PSU problem Infocus 5700 - heat up caps works

[dodgey]

Hi all, I have an Infocus Screenplay 5700 projector with a PSU problem. It fails to startup unless I blast the power supply board with a hair dryer for 30 seconds or so. Then it runs just fine, until I power it off.

This, I have learnt , means I have ageing cap/s that are on their way out, and the extra heat helps them reach their rated capacity. I also understand these are my "startup" capacitors.

I'm about to order a bunch of caps and replace them - but I'd like to avoid replacing the larger ones unless nesc as they are quite costly and hard to get hold of. Not to mention I'm not looking forward to desoldering them. I also want to do as little soldering as possible as I don't want to destroy a PJ that works, albeit with the aid of a hair dryer.

My soldering is fine, but I did have quite a tough time removing the one cap I have already done (was not the cure) so I want to minimise this.

Pictures to follow below...

So my question is (after looking at the board pics below)

1) Is there a specific area that is most likely to be the startup / guilty caps? i.e. the cluster on the right of 680uf caps 16v
2) Or, is the giant 450v 270uf cap the more likely candidate?
3) Also - I can't test the board in situ as the case has a series of interlocks that are hard to bypass, and the motherboard plugs into the chassis with a slot connector - i.e. no cable - so with the mainboard installed I can't get to the PSU. If I could I'd apply heat carefully to each cap until it started up!
4) If I take the PSU out (as I have done) - and plug it into power, of course I could take meter readings to check each output, but they are not labelled - and there is a large multipin connector that comes off the PSU and I have no idea of the pinouts - so in essence I don't know what I'm looking for
5) Is it possible it could be the small blue square caps - one is right by the FETS / transistors which would have soacked up a load of heat - it is marked u1M400

I've resistance metered the caps on board - which is not ideal. They all climbed slowly, until I got bored and disconnected. None of them ever got to max - they just climbed slowly and consistenly. One small 100uf cap only climbed to "14" so I swapped it out, but it turned out fine - obv. the other circuitry was interfering.

(for reference - before heating it up - the projector fans spin very slowly and the PSU produces fast regular clicks)







I can easily add any more pics that might be of help.

[vtech]

Not familiar with the specific circuit but I can give you a bit of info based on my experience with chopper circuits;
Based on your description, (the ticking sound), it is definitely in the start up circuit. What you hear is the circuit's unsuccessful attempt to start the initial oscillation which resonates as a "tick" sound in the txformer core.
More often than not, the start up cap issues are actually related to smaller/smallest value electrolytics. It may be difficult to pinpoint w/out the diagram, but look for smallest values first ( lets say anything from 100ųf down)only Electrolytics though. Doubt if you have any big cap issue here?
Keep in mind that "heat induced/healed" problems could be a connection issue rather than a cap or even a semiconductor? Also, you could try alternating with a can of freeze spray for spot cooling the well heated board that might point you to a more specific area.

[tsgunnell]

I don't have the circuit but i would first change the small capacitor inside the heatsink the heat from the heatsink is probably the cause of it's demise

[Guest]

Thanks guys. I managed to get the PSU out of the projector case but still plugged in "enough" to test it. Applying heat to the bank of 680uf caps (Plus one 100uf) on the right gets the board to "startup".

I did look at the cap by the heatsink with suspicion... (another 100uf)

I'm going to order 6 of the caps on the right , plus 2 of the 100 uf caps. Then changed out the 100uf caps 1st (x2 - including the one by the heatsink) and test. If no luck I'll then replace the x6 ones on the right.

[dodgey]

Mr Gunnell - you were 100% correct!

Afrter reading up on how to desolder old circuit boards, then finally prising the bugger off, and badly soldering a new 25v 100uf cap on, whihc I had lying around, she fired up 1st time! YAY!

Thanks all

Soo. for search reference: Infocus Screenplay 5700 no power, clicking, heat, hair dryer - replace the 100uf 16v capacitor in the center of the power supply - the one right next to a heat sink

Thanks again everyone for your input.

[grufman]

i have just performed the same repair on my 5700 and it worked great. I had the same ticking issue also. THANKS ALOT!!!

[gatesnightmare]

Could anyone tell me if the 100uf cap that is right inside the heatsink is listed as c16 and is a 16v

[Guest]

Hey all, I had this same problem with my SP5700 after about 3500hrs, (ca.300hrs on second bulb). The Pj stopped starting up. Power button showed the vague green light flickering instead of strong steadt.
After reading online I tried the hairdryer tip and it worked. I also read that it was most likely the cap marked C16 by the heatsink that needed replacing. (I had not come around to do it.)

To start up the projector, I would blow hot air untill the weak green flickering became a steady strong green light, then the projector would start up. So after a about 5 or 6 times using the hairdryer I noticed when turning the unit off, that the lightbeam would not turn off instantly like normal but instead, a clear/reddish vague light would stay on after I turned it off. I was startled by this and unplugged the power cable.

The next time I was going to turn on the pj using the hairdryer, the power button did not start with a dim green flickering... but came up steady, strong green already, but no reaction from the power switch. It is DEAD..
Now If I leave it plugged in, the projector starts to heat up and feels warm after about an hour plugged in.

So to sum things up, for past few weeks, when plugged in, power button was weak green flickering until hairdryer made it pop to steady green, then pj worked.
Now, when plugged in, the power button is instantly steady strong green but pj does not work. And heats up when plugged in. Any Ideas.

Thanks, Wally, Iceland.
ps. nice pictures dodgey

[ronparchita]

[ronparchita]