comparison: content/dell2407.rst
content/dell2407.rst
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| 126:521c35556177 | 128:aba381b2bac9 |
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| 17 | 17 |
| 18 The enclosure is reasonably easy to disassemble: 4 screws on the back, then the | 18 The enclosure is reasonably easy to disassemble: 4 screws on the back, then the |
| 19 usual plastic clips to unclipse all around the enclose. The result is a very | 19 usual plastic clips to unclipse all around the enclose. The result is a very |
| 20 standard view for these LCD monitors: a big metallic enclosure: | 20 standard view for these LCD monitors: a big metallic enclosure: |
| 21 | 21 |
| 22 .. image:: {static}images/dell2407wfp/back.jpg | 22 .. image:: {static}/images/dell2407wfp/back.jpg |
| 23 :alt: Back of the Dell 2407WFP | 23 :alt: Back of the Dell 2407WFP |
| 24 | 24 |
| 25 | 25 |
| 26 When removed, the also very classic view on the boards: | 26 When removed, the also very classic view on the boards: |
| 27 | 27 |
| 28 .. image:: {static}images/dell2407wfp/back-pcbs.jpg | 28 .. image:: {static}/images/dell2407wfp/back-pcbs.jpg |
| 29 :alt: PCBs of the Dell 2407WFP | 29 :alt: PCBs of the Dell 2407WFP |
| 30 | 30 |
| 31 Since there is nothing at all, the first and most probable place to start | 31 Since there is nothing at all, the first and most probable place to start |
| 32 looking is the PSU: | 32 looking is the PSU: |
| 33 | 33 |
| 34 .. image:: {static}images/dell2407wfp/psu.jpg | 34 .. image:: {static}/images/dell2407wfp/psu.jpg |
| 35 :alt: PSU of the Dell 2407WFP | 35 :alt: PSU of the Dell 2407WFP |
| 36 | 36 |
| 37 | 37 |
| 38 Diagnostic | 38 Diagnostic |
| 39 ========== | 39 ========== |
| 40 | 40 |
| 41 Inspecting the PSU, the first culprit (and the probable origin of the failure) | 41 Inspecting the PSU, the first culprit (and the probable origin of the failure) |
| 42 is pretty obvious: | 42 is pretty obvious: |
| 43 | 43 |
| 44 .. image:: {static}images/dell2407wfp/badcap.jpg | 44 .. image:: {static}/images/dell2407wfp/badcap.jpg |
| 45 :alt: Bad cap on the Dell 2407WFP | 45 :alt: Bad cap on the Dell 2407WFP |
| 46 | 46 |
| 47 This one is dead, right, but the question is if it died alone (very unlikely) | 47 This one is dead, right, but the question is if it died alone (very unlikely) |
| 48 or if it took a series of other parts with it. | 48 or if it took a series of other parts with it. |
| 49 | 49 |
| 50 Using the multimeter in diode mode, I immediately found a dead fuse (good sign, | 50 Using the multimeter in diode mode, I immediately found a dead fuse (good sign, |
| 51 might have done its job and protect some other parts on the PSU... or not), but | 51 might have done its job and protect some other parts on the PSU... or not), but |
| 52 also a dead MOSFET (Q651, the one on the PFC stage) and maybe more: | 52 also a dead MOSFET (Q651, the one on the PFC stage) and maybe more: |
| 53 | 53 |
| 54 .. image:: {static}images/dell2407wfp/dead-parts.jpg | 54 .. image:: {static}/images/dell2407wfp/dead-parts.jpg |
| 55 :alt: First batch of dead parts on the Dell 2407WFP PSU | 55 :alt: First batch of dead parts on the Dell 2407WFP PSU |
| 56 | 56 |
| 57 At this point, finding datasheets for the controller chips on this board looked | 57 At this point, finding datasheets for the controller chips on this board looked |
| 58 like a good idea. Most of the time, these PSU designs are very close to the | 58 like a good idea. Most of the time, these PSU designs are very close to the |
| 59 application circuit described in the datasheets. | 59 application circuit described in the datasheets. |
| 76 quest for fixes. Which led me to a PDF with the full schematic of the PSU | 76 quest for fixes. Which led me to a PDF with the full schematic of the PSU |
