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Finding A Power Supply Schematic
[This followup was posted to sci.electronics.repair and a copy was sent to the cited author.]
I am repairing an LCD monitor that has the very common turn on problems. This is an I-INC IF281D unit with model number showing as HSD1040. I am in the process of replacing all the capacitors on the PhiHong power supply board (model PSM217-404-H-R) and have noticed that one transistor looks like it got excessively hot. I would like to replace that transistor but have to first ID the part number. To this end I have two questions... Does anyone know where it may be possible to get a schematic for the PSM217-404-H-R power supply board? The overheated transistor is an SMT device with a code DFRG marked on top. Any idea as to what that part number may be? -- Michael Karas Carousel Design Solutions http://www.carousel-design.com |
Finding A Power Supply Schematic
Michael Karas wrote in message
... [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] I am repairing an LCD monitor that has the very common turn on problems. This is an I-INC IF281D unit with model number showing as HSD1040. I am in the process of replacing all the capacitors on the PhiHong power supply board (model PSM217-404-H-R) and have noticed that one transistor looks like it got excessively hot. I would like to replace that transistor but have to first ID the part number. To this end I have two questions... Does anyone know where it may be possible to get a schematic for the PSM217-404-H-R power supply board? The overheated transistor is an SMT device with a code DFRG marked on top. Any idea as to what that part number may be? -- Michael Karas Carousel Design Solutions http://www.carousel-design.com Is there a "bleed-through" route for start-up? |
Finding A Power Supply Schematic
[This followup was posted to sci.electronics.repair and a copy was sent
to the cited author.] In article , says... Is there a "bleed-through" route for start-up? I do not really know what you are asking about here. This unit came to me as a freeby already taken apart and the report that "It does not turn on". So I just dived in with the power supply capacitor replacement since that has worked many many times on other monitors (~ 15 so far). I noticed that the particular transistor in question has discolored leads and solder joints and the PC board has turned to a darker color than normal. -- Michael Karas Carousel Design Solutions http://www.carousel-design.com |
Finding A Power Supply Schematic
Michael Karas wrote in message
... [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] In article , says... Is there a "bleed-through" route for start-up? I do not really know what you are asking about here. This unit came to me as a freeby already taken apart and the report that "It does not turn on". So I just dived in with the power supply capacitor replacement since that has worked many many times on other monitors (~ 15 so far). I noticed that the particular transistor in question has discolored leads and solder joints and the PC board has turned to a darker color than normal. -- Michael Karas Carousel Design Solutions http://www.carousel-design.com You need to identify the supervisor IC and get its pinout hopefully. |
Finding A Power Supply Schematic
Michael Karas schrieb:
[This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] In article , says... Is there a "bleed-through" route for start-up? I do not really know what you are asking about here. ... This http://www.bilder-hochladen.net/files/big/12b4-a6-6c52.jpg is a typical schematic for a SMPS. The supply voltage for the controlling IC is provided via R1 for the first moment - I think this is N_Cook's "bleed-through" route. When the circuit is working the supply voltage is generated by W3/D1/C6. If R1 is open and/or C6 has a short the SMPS won't start. HTH Reinhard |
Finding A Power Supply Schematic
"Michael Karas" wrote in message ... [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] In article , says... Is there a "bleed-through" route for start-up? I do not really know what you are asking about here. Its common practice for the SMPSU control chip Vcc to come from an extra winding on the chopper transformer. Before the PSU starts up - there has to be some source of Vcc to get it kick started. Very often there's a high resistance resistor (or 2 in series) from the +ve of the mains bridge to provide the initial start up supply for the control chip - these resistors are very prone to going high/OC. |
Finding A Power Supply Schematic
On Fri, 24 May 2013 06:08:53 -0700, Michael Karas
