Samsung PS-42Q7HD clicking, blue flashing LED, no power

[tom66]

Picked this one up on Friday but haven't had enough time to look at it - the relays click inside, the power LED flashes but there's no picture. I haven't checked sound yet.

It may just be some solder joints if I'm super lucky but it could also be shorted FETs. Some report bad caps, others report a burnt 330k resistor... it could be anything. More fun!

My second Samsung plasma. First one was just a dead X-sus and it was only 6 months old! This one is a little older, but HD Ready with Freeview.

Opening it up in a few hours...

[tom66]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

Okay, got it in the shed. Big beast!

Immediately checked the PSU for cold joints. Very badly cold jointed in places. However, reflowing these didn't solve the issue.

Vs is dead; Va is okay (65V.)

I immediately noticed (after reflowing about 30 joints!) that there was a bad cap on the Y-sustain, 50V 100uF. Bulging nicely.

Then, I unplugged the Y-sus; Vs was still dead. Unplugged the X-sus, and Vs rose to 200V, rated 198V. So, the problem is on the X-sus. Checked the X-sus, it's completely shorted to ground on the Vs node.

The set still doesn't power up properly without the X-sus but I do get a limited sustain waveform out of the Y-sus (only about 20Vp-p though; not enough for PDP discharge.) I suspect the bad cap is causing issues, as the ripple across it was... 8Vp-p!! OR, it will not power up without the X-sus due to a protection circuit.

Found a new X-sus on ebay for £17.80 shipped, so I'm going for that. I'll replace the cap too, and reflow more joints, then see how it goes!

[ben7]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

Okay, got it in the shed. Big beast!

Immediately checked the PSU for cold joints. Very badly cold jointed in places. However, reflowing these didn't solve the issue.

Vs is dead; Va is okay (65V.)

I immediately noticed (after reflowing about 30 joints!) that there was a bad cap on the Y-sustain, 50V 100uF. Bulging nicely.

Then, I unplugged the Y-sus; Vs was still dead. Unplugged the X-sus, and Vs rose to 200V, rated 198V. So, the problem is on the X-sus. Checked the X-sus, it's completely shorted to ground on the Vs node.

The set still doesn't power up properly without the X-sus but I do get a limited sustain waveform out of the Y-sus (only about 20Vp-p though; not enough for PDP discharge.) I suspect the bad cap is causing issues, as the ripple across it was... 8Vp-p!! OR, it will not power up without the X-sus due to a protection circuit.

Found a new X-sus on ebay for £17.80 shipped, so I'm going for that. I'll replace the cap too, and reflow more joints, then see how it goes!

good luck! You should recap the PSU, they (usually) are full of crapxons. Ours still has the crapxons in it too - I didnt even get a chance to replace them cuz everyone else was so desprate to have a working TV

[tom66]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

good luck! You should recap the PSU, they (usually) are full of crapxons. Ours still has the crapxons in it too - I didnt even get a chance to replace them cuz everyone else was so desprate to have a working TV

I might replace them, but there are nearly 20 on the power supply. So it's going to be very difficult and expensive.

[tom66]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

Well, it's fixed.

First I replaced the cap on the Y-sus then I got a nice, clean waveform out of Y-sus. As expected I got a dim picture with the X-sus removed. So I replaced X-sus, and TV works great now.

[JonathanAnon]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

Hey Tom,

I have one of these to fix.. Did you ever find the schematic or service manual for this TV..

tks.

[tom66]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

No schematics for Samsung.
Service guides:
http://www.tgohome.com/ServiceManual...&Search=Submit

[JonathanAnon]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

Thanks for that tom.. I have the relay clicking problem, but I've replaced all the bad caps, chips and fuses... (the ones recommended in the repair kit for the relay clicking issue).. but it's still clicking.. I've disconnected the boards and the relay click stops when I disconnect the video board..

Obviously this is because it doesnt receive the PSON, but I've tried the same trick you showed me last time with the other samsung(jumper 3 / 4 on logic board, disconnect video board, and jumper PSON on PSU).. but it doesnt seem to work for this model.. I hear it clicking on with the jumper on but the VA and VA voltages dont turn on... Any ideas? tks

[tom66]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

Unplugged Y-main and X-main? BOTH of them?