| 77 (which is in fact a BenQ brand). | 77 (which is in fact a BenQ brand). |
| 78 | 78 |
| 79 The first stage of the PSU, around the L6561D controller looks like: | 79 The first stage of the PSU, around the L6561D controller looks like: |
| 80 | 80 |
| 81 .. image:: {static}images/dell2407wfp/psu-schematic-p1.svg | 81 .. image:: {static}/images/dell2407wfp/psu-schematic-p1.svg |
| 82 :alt: Schematic of the first (PFC) stage of the PSU of the Dell 2407WFP | 82 :alt: Schematic of the first (PFC) stage of the PSU of the Dell 2407WFP |
| 83 | 83 |
| 84 And the regulation stage: | 84 And the regulation stage: |
| 85 | 85 |
| 86 .. image:: {static}images/dell2407wfp/psu-schematic-p2.svg | 86 .. image:: {static}/images/dell2407wfp/psu-schematic-p2.svg |
| 87 :alt: Schematic of the second (PWM + secondary) stage of the PSU of the Dell 2407WFP | 87 :alt: Schematic of the second (PWM + secondary) stage of the PSU of the Dell 2407WFP |
| 88 | 88 |
| 89 | 89 |
| 90 For the record, here are the typical application schematics from datasheets: | 90 For the record, here are the typical application schematics from datasheets: |
| 91 | 91 |
| 92 .. image:: {static}images/dell2407wfp/L6561-AN.svg | 92 .. image:: {static}/images/dell2407wfp/L6561-AN.svg |
| 93 :alt: Typical application schematic of the L6561 PFC controller. | 93 :alt: Typical application schematic of the L6561 PFC controller. |
| 94 | 94 |
| 95 As tou can see, it is very similar to the first page of the schematic above. | 95 As tou can see, it is very similar to the first page of the schematic above. |
| 96 This later have the extra power button management circuit, and a few details | 96 This later have the extra power button management circuit, and a few details |
| 97 and compenent values are different, but overall, a very close application of | 97 and compenent values are different, but overall, a very close application of |
| 98 the typical application schematic (as expected). | 98 the typical application schematic (as expected). |
| 99 | 99 |
| 100 And for the PMW stage, I could not find such a typical application circuit more | 100 And for the PMW stage, I could not find such a typical application circuit more |
| 101 advanced than this very basic one (from the datasheet): | 101 advanced than this very basic one (from the datasheet): |
| 102 | 102 |
| 103 .. image:: {static}images/dell2407wfp/NCP1200A.svg | 103 .. image:: {static}/images/dell2407wfp/NCP1200A.svg |
| 104 :alt: Typical application schematic of the NCP1200A PWM controller. | 104 :alt: Typical application schematic of the NCP1200A PWM controller. |
| 105 | 105 |
| 106 However some interesting details and circuit improvements can be found in this | 106 However some interesting details and circuit improvements can be found in this |
| 107 `application note <https://www.onsemi.com/pub/Collateral/AND8069-D.PDF>`_. | 107 `application note <https://www.onsemi.com/pub/Collateral/AND8069-D.PDF>`_. |
| 108 | 108 |
| 145 | 145 |
| 146 So I decided to replace IC651 (the PFC controller, L6561D). And since I had not | 146 So I decided to replace IC651 (the PFC controller, L6561D). And since I had not |
| 147 that much spare STP10NK60ZFP transistor for Q651, I decided to try first with | 147 that much spare STP10NK60ZFP transistor for Q651, I decided to try first with |
| 148 some junk parts from a PCB laying around, on which are many APT8075BN: | 148 some junk parts from a PCB laying around, on which are many APT8075BN: |
| 149 | 149 |
| 150 .. image:: {static}images/dell2407wfp/junk_pcb.jpg | 150 .. image:: {static}/images/dell2407wfp/junk_pcb.jpg |
| 151 :alt: The PCB from which I took an APT8075BN as test Q651 replacement. | 151 :alt: The PCB from which I took an APT8075BN as test Q651 replacement. |
| 152 | 152 |
