Dyp-42w2plus bn44-00194a

[capricorn64]

Re: Dyp-42w2plus bn44-00194a

I have checked voltages at VCC_L, VCC_P and VCC_S and I have no voltages well I do but it is reading -0.06V ??

[capricorn64]

Re: Dyp-42w2plus bn44-00194a

Yes it is grounded all the time.

[flocko]

Re: Dyp-42w2plus bn44-00194a

So you need to back track you must be getting voltages to the relays for them to come in at all even for a split second. on ICB802 you have an In /out and ground can you check what voltages you see here when you first ground PS-on (when relay pulls in and drops out)do they change (remember you are on hot ground use the ground pin on IC) Flocko

[budm]

Re: Dyp-42w2plus bn44-00194a

I have checked voltages at VCC_L, VCC_P and VCC_S and I have no voltages well I do but it is reading -0.06V ??

What do you use for ground ref for your meter?
Check the DC Voltage right at the two legs of CB805.

[nogger]

Re: Dyp-42w2plus bn44-00194a

Forget about getting the Vs tract working , you need to get the Va working first & all the other voltages will follow. Check the fuse FXF801, & the 2 FET transistors QX801 & 802 .

Graham

[budm]

Re: Dyp-42w2plus bn44-00194a

Forget about getting the Vs tract working , you need to get the Va working first & all the other voltages will follow. Check the fuse FXF801, & the 2 FET transistors QX801 & 802 .

Graham

If the relays are not on and stay on when PS_ON signal is applied then how are you going to get the AC to feed the bridge BP801S which supplies the power to run the PFC Voltage booster (PAGE 2) which supply PFC Voltage to the fuse FX801S (PAGE 3)? unless you are not looking at the same diagram.

[nogger]

Re: Dyp-42w2plus bn44-00194a

Hi Budm, i do a lot of these PSU's which are basically the same as the BN44-00161A & 162A used in the 42 & 50" models. Key to these is to get the Va tract working (its usually the one that's gone anyway) .

Unless i read the previous posts wrong the relay is coming in then dropping out a few seconds later. If that's the case then the PSU is shutting down due to undervoltage at the output. The VccP & VccS will momentarily come on via QB803 when the Stby volts is connected to PS_On but if there's an undervoltage the protection circuit will cut in & they will drop out. First checks are always the Mosfets QX801 & 802, usually blown open, they often blow the smaller transistors driving TX802S (QX803,4,5,6). They also can blow the ICX801 (MC33067) & recently i had one with shorted turns in the pulse transformer TX802S which gives the same dropping out symptom & is not easy to detect.

If the Mosfets have blown then you are unlikely to get away with just replacing them on their own. Also , a severe Mosfet blow out will take out several components in the PFC circuit including the chip meaning even though the the QX801 & 2 & other parts of the Va tract may be ok it will still drop out because the PFC output will be low.

Luckily , the Vs & Va circuits are almost identical so you can use the Vs one for comparative measurement . First thing i would do now i measure the resistance across the Vs Mosfets & compare against the Va Mosfets, they should be pretty much identical.

Graham

[budm]

Re: Dyp-42w2plus bn44-00194a

OK, I see where the Va, Vs, and the rest of the output Voltages are connected to now.
Thanks for pointing that out.

[nogger]

Re: Dyp-42w2plus bn44-00194a

Just a small correction to my comment above , it should read
"The VccP & VccS will momentarily come on via QB803 when the PS_On is pulled to GND"

[capricorn64]

Re: Dyp-42w2plus bn44-00194a

yes I have it connected to ground all the time, and I am getting a steady 5V at STD_5V ?

[flocko]

Re: Dyp-42w2plus bn44-00194a

Your have 8 posts to check, we would all like to help but we need your feedback when we ask you to check things please tell us what you get, four times you have been asked have you checked the fuses? as Nogger says check for shorted QS801/2 and QX801/2 and DS803/4,RS812/4,and the same DX801/2 ,RX801/4 and both ICS801 Flocko

[Neelix]

Re: Dyp-42w2plus bn44-00194a

Are the relays still switching "on" and then "off" again? At one point in the discussion I got confused and thought you said the relays are staying "on" now and not switching "off" anymore like before

[capricorn64]

Re: Dyp-42w2plus bn44-00194a

I have replied , I explained I was getting -0.06V at the points I have been asked to check and I was getting 5V at STD_5V , and that I have checked the fuses , am I not replying properly as my posts seem to be sending , but I also need to check things before I reply and it would now appear to have a blown QS801 which I need to get a replacement but I am unable to update you until I get a new one and retest the board , I am not ignoring
anyone but I am new to this and trying to learn and understand at the same time !!!!!!!!!!!

[capricorn64]

Re: Dyp-42w2plus bn44-00194a

Hi Neelix the relays , sorry for the confusion , the relays switch on and then switch off straight away when I ground PS_ON .