wrote: [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] I am repairing an LCD monitor that has the very common turn on problems. This is an I-INC IF281D unit with model number showing as HSD1040. I am in the process of replacing all the capacitors on the PhiHong power supply board (model PSM217-404-H-R) and have noticed that one transistor looks like it got excessively hot. I would like to replace that transistor but have to first ID the part number. To this end I have two questions... Does anyone know where it may be possible to get a schematic for the PSM217-404-H-R power supply board? The overheated transistor is an SMT device with a code DFRG marked on top. Any idea as to what that part number may be? Google 'marking code DFRG' and see if anything makes sense. Also, SMT is a very generic term. If we knew the specific package, it would help us help you. Another resource, especially whre power supplies for LCD monitors are concerned is www,badcaps.net/forum. Pictures help. PlainBill |
Finding A Power Supply Schematic
"Ian Field" wrote in message ... "Michael Karas" wrote in message ... [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] In article , says... Is there a "bleed-through" route for start-up? I do not really know what you are asking about here. Its common practice for the SMPSU control chip Vcc to come from an extra winding on the chopper transformer. Before the PSU starts up - there has to be some source of Vcc to get it kick started. Very often there's a high resistance resistor (or 2 in series) from the +ve of the mains bridge to provide the initial start up supply for the control chip - these resistors are very prone to going high/OC. +1 And the cap in the C6 position on Reinhard's schematic is the one component that I change more of on every design of switcher that I work on, than any other component for no or intermittent start up. As the startup resistor is such a high value, that cap has to be in near-perfect condition to buffer that startup supply down to a low impedance for the control chip, until the supply gets going, and the low impedance maintenance supply takes over. An ESR meter is your friend here ... Arfa |
Finding A Power Supply Schematic
"Arfa Daily" wrote in message ... "Ian Field" wrote in message ... "Michael Karas" wrote in message ... [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] In article , says... Is there a "bleed-through" route for start-up? I do not really know what you are asking about here. Its common practice for the SMPSU control chip Vcc to come from an extra winding on the chopper transformer. Before the PSU starts up - there has to be some source of Vcc to get it kick started. Very often there's a high resistance resistor (or 2 in series) from the +ve of the mains bridge to provide the initial start up supply for the control chip - these resistors are very prone to going high/OC. +1 And the cap in the C6 position on Reinhard's schematic is the one component that I change more of on every design of switcher that I work on, than any other component for no or intermittent start up. As the startup resistor is such a high value, that cap has to be in near-perfect condition to buffer that startup supply down to a low impedance for the control chip, until the supply gets going, and the low impedance maintenance supply takes over. An ESR meter is your friend here ... I don't have that particular schematic, but in general terms such capacitors are usually quite small ( 1 - 47uF) such values are easy to get hold of in multilayer ceramic chip capacitors - and the electrolyte will never dry out. |
Finding A Power Supply Schematic
Ian Field schrieb:
"Arfa Daily" wrote in message [...] And the cap in the C6 position on Reinhard's schematic ... I don't have that particular schematic, ... Hmm, can't you see my posting as of May 24 with the link to that schematic? Wondering Reinhard |
Finding A Power Supply Schematic
Ian Field wrote in message
... "Arfa Daily" wrote in message ... "Ian Field" wrote in message ... "Michael Karas" wrote in message ... [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] In article , says... Is there a "bleed-through" route for start-up? I do not really know what you are asking about here. Its common practice for the SMPSU control chip Vcc to come from an extra winding on the chopper transformer. Before the PSU starts up - there has to be some source of Vcc to get it kick started. Very often there's a high resistance resistor (or 2 in series) from the +ve of the mains bridge to provide the initial start up supply for the control chip - these resistors are very prone to going high/OC. +1 And the cap in the C6 position on Reinhard's schematic is the one component that I change