sharp lc32d42u power supply - DPS-178APA

[metropical]

last 2 times I had an issue with this supply, it was a 5wt zener in the stand by circuit.
That zener tests good and the 5vt stand by (bu) supply tests good.
Any idea what I could check next?

It's a cheap enough supply on the "pulled" market place, but I might just be inheriting someone elses future problem.

https://flic.kr/s/aHsmKXfqpn

[nomoresonys]

Re: sharp lc32d42u power supply - DPS-178APA

What do you get with test #3 below.

[metropical]

Re: sharp lc32d42u power supply - DPS-178APA

https://flic.kr/s/aHsmKXfqpn

that is a link to snaps of the plugs in case res isn't high enough.

the 2nd pic with 2 plugs; plugs are shown out just so I could get a clear pic. The plugs were in when tested.

bottom plug of 2nd pict.
Pin3 to ground stayed at 0v off and on.
Pin2 stayed at 5v off and on.

the 1st pic is the only other plug on the powerboard.

Thanks for your help, nomoresonys.

[R_J]

Re: sharp lc32d42u power supply - DPS-178APA

The only two pins you checked were on PD pins 2 and 3 ? (pin 3 IS ground)
What about pin #1 which is the PS_ON (power supply ON)?

[metropical]

Re: sharp lc32d42u power supply - DPS-178APA

lemme clarify
top to bottom

p1 - gnd
p2 - bu5v
p3 - pnl power
p4 - gnd
p5 - AC detect
p6 - PS on

I'll go back and check the others.

[budm]

Re: sharp lc32d42u power supply - DPS-178APA

You count the PD connector pin wrong:
Pin 1 = PS-ON
Pin 2 = AC_DET
Pin 3 = GND
Pin 4 = PNL POWER
Pin 5 = BU 5V
Pin 6 = GND

[metropical]

Re: sharp lc32d42u power supply - DPS-178APA

OFF ON

Pin 1 = PS-ON - 3v 3v
Pin 2 = AC_DET - 3v 3v
Pin 3 = GND -
Pin 4 = PNL POWER - 0v 0v
Pin 5 = BU 5V - 5v 5v
Pin 6 = GND-

In other words, voltages didn't change off to on.

[metropical]

Re: sharp lc32d42u power supply - DPS-178APA

I forgot to mention that the front "stand by" LED has been cycling since the failure.
~.5 sec off/~5 sec on.

The service book I have shows a "power board" on p 10-39 to 10-42.
PDF page 100-103.
On page 102 there is a representation of the plug and voltages of which I've been testing.

1 - PS_ON 2.8v - I get 3.025
2 - AC_DET 3.2v - 3.08
3 - G
4 - PNL_POW 3.3v - 0v
5 - BU5V 5v - 5v
6 - G

So it appears P4 is missing it's voltage.

Though I don't think this is an exact representation of the components on the actual pcb I have.

[metropical]

Re: sharp lc32d42u power supply - DPS-178APA

I think that P4 PNL_POW is a return voltage, not a source from the PS.
But what am I looking for and where.?
.
My time with board level stuff was on recording studio gear 30 years ago.
Not so familiar with this.

[will62]

Re: sharp lc32d42u power supply - DPS-178APA

The pnl_pow voltage comes from IC2007 (AND gate). It requires ~3v from both the cpu and mcu to send the pnl_pow voltage. See pages 72 and 102 in the SM.

[R_J]

Re: sharp lc32d42u power supply - DPS-178APA

I think that P4 PNL_POW is a return voltage, not a source from the PS.
But what am I looking for and where.?
.
My time with board level stuff was on recording studio gear 30 years ago.
Not so familiar with this.

PNL_POW is the "control voltage for the panel 5v" All it does is switch the PNL5V ON or OFF that's it, nothing else
A high or low logic (3.3v - 0v) on the PNL_POW pin turns Q7907 on or off which tells Q7905 to connect the BU5V to the PNL5V
You have confirmed that PNL_POW is changing from 3.3v to 0v, all you need to do is check plug PE pins 3or4 (or use J7915) PNL5V and see if it changes from 0 to 5v when PNL_POW changes.

[metropical]

Re: sharp lc32d42u power supply - DPS-178APA

I know this is odd, but I think I may have a different board. I don't see IC2007 on the actual board, despite what the SM shows.
Unless it under this heat sink, pic attached.
.
But still, when I swapped the PS, the tv worked.
So I don't understand why I'd be looking outside the PS.

[budm]

Re: sharp lc32d42u power supply - DPS-178APA

So are you saying that with old power supply board the PNL_POW of PD connector shows 0V, but with new power supply it shows 3.3V?

[metropical]

Re: sharp lc32d42u power supply - DPS-178APA

sorry, my post is poorly formatted.
P4 is 0v on the bad PS.
3.3v is what is stated in the SM.
.
I swapped the PS with another one of these TVs we had that failed.
So I now have the failed supply.
When I put the known good PS in the bum TV, it lit up NP.
.

That post was suppose to look columnar, but alas...

[budm]

Re: sharp lc32d42u power supply - DPS-178APA

sorry, my post is poorly formatted.
P4 is 0v on the bad PS.
3.3v is what is stated in the SM.
.
I swapped the PS with another one of these TVs we had that failed.
So I now have the failed supply.
When I put the known good PS in the bum TV, it lit up NP.
.

That post was suppose to look columnar, but alas...

I do not understand, you said TV works with new board, so PNL_POW of PD connector shows 3.3V then when using the new power supply board?

[metropical]

Re: sharp lc32d42u power supply - DPS-178APA

I assume so. But that TV isn't here.
What I'm saying is the other TV failed. I put the other PS in it and it works fine.
But that TV is in a different location. I now have it's failed supply.
It is 0v on P4.

[R_J]

Re: sharp lc32d42u power supply - DPS-178APA

I assume so. But that TV isn't here.
What I'm saying is the other TV failed. I put the other PS in it and it works fine.
But that TV is in a different location. I now have it's failed supply.
It is 0v on P4.

What is P4? I see plug PE and plug PD

[metropical]

Re: sharp lc32d42u power supply - DPS-178APA

yes, Pin 4 on plug PD. aka PNL_POW 3.3v. I have 0v on this supply.

[R_J]

Re: sharp lc32d42u power supply - DPS-178APA

yes, Pin 4 on plug PD. aka PNL_POW 3.3v. I have 0v on this supply.

That is because it is NOT A SUPPLY, please re-read post 11

Here: Red is the BU5V volts, Blue is the panel power 5 VOLT OUTPUT, Yellow is the PNL_POW Control line.

[budm]

Re: sharp lc32d42u power supply - DPS-178APA

that is because it is not a supply, please re-read post 11

+10