Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

[calimark]

Hello,

I've signed up to hopefully get some assistance beyond where I am stuck.
Unfortunately I have been unable to find a PSU schematic for this unit.

Symptoms:
2 Power Lights flashes with 1 Opc Flash.
Per SVC manual, that is DET_15V missing.

Behaviour noted:
If TV has been sitting off for a while it will turn on no problem.
If TV is turned on(even for 10seconds) then turned off and back on AFTER the relay shuts off- it will do the light flash sequence.

When TV is on, it works perfectly. If you power off and power on BEFORE the relay shuts down it works every time.

Voltage measures:
AC DET is ok
5V stdby is ok
PSU_ON - jumps high then drops low when error condition is seen.
PSU_ON- stays high when no error condition present.
During error condition, there is no 15V.

Off Unit troubleshooting:
Removed PSU from TV and jumped PSU_ON to stdby via 2.2K resistor.
There is no power switch so you just plug in the 120V main.
When that is done, the relay clicks and all voltages are measured as expected.
Disconnect the PSU_ON, relay clicks off one second later, and the 15V SLOWLY drains down.
If you disconnect the PSU_ON and reconnect it BEFORE the 15V is drained the error condition presents it self.


During error condition(off the unit), there really is only stdby, ac_on present.
The 12V,15V & 24V are all missing, which has me thinking what's common to all of them. Without a schematic I'm sort of stuck.

I've measured most of the diodes without seeing any issue. One was weird but measured fine off the board.

[newtothis]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

Can you give us a pic of entire board and one of chasses layout please

[calimark]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

Here you go.
Since I Have it mounted I took top down photos.

PSU right side, some board in middle, left side has AV panel etc.
PSU_ON comes from the board with AV panel on it

[calimark]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

bump for some inputs

[budm]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

So when you forced on the power supply board.
The missing 12V, do you mean the PNL12V? It requires to have PNL-PWR command signal ti turn on this 12V
The 15V, do mean the UNR14.3V?

Shopjimmy does not have pictures for the bottom side of the board so you need to take really good clear pictures of the bottom side of the board, they must be clear enough to trace the connections.

[calimark]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

So when you forced on the power supply board.
The missing 12V, do you mean the PNL12V? It requires to have PNL-PWR command signal ti turn on this 12V
The 15V, do mean the UNR14.3V?

Shopjimmy does not have pictures for the bottom side of the board so you need to take really good clear pictures of the bottom side of the board, they must be clear enough to trace the connections.

Ok I did not know that abt the 12V. So I'll throw that out from the loop for now. Yes for 15V I mean UNR14.3V

I have some updated photos in this post about as good as I could get at the moment.

Unfortunately, I took the board out to measure a few V back to D7140 and couldn't recreate the issue. I then placed the board back in the TV and could not replicate it. The only thing that comes to mind was a full overnight cool off at 75-76F. I will run it and try to get a measure back to that component. Its accessible from the top so it could be measured in the unit.

[danygohe]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

do you know the number for the ic ic7905 i have the same board but that ic is missing

[calimark]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

do you know the number for the ic ic7905 i have the same board but that ic is missing

Actually I'm not so sure its the same board. I do not have 7905...but have 7605.
PN DLA001D

[calimark]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

Hello,

After several months of working, this set is kaput.
Now the symptoms point to PNL12V not coming on.
I disconnected tconn and I can see there is backlight.
I can hear audio, but I dont see anything.

I removed the PSU and I have jumped the PSU ON and PNL PWR to trigger 'ON'.

There is definitely no PNL 12V. I managed to trace it back to a mosfet 40P03GI
I checked that guy and I see 12V on the Gate to GND.
I see 12V at Source to GND
Drain to GND has 0V.
On the Drain I noticed a choke, which ties that pin back to the source through a diode.

G>D junction is 12V
S>D junction is also 12V

Can anyone guide further on what else to check here, and comment if anything is incorrect so far.
Vgs shows as 30V on the data sheet so I'm thinking this thing should be on.

[freakaftr8]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

Well doing in ohms test between the center pin to outside pins do you see a short?

[fzabkar]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

AP40P03GI, APEC, P-channel Enhancement Mode MOSFET, TO220F, -30V, -30A:


The G-S voltage is 0V so the MOSFET should be off, ie the D-S voltage should be 12V. So nothing wrong there.

[calimark]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

AP40P03GI, APEC, P-channel Enhancement Mode MOSFET, TO220F, -30V, -30A:


The G-S voltage is 0V so the MOSFET should be off, ie the D-S voltage should be 12V. So nothing wrong there.

Ok thanks for that pointer. I didnt realize G-S needed to have a pd. I thought it was G-GND that needed some voltage.

So with that info I was able to trace down the issue to one diode.
I replace it with a generic diode I had on hand and it works.
The 'bad diode' has a 0.7v drop off the board but when on the board it didnt conduct anything- weird for me.

I'm also attaching the partial shcematic that I managed to trace out. It might have an error but it gave me enough of a picture to find the issue.
D7123 was the problem ~5V on one side, nothing on the other.

Attached a photo of the temporary patch. Should I just get any surface mount diode that fit the foot print?

Now the tv comes on & stays on(prior I had to jump start with channel down,volume up and it would only stay on a few seconds)
12V is good, audio works. ALL V are good, backlight still good, BUT STILL NO PICTURE.

I started looking around at the ribbon connectors and found 2 with some damage to the gold contacts. ( I had attempted reseating as a quick first step). I belive they may have been damaged during that process.
Part number on them is H089WT.

Does anyone have any idea what IC7501 is? It's bulging but I cant get a read of any marking on it.

[calimark]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

After playing with the cables I now have a picture. I am not fully sold on the cable longevity so I will try to get new cables!

[freakaftr8]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

That would definitely cause the no picture. Sometimes what I've done was to cut the cable back and carefully try to clean the white laminate off of the ribbon and create new connections

[calimark]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

That would definitely cause the no picture. Sometimes what I've done was to cut the cable back and carefully try to clean the white laminate off of the ribbon and create new connections

Thanks for that tip.
I'm definitely going to need ribbons. One half of the screen is darker than the other, so its not perfect but at least confidence is high that good ribbons will have me back to normal.

Do you have any idea about that bulging IC79xx I mentioned?
Should I even bother to get a SMT diode? Or leave the patch in place?

[mu34tant]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

did you ever fix this?

[calimark]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

did you ever fix this?

Which aspect are you asking about?
Everything is detailed above.

Only the ribbons, I have not sorted out yet. Still looking for a pair at cheap price.

[mu34tant]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

yep

[calimark]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

All good here now. Grabbed a pair of ribbon with matching 80 pins off ebay and everything is normal now.

[thoma]

Re: Sharp LC-C6077UN (DPS-343AP) PSU issue DET_15V

DPS-343AP is there a schematic?
regards thoma!