more of on every design of switcher that I work on, than any other component for no or intermittent start up. As the startup resistor is such a high value, that cap has to be in near-perfect condition to buffer that startup supply down to a low impedance for the control chip, until the supply gets going, and the low impedance maintenance supply takes over. An ESR meter is your friend here ... I don't have that particular schematic, but in general terms such capacitors are usually quite small ( 1 - 47uF) such values are easy to get hold of in multilayer ceramic chip capacitors - and the electrolyte will never dry out. But MLCCs then have their own problems, excess heat from PbF fixing, lead to cracks and then metal migration into the cracks due to the tiny geometries http://web.archive.org/web/200805120.../news/rfa_feat ure_07b.asp I don't know the relative frequency of each failure process though |
Finding A Power Supply Schematic
"Reinhard Zwirner" wrote in message ... Ian Field schrieb: "Arfa Daily" wrote in message [...] And the cap in the C6 position on Reinhard's schematic ... I don't have that particular schematic, ... Hmm, can't you see my posting as of May 24 with the link to that schematic? Wondering Reinhard The only link I can see on that post is carousel-design. Maybe you could repost? |
Finding A Power Supply Schematic
"N_Cook" wrote in message ... Ian Field wrote in message ... "Arfa Daily" wrote in message ... "Ian Field" wrote in message ... "Michael Karas" wrote in message ... [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] In article , says... Is there a "bleed-through" route for start-up? I do not really know what you are asking about here. Its common practice for the SMPSU control chip Vcc to come from an extra winding on the chopper transformer. Before the PSU starts up - there has to be some source of Vcc to get it kick started. Very often there's a high resistance resistor (or 2 in series) from the +ve of the mains bridge to provide the initial start up supply for the control chip - these resistors are very prone to going high/OC. +1 And the cap in the C6 position on Reinhard's schematic is the one component that I change more of on every design of switcher that I work on, than any other component for no or intermittent start up. As the startup resistor is such a high value, that cap has to be in near-perfect condition to buffer that startup supply down to a low impedance for the control chip, until the supply gets going, and the low impedance maintenance supply takes over. An ESR meter is your friend here ... I don't have that particular schematic, but in general terms such capacitors are usually quite small ( 1 - 47uF) such values are easy to get hold of in multilayer ceramic chip capacitors - and the electrolyte will never dry out. But MLCCs then have their own problems, excess heat from PbF fixing, lead to cracks and then metal migration into the cracks due to the tiny geometries Plenty of manufacturers make leaded & resin dipped versions - I've seen values offered as high as 180uF. So far I've always had sufficient parts from salvage, most often I add one to the print side to take the edge off the ripple current after replacing the electrolytic. Frequently the error voltage sampling cap in a PSU is so small that a MLCC is ready to hand with the exact value so the electro is replaced altogether. |
Finding A Power Supply Schematic
"Michael Karas" wrote in message ... [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] In article , says... On Fri, 24 May 2013 06:08:53 -0700, Michael Karas wrote: [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] I am repairing an LCD monitor that has the very common turn on problems. This is an I-INC IF281D unit with model number showing as HSD1040. I am in the process of replacing all the capacitors on the PhiHong power supply board (model PSM217-404-H-R) and have noticed that one transistor looks like it got excessively hot. I would like to replace that transistor but have to first ID the part number. To this end I have two questions... Does anyone know where it may be possible to get a schematic for the PSM217-404-H-R power supply board? The overheated transistor is an SMT device with a code DFRG marked on top. Any idea as to what that part number may be? Google 'marking code DFRG' and see if anything makes sense. Also, SMT is a very generic term. If we knew the specific package, it would help us help you. Another resource, especially whre power supplies for LCD monitors are concerned is www,badcaps.net/forum. Pictures help. PlainBill Here is a link to a picture of the transistor in question. https://docs.google.com/file/d/0BxTb...EMTlDaW8/edit? usp=sharing (Note link above may be split by a line break). The transistor package body is 2.5mm x 4mm. Lead spacing is 1.5mm. According to a document I checked here at the next link this package is a SOT-89 (also apparently referred to as a T0-243 or an SC-62). http://www.nxp.com/documents/outline.../sot089_po.pdf -- Michael Karas Carousel Design Solutions http://www.carousel-design.com I have seen much much worse than that. If it reads ok, I probably wouldn't bother too much about it ... Arfa |