[JonathanAnon]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

- disconnect the main connection to the Y SUS which chains over to the X SUS and the relay clicking still happens
- disconnect the logic board and the relay clicking happens..
- disconnect the video board (with a resistor across the PSON-GND to turn it on) and the relay clicking doesnt happen. The standby voltages and voltages to the video board are all good, but the Va and Vs are not on..

From what it says in the service manual,

Problem: The SMPS relay is repeatedly turned on and off.

In general, the SMPS relay repeatedly turns on and off by the protection function due to a defect on a board connected to the SMPS.
- Disconnect all cables from the SMPS, operate the SMPS alone and check if the SMPS works properly and if
each voltage output is correct.
- If the symptom continues even when SMPS is operated alone, replace the SMPS.
- If the symptom is not observed when operating the SMPS alone, find any defective assemblies by connecting
the cables one by one.

At this point it would be very helpful for me to work out if the video board is causing the shutdown. A similar video test to the one you showed me for the other samsung plasma would be very helpful, but I'm not sure that's available with this model..

[tom66]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

Check the PSON/VSON while plugged into the main board.

[JonathanAnon]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

Okay, below is a video of what happens when the video board is connected and I have the multimeter red to PSON and black to RTN (ground).

http://www.youtube.com/watch?v=bQxqh8gxXoI

The voltage goes to 3.2v then seems to go back to 0.47v when the relay clicks off.. This repeats..

I also put the red probes probe to VSON (on the logic board) and the black to RTN. It goes to 200mV when switched on, then goes immediately to 0mV when the relay clicks off.

[tom66]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

OK, can you try the resistor trick with both VSON and PSON?
Have you tried... https://www.badcaps.net/forum/showpo...61&postcount=2 ?

[JonathanAnon]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

OK, can you try the resistor trick with both VSON and PSON? Have you tried... https://www.badcaps.net/forum/showpo...61&postcount=2 ?

I did that test in the link above, from what I remember it clicked on but there was no display at all. (I actually carried out this test for practice when I got the new Y-Sus for the other Samsung TV, so I'm sure I was doing it right). I just assumed that the same test was no available on this model.

I was contemplating jumping the VSON, but I've never done it before so I was a bit reluctant... I'll try it.

[JonathanAnon]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

http://www.youtube.com/watch?v=wyyOC9TFiOM

Samsung Self Test:

Above is a video of me carrying out the test described in that URL you sent me. 3-4 on the logic board jumpered, all cables from the main board disconnected, and PSon jumpered to ground.. Both relays click on AND stay on but there is no Va, no VS and obviously no image on the screen..

VSon and PSon test:

When I plug in the PSU board alone, then jumper PSON to ground and VSON to ground, it is exactly the same result.. Both relays click on AND stay on, but there is no voltage on Vs and Va...

I think maybe I just didnt repair the PSU properly, and there must be some other components that were killed when it blew..

[tom66]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

Since you have applied the jumpers, it definitely sounds like PSU to me. With regards to the fault, a common issue is cold solder joints followed by blown fets. When the fets blow sometimes they take out a fuse.

[JonathanAnon]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

http://www.ohmsupplies.co.uk/epages/...roducts/KIT156

I spotted this repair kit this for the fault... Three of the components from this list were blown on my TV (I replaced with exact matches) and I tested all of the rest of the components out of circuit which were all fine. But I will work back along the line, starting with the voltage on the main 450V filter caps..... say goodbye to another ten hours

[tom66]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

Ahah! Is this your power board?
http://www.tgohome.com/ServiceManual...&Search=Submit

May help you to have a schematic... I just had to find the BN44 number...

[JonathanAnon]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

Nah, that's not the one Tom...

BN96-03743A is the PSU in my one.. I've spent a couple of hours searching for it.. but came up with nothing.

It looks like this

[tom66]

Re: Samsung PS-42Q7HD clicking, blue flashing LED, no power

BN96 is the assy num, but the blank board is BN44. But it doesn't match. Close, but slightly different. I'll have another look around.