# HG changeset patch # User David Douard # Date 1506032002 -7200 # Node ID 9296d8c2339a099c1f66cd8cba6af59cf1edf0b5 # Parent 76d5c4108e51af7b5b9612d5e0c2d71a21552f11 [zr24w] blog post about the HP ZR24W PSU repair diff -r 76d5c4108e51 -r 9296d8c2339a content/HPZR24W.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/content/HPZR24W.rst Fri Sep 22 00:13:22 2017 +0200 @@ -0,0 +1,195 @@ +===================== + HP ZR24W PSU Repair +===================== + +:Author: David Douard +:Category: Electronics +:Tags: ZR24W, PSU, PWB-1336-02, TPS-10036 + +A friend of mine had a problem with his (a bit old) 24" HP monitor: the device +was working properly, but only for a while (few minutes at most). + +Looked like a good candidate for a quick repair, problem being most probably +bad caps are so. + +The first step was to find out how to disassemble the down thing, since these +"modern" things are not designed to be serviced and have no screw, only plastic +clips which are so easy to break. + +Whatever, I finally succeded in opening the box (with only one or 2 broken +clips). + +Overview +======== + +Inside the beast, the usual stuff under the shields: + +- a PSU, +- a main controller board, +- an LCD driver board, and the monitor being a bit old, +- a blacklight HV driver board. + + +.. image:: {filename}images/ZR24W/back.jpg + :alt: Back of the HP ZR24W + +First thing, to make sure the problem comes from the PSU, I powered the monitor +from my bench power supplies. I used one output of my HP E3648A to generate the +19V rail that powers the backlight. It was a bit short (CC limited at 16V), but +enough to power the backlight. The second output was used to produce the 12V, +and the 5V was generated by my very old home made PSU. + +.. image:: {filename}images/ZR24W/ext_power.jpg + :alt: Testing the display with my bench PSU. + +The monitor was working fine when powered from these PSUs, so the problem was, +indeed, this Tatung PWB-1336-02 switching PSU: + +.. image:: {filename}images/ZR24W/psu_top.jpg + :alt: Top of the Tatung PWB-1336-02 PSU + +.. image:: {filename}images/ZR24W/psu_bottom.jpg + :alt: Bottom view of the Tatung PWB-1336-02 PSU + +The design is nice and clean. Electrolytic caps however are not the best ones +(mostly Lelong ones I think), which is not really a surprise in this kind of +device. + +At first sight, nothing strike the eye, no leaky cap, no burnt resistor or +PCB... + +Not a 10mn fix, in the end. + +The PSU generates 3 voltages: + +- 5V @2.7A +- 12V @0.8A +- 19V @3.2A + + +Finding the problematic power rail +================================== + +There is a hard switch on the PSU, next to the IEC socket, and When the power +is on, the 5V is hot, wether the monitor is on or in standby. + +When the display is powered on, the 2 other voltages are started. + +The pin 10 on the cable between the PSU and the main CPU board is dedicated +to the "power saving" state. It must be high (at 5V, which is always present) +to enable the 2 other voltages. + +Note that there are 2 other pins dedicated to power management (pin 11 and 12, +marked as "On/Off" and "Vadj"). But