Finding A Power Supply Schematic
Ian Field schrieb:
"Reinhard Zwirner" wrote in message [...] Hmm, can't you see my posting as of May 24 with the link to that schematic? The only link I can see on that post is carousel-design. ????? Maybe you could repost? Here is it: http://www.bilder-hochladen.net/files/big/12b4-a6-6c52.jpg Still wondering Reinhard |
Finding A Power Supply Schematic
On Sun, 26 May 2013 04:25:52 -0700, Michael Karas
wrote: [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] In article , says... On Fri, 24 May 2013 06:08:53 -0700, Michael Karas wrote: [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] I am repairing an LCD monitor that has the very common turn on problems. This is an I-INC IF281D unit with model number showing as HSD1040. I am in the process of replacing all the capacitors on the PhiHong power supply board (model PSM217-404-H-R) and have noticed that one transistor looks like it got excessively hot. I would like to replace that transistor but have to first ID the part number. To this end I have two questions... Does anyone know where it may be possible to get a schematic for the PSM217-404-H-R power supply board? The overheated transistor is an SMT device with a code DFRG marked on top. Any idea as to what that part number may be? Google 'marking code DFRG' and see if anything makes sense. Also, SMT is a very generic term. If we knew the specific package, it would help us help you. Another resource, especially whre power supplies for LCD monitors are concerned is www,badcaps.net/forum. Pictures help. PlainBill Here is a link to a picture of the transistor in question. https://docs.google.com/file/d/0BxTb...EMTlDaW8/edit? usp=sharing (Note link above may be split by a line break). The transistor package body is 2.5mm x 4mm. Lead spacing is 1.5mm. According to a document I checked here at the next link this package is a SOT-89 (also apparently referred to as a T0-243 or an SC-62). http://www.nxp.com/documents/outline.../sot089_po.pdf Excellent pictures, thanks. I believe the actual marking code is DF; the R indicates the gain and the G is a prouction lot or date code. My favorite source for arcane marking info: http://www.s-manuals.com Which leads to: http://www.s-manuals.com/smd/df And the datasheet: (watych out for line breaks) http://www.s-manuals.com/pdf/datashe...d1898_rohm.pdf IF you are in the USA, they are available from Digi-Key (ww.digikey.com) for $.53 each. (Choose USPS First Class Mail for lowest shipping cost.) As a general rule, I dissaprove of replacing parts because they 'look bad'. A few minutes making measurements with a DVM can give a wealth of information. PlainBill |
Finding A Power Supply Schematic
"Reinhard Zwirner" wrote in message ... Ian Field schrieb: "Reinhard Zwirner" wrote in message [...] Hmm, can't you see my posting as of May 24 with the link to that schematic? The only link I can see on that post is carousel-design. ????? Maybe you could repost? Here is it: http://www.bilder-hochladen.net/files/big/12b4-a6-6c52.jpg As advised; you should replace C6 - even if it isn't the culprit, it can cause all manner of nasty things to happen. I'd use a low ESR 105 deg-C part - and I'd put a MLCC on the print side to take the edge off its ripple current - but that's just my own preference. |
Finding A Power Supply Schematic
"Arfa Daily" wrote in message ... "Michael Karas" wrote in message ... [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] In article , says... On Fri, 24 May 2013 06:08:53 -0700, Michael Karas wrote: [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] I am repairing an LCD monitor that has the very common turn on problems. This is an I-INC IF281D unit with model number showing as HSD1040. I am in the process of replacing all the capacitors on the PhiHong power supply board (model PSM217-404-H-R) and have noticed that one transistor looks like it got excessively hot. I would like to replace that transistor but have to first ID the part number. To this end I have two questions... Does anyone know where it may be possible to get a schematic for the PSM217-404-H-R power supply board? The overheated transistor is an SMT device