Projector SMPS help - Page 1
Forum section: electronics / general

author: MikeCL
author_rank: Contributor
timestamp: May 15, 2013, 04:24:40 pm
content: I was wondering if anyone could help me out with this SMPS from a infocus projector.Long story short I get no low voltage output at all but from the filter caps I have 164 VDC but the PFC is not getting any power to switch up to raise the voltage up to 390V.

author: SeanB
author_rank: Super Contributor
timestamp: May 15, 2013, 05:11:58 pm
content: What is the value of that resistor between C205 and C208, possibly it is open circuit, or C208 is leaky. That or the controller IC is shorted, or the chopper chip is dead. All thease will load down the power on circuit and have no go as the result. My preference is the resistor and capacitor first, they do tend to fail especially as the capacitor is right next to a very hot resistor.

author: MikeCL
author_rank: Contributor
timestamp: May 15, 2013, 07:56:44 pm
content: that resistor is 0.36 Ohm 2WC208 is 22uF 50VHere is the backThe optoisolator are FOD817BW I get reading on one side but nothing on the other side.. and On the other one I get no reading at all.Ic204 I get 2.8V on pins 3 & 4

author: MikeCL
author_rank: Contributor
timestamp: May 16, 2013, 03:54:36 am
content: MR4010 IC seems like the gate is stuck on and conducting which would account for it going to 60 C in less then 3 minutes with no load.I will have to get a replacement and check.

author: SeanB
author_rank: Super Contributor
timestamp: May 16, 2013, 05:39:27 am
content: Change the cap, resistor and diode connected to pin 4 first, if the capacitor is leaky it will never charge to the unlock voltage, and the start supply will keep trying to charge it and heat up the die. If the pass device was shorted or leaky the fuse would have left long ago violently. Check by replacement, and check if there is a short voltage pulse across it when power is applied. If the resistor or diode is open the power supply will give 3 short single pulses then stay in shutdown. If diode is shorted or leaky then it will never power up. I suspect the actual circuit is not quite as per the appnote, looks like they are using extra zener diodes and transistors there, possibly for protection.As a test apply around 15V via a 100R 1Wresistor to the pin 4 capacitor and see if the current drawn is not too high ( more than 10V across the resistor) with the board not powered. This then will allow you to check both IC's are working, the PFC will be generating very short pulses to the PFC MOSFET, and the main controller will be trying to operate.

author: MikeCL
author_rank: Contributor
timestamp: May 16, 2013, 05:44:47 am
content: Which part are you talking about? IC204 or the MR4010?

author: SeanB
author_rank: Super Contributor
timestamp: May 16, 2013, 06:44:36 am
content: IC201, this is the power supply for the whole unit primary side.Have you checked the output for short circuits, if the diodes are short circuit it will stay in start up as well from the current limiting.

author: retiredcaps
author_rank: Super Contributor
timestamp: May 16, 2013, 06:55:34 am
content: Coincidence?http://www.badcaps.net/forum/showthread.php?t=28667

author: MikeCL
author_rank: Contributor
timestamp: May 16, 2013, 06:59:51 am
content: Quote from: SeanB on May 16, 2013, 06:44:36 amWell I ordered two New MR4010's I'm going to have to check them when they get here which is going to be a little while and see how they compare to the old one.

author: MikeCL
author_rank: Contributor
timestamp: May 16, 2013, 07:02:30 am
content: Quote from: retiredcaps on May 16, 2013, 06:55:34 amNope I was asking around, only two sites out of like 5 I posted at gave solid info this and badcaps.. I was kinda on my own since no one has any info really on these boards but plenty for the older Infocus models.

author: SeanB
author_rank: Super Contributor
timestamp: May 16, 2013, 07:10:41 am
content: Change the caps on the startup supply as well with the IC, it will have been well toasted from the nice hot IC and power resistor next to it over the years.

author: MikeCL
author_rank: Contributor
timestamp: May 16, 2013, 07:12:47 am
content: Quote from: SeanB on May 16, 2013, 07:10:41 amYeah I'm replacing all of the caps plus the IC but the projector is not that old about a year old. I'm thinking a power spike might of taken it out.. I mean I found no info at all searching.. it was all about the older models which had totally different power supplies then me.

