EEVblog #447 - Samsung Plasma Followup.

[AndyC_772]

Although I do not think it is the problem, it is wrong to say switching the input will not affect maldischarge. HDMI and computer may be 60Hz whereas PAL video that the Aussies use is 50Hz. The switch in frame rate affects the priming wave.

OK, fair comment. It should be easy enough to test that theory using an HDMI signal source that can vary its frame rate. Maybe a DVD or Blu-ray player with a selection of different discs - 24p, 50i and 60i should all be straightforward enough.

[tom66]

Remember most older plasmas frame-double 24p into 48Hz (@10 subfields = 480Hz subfield rate) to reduce flickering effects. So either way don't expect much difference between 24Hz and 50Hz.

[Neganur]

It was never there, it is a pad for an extra decoupling capacitor. I would put a guess the Phillips BGA is going intermittent internally when hot, they are rather prone to failing, at least the older satellite decoders here that used a similar chip and a small ADC on the IF converter that ran almost white hot did so. Not helped by them being about the right shape to be pizza boxes, and having about the same amount of cooling.

Nah sorry, a pad where the component never was placed looks differently. This one clearly had the component removed.
>Also, look to the right, some lines share the decoupling with a 47 Ohm resistor, not a second decoupling cap.

[kfitch42]

I would be checking/eliminating.

Power supply associated with analog input channels, check voltages and stability with scope.

This all might be useless given that HDMI is working... but it doesn't look like Dave is following the first few commandments of electronics repair:

1) Thou shalt check voltages
0) Is it plugged in (I think he got that one
-1) Can I trust my tools ( e.g. does my equipment generate good video signals ... which might not be the case for the wonky box that showed the on screen menu)

If the problem is the missing surface mount component someone else noticed, then I suspect rule 1 would have shown something interesting.

[F4CPY]

hello
Found the service manual for PS42s5HX, perhaps it's the same technology for the input board and SAA7119E (page 57)
Time to pull out your best oscilloscope and check the sigs.
http://elektrotanya.com/samsung_ps42s5hx_xex_d72a_sm.pdf/download.html  43Mb PDF
You have to wait a couple of seconds to be allowed to dowload the file (button bellow the image of the file)

Didier

[laree]

I recently discovered your blog and I like it. I wanted to say I have a 2005 vintage Samsung DLP that I have recently replaced because it started to make a loud whining sound like the fan or color wheel was in trouble. (I'd love to send it to you for a teardown, but I'm afraid that would be rather expensive from the US). The input board looks similar to yours except it has two component inputs. At one point, one of the component inputs stopped working. It knew it there was an input (mine seems to mechanically detect when an input is connected and adjust the input accordingly), but would say "No or weak signal." With only one HDMI you really do depend upon having a component input to hook up a set top box and BluRay player; maybe that's the reason yours was disposed of.