these are directly routed to the backlight +board and take no part in the PSU management. + + +My first test has been to plug my cheap `electronic load +<{filename}/ZPB30A1.rst>`_ on the 5V with the 2 other voltages stopped. + +And I could reliably sink 3A from there. So the problem must be on one of the 2 +other rails. + +But I also could sink the max amperage from the 2 other power rails (1A from +the 12V and 3.5A from the 19V)... + +Ok, so each power rail seems to work fine alone. + +But when I sink current from the 5V rail while the 2 other voltages are up, +then the PSU fails after a short while. + +I've tried to probe a bit the switching curves using my Rigol DS1054, but the +PSU being "hot" (around 400V), and having no isolation transformer, I could not +probe the signals correctly (using 2 probe and displaying the A-B curve, which +is some kind of a joke on the Rigol, since you cannot hide the A and B curves: +the curve substraction is purely computed from displayed curve. When I found +how useless this was on the Rigol, I had not enough energy to extract my old +`Tek 2445A <{filename}/TeK2445.rst>`_ from under the pile of test equipment +stowed in the closet...) + + +A glimpse at schematics +----------------------- + +At this point, I needed to try to understand a bit the schematic. I wasn't even +sure the problem came from this side of the PSU, it could also be a problem in +the "isolated" part (bad caps, bad optocoupler, bad voltage reference...). I +had checked the main caps, and they seemed to be ok (not quality japanese +brands, but still the correct value and low ESR). + + +On the live part, before the transformers, there are 2 chips : + +- a TNY279PN_ dedicated to the 5V rail +- a CM6807_ for the 19V rail + +The 12V is produced from the 19V rail by a small DC to DC converter (FP6185_). + +In fact, this PSU design is almost just the 2 application circuits (found in +their respective datasheets) merged together. + +The noticable points are: + +- The TNY279PN DC input can be come from either the input bridge rectifiers + (via a diode and a thermistor), or, when powered, by the DC produced by the + CM6807 via the PFC circuit. So when the CM6807 is down (when the monitor is + in standby), the DC input for the TNY279 is around 318V, but when the monitor + is on, the CM6807's PFC circuit rise this voltage to almost 400V. + +- The bias winding, normally used to power the TNY279 (to allow a very low + no-load power consumption, datasheet says <50mw) also powers the CM6807. + + A funny side effect of this design is that the CM6807 cannot be started if + there is no load on the 5V rail: in this case, the auxiliary voltage of the + transformer managed by the TNY279 is not enough to start the CM6807. + + +The application circuits are as follow: + +.. image:: {filename}images/ZR24W/tny279_app_circuit.svg + :alt: Example application circuit for the TNY279PN controller (from the `datasheet `_) + +.. image:: {filename}images/ZR24W/CM6807_app_circuit.svg + :alt: Example application circuit for the CM6807 controller (from the `datasheet `_) + +In this PSU, the input DC