or service manual, there can be so many dead ends and confusion that the experience IMO may not transfer to other areas. It's not clear that the knowledge gained is worth the hair lost. --- 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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