[flocko]

Re: Dyp-42w2plus bn44-00194a

I would check all the Qs and Qx mosfets out of the board, and also check all smd parts very closely to before replacing or ordering anything Flocko

[nogger]

Re: Dyp-42w2plus bn44-00194a

To be honest a blown QS801 is the least of your worries. The QS801 is in the Vs tract & as i said before you need to get the Va running first. You can fire up one of these boards on the bench without the Vs working, i do it all the time but you must have a good working Va tract. The Va generates all the lower voltages like 5v 12 18v etc etc. Did you do a resistance comparison between the QS & the QX FET's like i suggested earlier ? A blown QS801 probably means a blown QS802 , i certainly wouldn't replace just one of them & the small surface mount resistors & transistors are probably blown as well. I am surprised that you say the fuse FXF801 is ok as i would have expected it to be blown if QS801 is faulty.

In your situation i would do the following, if you are certain QS801 is faulty remove it & QS802 & forget about the Vs side for now, Double check the fuse FXF801 and check for identical resistance reading when reading across the outside pins of both QX801/802 (Gate-Source) Do that & let us know what reading you get. If they aren't more or less identical to each other then you have Va tract problems as well .

Nogger

[flocko]

Re: Dyp-42w2plus bn44-00194a

He will have a Va fault as you say,as he has not fired up the Vs yet so its not QS801 that is bringing in the protection circuit Flocko

[capricorn64]

Re: Dyp-42w2plus bn44-00194a

To be honest a blown QS801 is the least of your worries. The QS801 is in the Vs tract & as i said before you need to get the Va running first. You can fire up one of these boards on the bench without the Vs working, i do it all the time but you must have a good working Va tract. The Va generates all the lower voltages like 5v 12 18v etc etc. Did you do a resistance comparison between the QS & the QX FET's like i suggested earlier ? A blown QS801 probably means a blown QS802 , i certainly wouldn't replace just one of them & the small surface mount resistors & transistors are probably blown as well. I am surprised that you say the fuse FXF801 is ok as i would have expected it to be blown if QS801 is faulty.

In your situation i would do the following, if you are certain QS801 is faulty remove it & QS802 & forget about the Vs side for now, Double check the fuse FXF801 and check for identical resistance reading when reading across the outside pins of both QX801/802 (Gate-Source) Do that & let us know what reading you get. If they aren't more or less identical to each other then you have Va tract problems as well .

Nogger

I have checked all the fuses I can see but this fuse you are talking about FXF801 seems to elude me is it like a normal fuse ?? as I cant seem to see FXF801 on the circuit board, also I have removed just QX801 for the time being and I get no resistance across the 2 outside legs with my meter am I checking this right as I have seen somewhere that I might have to build a little circuit to check the fet ??

[capricorn64]

Re: Dyp-42w2plus bn44-00194a

To be honest a blown QS801 is the least of your worries. The QS801 is in the Vs tract & as i said before you need to get the Va running first. You can fire up one of these boards on the bench without the Vs working, i do it all the time but you must have a good working Va tract. The Va generates all the lower voltages like 5v 12 18v etc etc. Did you do a resistance comparison between the QS & the QX FET's like i suggested earlier ? A blown QS801 probably means a blown QS802 , i certainly wouldn't replace just one of them & the small surface mount resistors & transistors are probably blown as well. I am surprised that you say the fuse FXF801 is ok as i would have expected it to be blown if QS801 is faulty.

In your situation i would do the following, if you are certain QS801 is faulty remove it & QS802 & forget about the Vs side for now, Double check the fuse FXF801 and check for identical resistance reading when reading across the outside pins of both QX801/802 (Gate-Source) Do that & let us know what reading you get. If they aren't more or less identical to each other then you have Va tract problems as well .

Nogger

I have checked QS801 / 802 across the 2 outside legs and I am getting 10.5 ohms on each and when I check the outside legs of QX801 / 802 I get no readings at all.

[nogger]

Re: Dyp-42w2plus bn44-00194a

HI Capricorn64, apologies i got an extra F in that fuse number . It's FX801 & you should find it between the middle 2 heatsinks along with FS801. According to the drawing it should be 4 Amps.

To check a FET lie it down in front of you (face up so you see the numbers on it & pins pointing towards you), pop your meter on diode check setting & put the negative meter probe on the middle pin, keep it there & touch the right hand pin with the positive probe & note the reading. Now keep the negative on the middle pin but touch the left pin (gate) with the positive probe & the reading should drop as you switch the FET on. It's a quick check & you should get similiar results on all the devices.

On the board itself where the FET's are soldered in, find the 3 pins of each FET & with your meter on resistance just measure the resistance across the 2 outside pins of each device (gate-source), you should have equal resistance across each FET. Just do that & let us have the readings.

Nogger