with a code DFRG marked on top. Any idea as to what that part number may be? Google 'marking code DFRG' and see if anything makes sense. Also, SMT is a very generic term. If we knew the specific package, it would help us help you. Another resource, especially whre power supplies for LCD monitors are concerned is www,badcaps.net/forum. Pictures help. PlainBill Here is a link to a picture of the transistor in question. https://docs.google.com/file/d/0BxTb...EMTlDaW8/edit? usp=sharing (Note link above may be split by a line break). The transistor package body is 2.5mm x 4mm. Lead spacing is 1.5mm. According to a document I checked here at the next link this package is a SOT-89 (also apparently referred to as a T0-243 or an SC-62). http://www.nxp.com/documents/outline.../sot089_po.pdf -- Michael Karas Carousel Design Solutions http://www.carousel-design.com I have seen much much worse than that. If it reads ok, I probably wouldn't bother too much about it ... A little old lady once called me out to a TCE B&W 'portable' (has a handle on top and is capable of 12V operation) one of those that the PCBs form a box around the back of the CRT. The little old lady said it had horizontal bars rolling up the screen, so she thumped it - then it went off! Of course the PSU PCB is along the top (upside down) the TO5 driver for the series pass TO3 was hot enough to melt its solder - when she thumped the set, the TO5 dropped in the bottom of the case. I had to go and get a replacement reservoir electrolytic to fix the original cause, but the transistor that melted its solder was perfectly fine and went back in. |
Finding A Power Supply Schematic
[This followup was posted to sci.electronics.repair and a copy was sent
to the cited author.] In article , says... Excellent pictures, thanks. I believe the actual marking code is DF; the R indicates the gain and the G is a prouction lot or date code. My favorite source for arcane marking info: http://www.s-manuals.com Which leads to: http://www.s-manuals.com/smd/df And the datasheet: (watych out for line breaks) http://www.s-manuals.com/pdf/datashe...C_2sd1768s%2C_ 2sd1863%2C_2sd1898_rohm.pdf IF you are in the USA, they are available from Digi-Key (ww.digikey.com) for $.53 each. (Choose USPS First Class Mail for lowest shipping cost.) As a general rule, I dissaprove of replacing parts because they 'look bad'. A few minutes making measurements with a DVM can give a wealth of information. PlainBill THanks for the info. I had also done some research on some other sites and find that there are multiple possibilities for this device marked with a DF. Sanyo NPN 2SD1623 Philips PNP BF621 Siemens PNP BNF21 Rohm NPN 2SD1898 ** ** The part that you located. I agree that this part should not be replaced if it is working. I had done some preliminary checking with the meter and it did not seem to respond with any forward biased junction readings and so I needed to get information as to whether this was some type of FET or a blown BJT transistor. When I get a power cord setup to be able fire up the board I will do some checking. I may also need to rig up a temoprary heatsink for a large diode bridge that gets screwed to part of the case that had to be removed to get at the board. Initial tests can probably avoid that if I just put small loads on the output rails for testing, -- Michael Karas Carousel Design Solutions http://www.carousel-design.com |
Finding A Power Supply Schematic
Ian Field schrieb:
"Reinhard Zwirner" wrote: Ian Field schrieb: "Reinhard Zwirner" wrote: Hmm, can't you see my posting as of May 24 with the link to that schematic? The only link I can see on that post is carousel-design. ????? Maybe you could repost? Here is it: http://www.bilder-hochladen.net/files/big/12b4-a6-6c52.jpg As advised; you should replace C6 ... It is Michael Karas who should try to repair his power supply by replacing the capacitor corresponding to C6 (or the resistor corresponding to R1) - not me! _I_ just tried to explain N_Cook's "bleed-through" route by a typical SMPS schematic as an example. Regards Reinhard |
Finding A Power Supply Schematic