author: MikeCL
author_rank: Contributor
timestamp: May 25, 2013, 11:51:11 pm
content: the cap replacement did not work nor did replacing IC201, so I'm wondering here how do I check the transformer which is T201 on the board it's got 4 legs on what seems to be the primary side and 6 legs on the secondary side.

author: MikeCL
author_rank: Contributor
timestamp: May 26, 2013, 05:53:58 pm
content: I checked NTC102 and the 3W 0.36 Ohm resistor and that all checks out fine.

author: MikeCL
author_rank: Contributor
timestamp: August 13, 2013, 08:33:22 pm
content: The output transformer I've never seen one with 4 pins on the primary and 6 pins on the secondary side, anyways I noticed all the pins on the secondary side show S/C when I check with my meter.

author: dr_p
author_rank: Frequent Contributor
timestamp: August 19, 2013, 07:37:05 am
content: The controller driving the power transistor is on the "hot" side, so it's power supply is also "hot" (non isolated from mains). So the transformer winding that powers the IC has to be on the "hot" side of the transformer (the primary side). It's also that way in the example schematic you gave in post #4.You can't conclude the secondary windings are S/C with a regular multimeter. They might be S/C, but probably not. The 6 secondary pins and the apparently shorted windings means all the secondary voltages generated are non isolated from each other. It's like one secondary with multiple intermediate taps. So I would expect multiple output voltages from this PSU.Have you tried replacing the optos?

author: MikeCL
author_rank: Contributor
timestamp: August 19, 2013, 08:12:23 am
content: I tested the optos and they are both fine.

author: Psi
author_rank: Super Contributor
timestamp: August 19, 2013, 08:26:22 am
content: If you're happy with the condition of the caps I would start testing the smd and small signal diodes.Projectors run hot, especially when people forget to clean the air filters.The heat take its toll on the caps first and then on any under-rated signal diodes which just can't handle their rated power at +30 above ambient for more than a few years.No-one suspects the tiny signal diodes but when it comes to projector power supplies i've seen more than a few fail due to them frying.Checking for shorted diodes with a meter is a quick and easy check you can do without having to unsolder any.You can also test in-circuit that each is behaving more or less like a diode using the dmm diode function,but unsoldering maybe needed depending on the circuit and how the diode is used.

author: MikeCL
author_rank: Contributor
timestamp: August 19, 2013, 02:26:27 pm
content: Quote from: Psi on August 19, 2013, 08:26:22 amIn the case of this projector it uses no filters for ease of useI have no problems checking the diodes I just want to make sure I'm checking the correct diodes..A lot of them read both ways but I'm not sure the type of diodes they are but I included some pictures of some in questionhttp://imageshack.us/a/img541/3484/nvzx.jpghttp://imageshack.us/a/img818/1756/r6ab.jpghttp://imageshack.us/a/img716/4139/nvul.jpghttp://imageshack.us/a/img809/2961/jd25.jpg

author: MikeCL
author_rank: Contributor
timestamp: August 19, 2013, 02:52:38 pm
content: OK I think Q602 & Q603 are both transistors they have the marking M3A and M4A

author: Anks
author_rank: Frequent Contributor
timestamp: August 19, 2013, 04:20:31 pm
content: Just for note even though I doubt the transformer is short. You can test for a shorted winding with a neon bulb connected to winding and a small battery. You connect the battery to a winding and release this causes a kick to be generated at the other windings and will light your neon lamp for a second (just like and ignition coil). If there is a shorted winding the short will consume the generated current and the lamp will remain dead.ps Don't try this in circuit.

author: MikeCL
author_rank: Contributor
timestamp: August 19, 2013, 04:22:42 pm
content: Well I don't have a neon bulb anywaysI was just taking a look at CY201 on the board right now I don't know what the cap value is, but it's showing open, but I can read the 105K cap next to it just fine.

author: Psi
author_rank: Super Contributor
timestamp: August 20, 2013, 12:13:38 am
content: It will be 2,200 pFIt's probably ok, testing continuity of caps in circuit only provides useful info if its shorted.