of the TNY279 (the point just before R5 in the app +circuit) in connected just behind the PFC circuit, i.e. just after the D2 diode +of the CM6807 app circuit. + +In order for the PSU to generate the 5V rails even when the CM6807 is off, +there is derivated DC input path, from the bridge rectifier to the input DC +rail, consisting in a diode (D922 on the PCB) followed by a thermistor (R915): + +.. image:: {filename}images/ZR24W/input_DC.jpeg + :alt: Input DC showing both paths (yellow: via the PFC, red: the alternate + path when power saving is on). + + +Finally, the culprit +-------------------- + +While testing the PSU powering the CM6807 from an external source, I notices +another strange behaviour: the TNY279 enters a failure as soon as I sink +current from the 5V rail, but it remains faulty as long as I let the CM6807, +thus the PFC running, and the input DC at 400V (instead of 318V when the PFC is +not activated).. + +At this point, I though there is not way the problem can come from the 5V +regulation loop, neither from the CM6807 circuit, so the only culprit left +would be either the TNY279PN or a component close to it, a cap (especially the +BP/M one), a diode or a resistor. So I tested these parts (again, to be fair), +and I replaced the cap connected to the BP/M pin. With no improvement, the only +remaining faulty part must be the TNY279PN. + +So I decided to buy a couple of them from RS, and 2 days later I replaced it, +which did fix the PSU. + +What a tricky half-failing part! + + + + +.. _TNY279PN: + https://www.power.com/sites/default/files/product-docs/tny274-280.pdf +.. _CM6807: http://www.championmicro.com.tw/datasheet/Analog%20Device/CM6807.pdf +.. _FP6185: http://www.feeling-tech.com.tw/km-master/ezcatfiles/cust/img/img/24/fp6185drv02-g1.pdf diff -r 76d5c4108e51 -r 9296d8c2339a content/images/ZR24W/CM6807_app_circuit.svg --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/content/images/ZR24W/CM6807_app_circuit.svg Fri Sep 22 00:13:22 2017 +0200 @@ -0,0 +1,15738 @@ + + + +image/svg+xmlR48 +47K +1 +2 +D16(20A/150V)DIODE SCHOTTKY +1 +2 +3 +R17 +10 +1 +2 +D101N4001 +1 +2 +C10680uF/35V +1 +2 +C2847uF/25V +1 +2 +C3 +1000PF +1 +2 +D13 +1N4935 +1 +2 +ZD4 +Z.D 27V +1 +3 +U2 +TSM103 +1 +2 +4 +6 +7 +3 +8 +5 +R35 +220K +1 +2 +L2 +FR16*12*8 +4 +1 +3 +2 +C51 +1UF +1 +2 +L1PIN +1L +R131 +68k +1 +2 +16T +C50NC +1 +2 +R52 +NC +1 +2 +B002 +V+I ++24V +R3 +1.5M +1 +2 +R42 +12K +1 +2 +C19 +105PF +1 +2 +R37 +3K +1 +2 +R13 +33k +1 +2 +R111 +2.7M +1 +2 +N1PIN +1N +R11 +2.7M +1 +2 +C34 +102pF +1 +2 +Iac +R39 +470 +1 +2 +PWMTrifault +R24 +0.39 2W +1 +2 +C17100uF +1 +2 +R21 +10 +1 +2 +C32 +NC +1 +2 +R6 +1.5M +1 +2 +R46 +3.9K +1 +2 +R53 +22k +1 +2 +C23 +0.1UF +1 +2 +R38 +620 +1 +2 +R2947K +1 +2 +D14 +BAW56 +2 +3 +1 +R190 +1 +2 +C26 +0.1UF(104) +1 +2 +R008-1 +68K +1 +2 +F1 +3.15A,250V +1 +2 +Q9SPP20N60C3 +3 +2 +1 +C15 +470PF +1 +2 +R18 +2.2M +1 +2 +D12 +1N4148 +1 +2 +R50 +11K +1 +2 +C30 +NC +1 +2 +L5 +MPP/1.2mH +2 +1 +3.5*6*1.2 +Iac +R25 +47K +1 +2 +Q13NC +3 +1 +2 +D111N4001 +1 +2 +C16 +0.1UF +1 +2 +HSA1HS +1 +212 +R5 +22k +1 +2 +FGJ3 +11 +R49 +NC +1 +2 +Q5 +GMBTA44 +1 +2 +3 +Boostfollower +R30 +0 +1 +2 +R7 +4.7M +1 +2 +Q11 +2N7002 +2 +3 +1 +R15 +1M +1 +2 +Q7FCP11N60 +3 +2 +1 +R160 +1 +2 +R23 +220K +1 +2 +R31 +4.7K +1 +2 +R34 +1M +1 +2 +RT12.5 +1 +2 +D71N4148 +1 +2 +L3 +OR12*6*4 +4 +1 +3 +2 +ZD5 +Z.D 15V +1 +3 +D91N4148 +1 +2 +VCC +Q14NC +3 +1 +2 +D2MBR860 +1 +2 +3.5*9*1.3 +Q10 +2222 +2 +3 +1 +1243 +PC1 +PC817C +C20 +0.1UF +1 +2 +R43 +1K +1 +2 +R26 +0.27 2W +1 +2 +R45 +0 +1 +2 +D8 +PR2007 +1 +2 +R27 +0.0045 +1 +2 +GNDJ1 +11 +C24 +0.1UF +1 +2 +R531 +750 +1 +2 +R341 +1M +1 +2 +16T +Q111 +2N7002 +2 +3 +1 ++24VJ3 +11 +6T +FLY1 +ZD4 +Z.D 27V +1 +3 +D61N4148 +1 +2 +D15(20A/150V)DIODE SCHOTTKY +1 +2 +3 +TA1 +Pot-C3319/PC44 +2 +5 +4 +1 +7 +3 +R36 +51 +1 +2 +FLY2 +U1CM6807 +2 +1 +3 +4 +5 +6 +7 +8 +9 +10IACGNDIsenseVEAOVFBV+IPwmTrifaultVCCPFC OUTPWM OUT +R40 +22K +1 +2 +FG1PIN +1FG +R8 +47K +1 +2 +J1PIN +1 +R51 +NC +1 +2 +C13 +684 +1 +2 +C5 +0.47UF/450V +1 +2 +HSA2HS +11 +B001 +C22 +10pF(100) +1 +2 +R44 +220K +1 +2 +3.5*9*1.3 +-+ +D1KBP206G +2 +1 +3 +4 ++24V +R14 +2.2M +1 +2 +R22 +47 +1 +2 +C21 +0.1UF +1 +2 +C25 +1UF +1 +2 +C52 +222 +1 +2 +4T +C11680uF/35V +1 +2 +R351 +680K +1 +2 +C7100uF/400V +1 +2 +VCC +R151 +1M +1 +2 +R54 +NC +1 +2 +R33NC +1 +2 +R4110K +1 +2 +C1 +0.22UF +1 +2 +R28 +NC +1 +2 +RT2NC +1 +2 +C27 +470nF(474) +1 +2 +ZD6 +NC +1 +3 +Radd +NC +1 +2 +R47 +4.7K +1 +2 +C31 +NC +1 +2 +VCC +R55NC +2 +1 +B001 +C191 +105PF +1 +2 +J2GND +11 + \ No newline at end of file diff -r 76d5c4108e51 -r 9296d8c2339a content/images/ZR24W/back.jpg Binary file content/images/ZR24W/back.jpg has changed diff -r 76d5c4108e51 -r 9296d8c2339a content/images/ZR24W/ext_power.jpg Binary file content/images/ZR24W/ext_power.jpg has changed diff -r 76d5c4108e51 -r 9296d8c2339a content/images/ZR24W/input_DC.jpeg Binary file content/images/ZR24W/input_DC.jpeg has changed diff -r 76d5c4108e51 -r 9296d8c2339a content/images/ZR24W/input_DC.kra Binary file content/images/ZR24W/input_DC.kra has changed diff -r 76d5c4108e51 -r 9296d8c2339a content/images/ZR24W/psu_bottom.jpg Binary file content/images/ZR24W/psu_bottom.jpg has changed diff -r 76d5c4108e51 -r 9296d8c2339a content/images/ZR24W/psu_top.jpg Binary file content/images/ZR24W/psu_top.jpg has changed diff -r 76d5c4108e51 -r 9296d8c2339a content/images/ZR24W/tny279_app_circuit.svg --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/content/images/ZR24W/tny279_app_circuit.svg Fri Sep 22 00:13:22 2017 +0200 @@ -0,0 +1,2621 @@ + + + +image/svg+xmlD S S BP/M +EN/UV +L1 1 mH D1 1N4007 RV1 275 VAC F1 3.15 A D2 1N4007 C1 6.8 +μ +F 400 V C6 1 +μ +F 60 V C2 22 +μ +F 400 V C10 1000 +μ +F 25 V C5 2.2 nF 250 VAC C11 100 +μ +F 25 V +12 V, 1 A85 - 265VACRTN +C7 100 nF 50 V U1TNY278PNC4 10 nF 1 kV VR1 P6KE150A NC 8 6 4 T1 2 5 1 3 D5 1N4007GP D6 UF4003 D7 BYV28-200 U2 PC817A VR2 1N5255B 28 V VR3 BZX79-C11 +11 V C7 is used to adjust U1 current limit. See circuitdescription*R5 and R8 are optional components R5* 3.6 M +Ω +R3 47 +Ω +1/8 W R4 2 k +Ω +1/8 W R6 390 +Ω +1/8 W R7 20 +Ω +R8* 21 k +Ω +1% R1 1 k +Ω +R2 100 +Ω +D3 1N4007 D4 1N4007 +L2 Ferrite Bead 3.5 × 7.6 mm +PI-4244-111708 +† † +TinySwitch-III + \ No newline at end of file