wrote in message ... On Sun, 26 May 2013 04:25:52 -0700, Michael Karas wrote: [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] In article , says... On Fri, 24 May 2013 06:08:53 -0700, Michael Karas wrote: [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] I am repairing an LCD monitor that has the very common turn on problems. This is an I-INC IF281D unit with model number showing as HSD1040. I am in the process of replacing all the capacitors on the PhiHong power supply board (model PSM217-404-H-R) and have noticed that one transistor looks like it got excessively hot. I would like to replace that transistor but have to first ID the part number. To this end I have two questions... Does anyone know where it may be possible to get a schematic for the PSM217-404-H-R power supply board? The overheated transistor is an SMT device with a code DFRG marked on top. Any idea as to what that part number may be? Google 'marking code DFRG' and see if anything makes sense. Also, SMT is a very generic term. If we knew the specific package, it would help us help you. Another resource, especially whre power supplies for LCD monitors are concerned is www,badcaps.net/forum. Pictures help. PlainBill Here is a link to a picture of the transistor in question. https://docs.google.com/file/d/0BxTb...EMTlDaW8/edit? usp=sharing (Note link above may be split by a line break). The transistor package body is 2.5mm x 4mm. Lead spacing is 1.5mm. According to a document I checked here at the next link this package is a SOT-89 (also apparently referred to as a T0-243 or an SC-62). http://www.nxp.com/documents/outline.../sot089_po.pdf Excellent pictures, thanks. I believe the actual marking code is DF; the R indicates the gain and the G is a prouction lot or date code. My favorite source for arcane marking info: http://www.s-manuals.com Which leads to: http://www.s-manuals.com/smd/df And the datasheet: (watych out for line breaks) http://www.s-manuals.com/pdf/datashe...d1898_rohm.pdf IF you are in the USA, they are available from Digi-Key (ww.digikey.com) for $.53 each. (Choose USPS First Class Mail for lowest shipping cost.) As a general rule, I dissaprove of replacing parts because they 'look bad'. A few minutes making measurements with a DVM can give a wealth of information. PlainBill Based on years of experience at component level, +1 on that. Unless there is a very good reason, I've never been an advocate of 'shotgunning' for the hell of it ... Arfa |
Finding A Power Supply Schematic
When I get a power cord setup to be able fire up the board I will do some checking. I may also need to rig up a temoprary heatsink for a large diode bridge that gets screwed to part of the case that had to be removed to get at the board. Initial tests can probably avoid that if I just put small loads on the output rails for testing, -- Michael Karas Carousel Design Solutions http://www.carousel-design.com If available, I would strongly recommend the use of a proper bench isolating transformer when working on this. I'm sure that it is probably a case of grandmothers and egg-sucking as you seem to be saying the right things, but just in case ... Switchers are of course extremely dangerous on a 'raw' line supply. I usually have a variac connected as well. This can be either a help or a hindrance depending on design, but I always initially make the assumption that it is going to be a help, when I don't have a schematic. Although some supplies have UVLO on the control IC, so won't start with a reduced input voltage, it does at least allow you to carry out checks on - for instance - the startup supply, in a safe manner, and without the risk of a Disney-esque fireworks display, when your meter or 'scope probe slips, which it always will sooner or later, depending on how urgent the job is, and how rare the supply is to obtain a replacement for ... :-) Good luck with it, and do let us know how you get on ! Arfa |
Finding A Power Supply Schematic
Michael Karas wrote in message
... [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] In article , says... Excellent pictures, thanks. I believe the actual marking code is DF; the R indicates the gain and the G is a prouction lot or date code. My favorite source for arcane marking info: http://www.s-manuals.com Which leads to: http://www.s-manuals.com/smd/df And the datasheet: (watych out for line breaks) http://www.s-manuals.com/pdf/datashe...C_2sd1768s%2C_ 2sd1863%2C_2sd1898_rohm.pdf IF you are in the USA, they are available from Digi-Key (ww.digikey.com) for $.53 each. (Choose USPS First Class Mail for lowest shipping cost.) As a general rule, I dissaprove of replacing parts because they 'look bad'. A few minutes making measurements with a DVM can give a wealth of information. PlainBill THanks for the info. I had also done some research on some other sites and find that there are multiple possibilities for this device marked with a DF. Sanyo NPN 2SD1623 Philips PNP BF621 Siemens PNP BNF21 Rohm NPN 2SD1898 ** ** The part that you located. I agree that this part should not be replaced if it is working. I had done some preliminary checking with the meter and it did not seem to respond with any forward biased junction readings and so I needed to get information as to whether this was some type of FET or a blown BJT transistor. When I get a power cord setup to be able fire up the board I will do some checking. I may also need to rig up a temoprary heatsink for a large diode bridge that gets screwed to part of the case that had to be removed to get at the board. Initial tests can probably avoid that if I just put small loads on the output rails for testing, -- Michael Karas Carousel Design Solutions http://www.carousel-design.com Probably just incidental and irrelevant to the main problem, as it can only get stressed while the SMPS is operational. I've still not seen you state the identity of the supervisor/controller IC/s ? or is it discrete componentry? |
