Philips FD9944/01S plasma start up issue.

[Dang]

So I've recently been given this as it has a start up issue, initially there is nothing, then it starts to click, just one relay clicking about twice a second, after a while a second relay may start clicking but still no power up. I have used a hair dryer to heat up and localize the issue and it seems it may be a voltage regulator that is at fault(the Tv will start up as per normal once heated up), it's an L7815CV and my confusion starts here. I've measured the output whilst it is clicking and it's just a mess of alternating voltages but once warm, and the Tv is going, it's a steady 93v, now this does not match up with the data sheet I have found or at least from what I can tell: http://pdf1.alldatasheet.com/datashe...S/L7815CV.html. There are also two Rubycon 100uf 50v caps located right next to it with two resistors, one either side, could these be at fault maybe? I suspect it's the VR but I can not be sure, any help on the above will be gratefully appreciated, Andy.

[tom66]

Re: Philips FD9944/01S plasma start up issue.

The regulator is probably floating (not ground referenced) so you need to measure any voltages wrt its ground pin, pin #2 (middle pin), which is also the metal tab.

[Dang]

Re: Philips FD9944/01S plasma start up issue.

Just read up on the idea, probably explains it too, do you think the caps maybe playing a part too?

[Dang]

Re: Philips FD9944/01S plasma start up issue.

This looks like a good replacement: http://pdf1.alldatasheet.com/datashe.../L78S12CV.html, would it work do you think? it will be the 15v version.

[Agent24]

Re: Philips FD9944/01S plasma start up issue.

This looks like a good replacement: http://pdf1.alldatasheet.com/datashe.../L78S12CV.html, would it work do you think? it will be the 15v version.

What exactly are you buying and from where?

[tom66]

Re: Philips FD9944/01S plasma start up issue.

First, test it before needlessly replacing it. It's just a bog standard 7815 regulator. e.g. use LM7815 to replace

[R_J]

Re: Philips FD9944/01S plasma start up issue.

That one cap. near the relays (circled) looks like its skin may be pulled back a bit indecating it got hot, It might be bad if its for the standby voltage that drives the relays.

[Dang]

Re: Philips FD9944/01S plasma start up issue.

It's OK, it's a £1 part and easily replaced so worth a go IMO. It has to be either the VR or the caps as the Tv only switches on normally from cold if those parts are heated up, cost of the parts is £2.16 in total so I'm quite happy to just change the parts and see, if they don't work then it's back to the drawing board.

[Dang]

Re: Philips FD9944/01S plasma start up issue.

That one cap. near the relays (circled) looks like its skin may be pulled back a bit indecating it got hot, It might be bad if its for the standby voltage that drives the relays.

Just had a good look at it and I'd say it's purely a manufacturing defect, seems to test fine, indeed I just checked both caps that I've exemplified using the diode setting on the DMM and both measure differently, could be other things influencing each of them, I don't know, but they measure 738 and 499, I did measure two other paired sets and they were very close to each other so my guess is the low reading could mean a bad cap, it's the nearest one in the photos.

[Agent24]

Re: Philips FD9944/01S plasma start up issue.

I have not heard of any useful capacitor check via DMM diode test function (aside from maybe using it to check for shorts\opens) which are less common.

What you really need to check is ESR and maybe capacitance, especally ESR if heating them makes it work.

If you suspect the regulator, try removing it and setting it up to test on a bench supply or something (if you have one)

Another thing that comes to mind is if the regulator has a bad or badly soldered decoupling capacitor, and heating it makes that work. Without the decoupling capacitor it may be oscillating.

[Dang]

Re: Philips FD9944/01S plasma start up issue.

OK, as a matter of ease I've decided to change the capacitors first, all I've managed to get are 220uf @ 50v, the ones on the board are 100uf @ 50v, are they interchangeable?

[tom66]

Re: Philips FD9944/01S plasma start up issue.

Not in all cases. You should use 100uF unless you have checked the circuit schematic to see if those values would be OK.
CPC sell Panasonic FM/FR/FC capacitors with free delivery.

[Dang]

Re: Philips FD9944/01S plasma start up issue.

So I've now changed the voltage regulator and the two caps pictured above, the Tv will now start on it's own from cold but as before it takes a while, to describe what happens: firstly, there is no standby light, this will then appear within about 30 seconds followed by the first relay starting to click, within about 10 seconds the second relay will start clicking till both stop, you will then hear a faint noise from some caps charging up followed by that same noise again and then the Tv will start, the YSUS can make a slightly louder noise than usual then quietens to a normal steady buzz/humming sound. So it's getting there but still not as it should be, yet again heating the area I described above gets it working very quickly, any ideas are all welcome, thanks, Andy.

[tom66]

Re: Philips FD9944/01S plasma start up issue.

Possibly similar to this one I did?
https://www.badcaps.net/forum/showth...hlight=philips

[Dang]

Re: Philips FD9944/01S plasma start up issue.

Thanks Tom, I viewed this and your Youtube video trying to get ideas and interesting viewing it made, I'm still none the wiser though, can I ask this, why would warming the area I've described effect it in such a positive way even though the components have now been changed?

[tom66]

Re: Philips FD9944/01S plasma start up issue.

It's sometimes difficult to locate a fault, in my case I got it wrong initially, thinking it was the X-caps, it turned out to be some SMD caps quite far away.

[Dang]

Re: Philips FD9944/01S plasma start up issue.

Yep, very much have that idea in mind. I've had a good look and figured it's possibly the connection board, as I said earlier the standby light takes a while to come on and it spurs off the connection board, heating that board can speed things up too, got to laugh, any ideas?

[tom66]

Re: Philips FD9944/01S plasma start up issue.

Narrow it down:

If you have standby voltage, but no standby light = Probably main board.

If you the start up command from main board (PS_ON, VS_ON, VSAGO, VCEGO etc.) but PSU doesn't start = Probably power board.

[Dang]

Re: Philips FD9944/01S plasma start up issue.

Narrow it down:

If you have standby voltage, but no standby light = Probably main board.

If you the start up command from main board (PS_ON, VS_ON, VSAGO, VCEGO etc.) but PSU doesn't start = Probably power board.

I've been doing a little more digging around on this Tv, it seems capacitors 2662, 2663 and 2664 are possible contributors to the fault, two of which I have already replaced so that leaves just 2662 to replace, I shall do that a little later so fingers crossed. There's also talk of a resistor becoming faulty, still to find out what one that is.

[Dang]

Re: Philips FD9944/01S plasma start up issue.

That one cap. near the relays (circled) looks like its skin may be pulled back a bit indecating it got hot, It might be bad if its for the standby voltage that drives the relays.

I think you are right, this cap when heated wasn't reacting, no difference was seen but now that caps 2663 and 2664 have been changed it's reacting straight away so you are most likely right, it needs changing and I shall do that in due course, looks like we may have it fixed, fingers crossed..