| 153 The leads qre not exactly the same spacing, but I managed to do something: | 153 The leads qre not exactly the same spacing, but I managed to do something: |
| 154 | 154 |
| 155 .. image:: {static}images/dell2407wfp/apt8075bn.jpg | 155 .. image:: {static}/images/dell2407wfp/apt8075bn.jpg |
| 156 :alt: The APT8075BN used as test Q651 replacement. | 156 :alt: The APT8075BN used as test Q651 replacement. |
| 157 | 157 |
| 158 | 158 |
| 159 Which resulted in a rather acrobatic setup: I did not want to fight to make it | 159 Which resulted in a rather acrobatic setup: I did not want to fight to make it |
| 160 fit nicely enough that I can screw it on the heatsink (plus it is not | 160 fit nicely enough that I can screw it on the heatsink (plus it is not |
| 162 insulator. I have some, but finding them would have required a bit fo digging | 162 insulator. I have some, but finding them would have required a bit fo digging |
| 163 in my overcrowded empire of dirt). | 163 in my overcrowded empire of dirt). |
| 164 | 164 |
| 165 The resulting setup looks like: | 165 The resulting setup looks like: |
| 166 | 166 |
| 167 .. image:: {static}images/dell2407wfp/psu-repaired-1.jpg | 167 .. image:: {static}/images/dell2407wfp/psu-repaired-1.jpg |
| 168 :alt: The APT8075BN used as test Q651 replacement. | 168 :alt: The APT8075BN used as test Q651 replacement. |
| 169 | 169 |
| 170 However, before applying power again, I checked all the silicon components once | 170 However, before applying power again, I checked all the silicon components once |
| 171 more. And I discovered (what I missed the first time) that Q653 was also dead. | 171 more. And I discovered (what I missed the first time) that Q653 was also dead. |
| 172 | 172 |
| 173 The problem was I had no proper SOT23 replacement part for it. THe good news is | 173 The problem was I had no proper SOT23 replacement part for it. THe good news is |
| 174 I do have a few 2N7000 that can be used, but are TO92 packages. | 174 I do have a few 2N7000 that can be used, but are TO92 packages. |
| 175 So I did a bit of surgery: | 175 So I did a bit of surgery: |
| 176 | 176 |
| 177 .. image:: {static}images/dell2407wfp/hack.jpg | 177 .. image:: {static}/images/dell2407wfp/hack.jpg |
| 178 :alt: The APT8075BN used as test Q651 replacement. | 178 :alt: The APT8075BN used as test Q651 replacement. |
| 179 | 179 |
| 180 | 180 |
| 181 Fixed | 181 Fixed |
| 182 ----- | 182 ----- |
| 185 And stays alive when I draw current (1A). | 185 And stays alive when I draw current (1A). |
| 186 | 186 |
| 187 I plugged it back in the monitor, the green LED lit as well as the display | 187 I plugged it back in the monitor, the green LED lit as well as the display |
| 188 itself showing the 'No signal detected' message box! | 188 itself showing the 'No signal detected' message box! |
| 189 | 189 |
| 190 .. image:: {static}images/dell2407wfp/alive-1.jpg | 190 .. image:: {static}/images/dell2407wfp/alive-1.jpg |
| 191 :alt: It's alive! | 191 :alt: It's alive! |
| 192 | 192 |
| 193 I replaced the temporary Q651 transistor with the proper reference, checked the | 193 I replaced the temporary Q651 transistor with the proper reference, checked the |
| 194 result, then put everything back together. | 194 result, then put everything back together. |
| 195 | 195 |
| 196 .. image:: {static}images/dell2407wfp/alive.jpg | 196 .. image:: {static}/images/dell2407wfp/alive.jpg |
| 197 :alt: It's alive! | 197 :alt: It's alive! |
| 198 | 198 |
| 199 | 199 |
| 200 However, before closing the box, I did a few tests and measurements, for the | 200 However, before closing the box, I did a few tests and measurements, for the |
| 201 fun. I found the reason for the properly working 19v rail when unloaded at the | 201 fun. I found the reason for the properly working 19v rail when unloaded at the |