Finding A Power Supply Schematic
On Sun, 26 May 2013 13:08:53 -0700, Michael Karas
wrote: [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] In article , says... Excellent pictures, thanks. I believe the actual marking code is DF; the R indicates the gain and the G is a prouction lot or date code. My favorite source for arcane marking info: http://www.s-manuals.com Which leads to: http://www.s-manuals.com/smd/df And the datasheet: (watych out for line breaks) http://www.s-manuals.com/pdf/datashe...C_2sd1768s%2C_ 2sd1863%2C_2sd1898_rohm.pdf IF you are in the USA, they are available from Digi-Key (ww.digikey.com) for $.53 each. (Choose USPS First Class Mail for lowest shipping cost.) As a general rule, I dissaprove of replacing parts because they 'look bad'. A few minutes making measurements with a DVM can give a wealth of information. PlainBill THanks for the info. I had also done some research on some other sites and find that there are multiple possibilities for this device marked with a DF. Sanyo NPN 2SD1623 Philips PNP BF621 Siemens PNP BNF21 Rohm NPN 2SD1898 ** ** The part that you located. Note that the marking codes seem to be chosen by the manufacturer. Always make sure you are dealing with the same package type. PlainBill |
Finding A Power Supply Schematic
[This followup was posted to sci.electronics.repair and a copy was sent
to the cited author.] In article , says... If available, I would strongly recommend the use of a proper bench isolating transformer when working on this. I'm sure that it is probably a case of grandmothers and egg-sucking as you seem to be saying the right things, but just in case ... Switchers are of course extremely dangerous on a 'raw' line supply. I usually have a variac connected as well. This can be either a help or a hindrance depending on design, but I always initially make the assumption that it is going to be a help, when I don't have a schematic. Although some supplies have UVLO on the control IC, so won't start with a reduced input voltage, it does at least allow you to carry out checks on - for instance - the startup supply, in a safe manner, and without the risk of a Disney-esque fireworks display, when your meter or 'scope probe slips, which it always will sooner or later, depending on how urgent the job is, and how rare the supply is to obtain a replacement for ... :-) Good luck with it, and do let us know how you get on ! Arfa I will post back here when more work on this power supply has happened. Normal workweek obligations force one to set aside tasks like repairing monitors. -- Michael Karas Carousel Design Solutions http://www.carousel-design.com |
Finding A Power Supply Schematic
In article ,
Michael Karas wrote: [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] In article , says... If available, I would strongly recommend the use of a proper bench isolating transformer when working on this. I'm sure that it is probably a case of grandmothers and egg-sucking as you seem to be saying the right things, but just in case ... Switchers are of course extremely dangerous on a 'raw' line supply. I usually have a variac connected as well. This can be either a help or a hindrance depending on design, but I always initially make the assumption that it is going to be a help, when I don't have a schematic. Although some supplies have UVLO on the control IC, so won't start with a reduced input voltage, it does at least allow you to carry out checks on - for instance - the startup supply, in a safe manner, and without the risk of a Disney-esque fireworks display, when your meter or 'scope probe slips, which it always will sooner or later, depending on how urgent the job is, and how rare the supply is to obtain a replacement for ... :-) Good luck with it, and do let us know how you get on ! Arfa I will post back here when more work on this power supply has happened. Normal workweek obligations force one to set aside tasks like repairing monitors. I see that even after all these years, you still haven't got your priorities right 8^} Isaac |
Finding A Power Supply Schematic
On Tuesday, May 28, 2013 9:52:46 PM UTC-7, isw wrote:
... like repairing monitors. I see that even after all these years, you still haven't got your priorities right 8^} Isaac :^) Priorities are just that . . . something that somehow gets set by what we choose to do. Michael Karas |
Finding A Power Supply Schematic
[This followup was posted to sci.electronics.repair and a copy was sent
to the cited author.] In article , says... On Sun, 26 May 2013 13:08:53 -0700, Michael Karas wrote: [This followup was posted to sci.electronics.repair and a copy was sent to the cited author.] In article , says... Excellent pictures, thanks. I believe the actual marking code is DF; the R indicates the gain and the G is a prouction lot or date code. My favorite source for arcane marking info: http://www.s-manuals.com Which leads to: http://www.s-manuals.com/smd/df And the datasheet: (watych out for line breaks) http://www.s-manuals.com/pdf/datashe...C_2sd1768s%2C_ 2sd1863%2C_2sd1898_rohm.pdf IF you are in the USA, they are available from Digi-Key (ww.digikey.com) for $.53 each. (Choose USPS First Class Mail for lowest shipping cost.) As a general rule, I dissaprove of replacing parts because they 'look bad'. A few minutes making measurements with a DVM can give a wealth of information. PlainBill THanks for the info. I had also done some research on some other sites and find that there are multiple possibilities for this device marked with a DF. Sanyo NPN 2SD1623 Philips PNP BF621 Siemens PNP BNF21 Rohm NPN 2SD1898 ** ** The part that you located. Note that the marking codes seem to be chosen by the manufacturer. Always make sure you are dealing with the same package type. PlainBill Well, I received the new capacitors for the monitor power supply and got those installed. The power supply fired right up and produced its 5V STBY output. I then tested the other outputs by connecting the PSON signal on one of the connectors over to the 5V STBY and all of the +5, + 12 and +24 volt rails all came up. I tested the thing on the bench with some load on each output and it works nicely. Unfortunately when the PSU is mated up with the video controller board in the monitor it fails to come up and act like a monitor. The only thing that does appear to work is that the EDID device does provide valid data back out through the D-Sub HD15 connector to a host computer. It shows the proper native monitor ID strings and the correct native resolution. But no other functioning is in operation. Since this thing was given to me for free and the fact that it only supports analog VGA signalling (no DVI connector) I will probably not spend any more time futzing around with it. -- Michael Karas Carousel Design Solutions http://www.carousel-design.com |
Finding A Power Supply Schematic
In article ,
Michael Karas wrote: --snippage -- Since this thing was given to me for free and the fact that it only supports analog VGA signalling (no DVI connector) I will probably not spend any more time futzing around with it. A while back, I acquired a very nice LCD monitor with both VGA and DVI-D interfaces. At the time, the only interface adapter I had was VGA (this is on a Mac which uses an external adapter). Later, I got a DVI-D adapter and cable, and was able to compare the two. Despite my most careful comparisons, using both text and images, I was unable to see any difference in the image quality between the two. VGA is not all that bad. Isaac |
Finding A Power Supply Schematic
[This followup was posted to sci.electronics.repair and a copy was sent
to the cited author.] In article ], says... VGA is not all that bad. Isaac I am inclined to agree that analog VGA can be pretty good. A lot depends upon the quality of the cables, its lengths and how well the video controller outputs are terminated. Since LCD type panels will digitize the analog signal anyway there is also a lot that can be done on a decent monitor regarding how the signal is sampled. In my personal experience with quite a variety of different LCD monitors attached to an almost equally diverse array of different video driver implementations I have both situations. In some instances where an analog VGA to DVI direct comparison was done there was virtually no discernable difference. On the other hand there were examples where there was a distinct difference in the displayed image - even on a monitor that had both DVI and analog VGA connections fed the same content from the same video controller. -- Michael Karas Carousel Design Solutions http://www.carousel-design.com |
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