Sharp LC-60SQ15U TV DPS-167CP - No power
 

Hi everyone!

This Sharp LC-60SQ15U TV was hit by a near lightning strike. The Delta DPS-167CP power supply has no power output at all, thus no power to the screen, no LEDs, etc. My first order of business is to try to figure out why it doesn't have any 5V constant output.

The fuse at F7001 is fine. The large rectifier at BD7001 has 160.3VDC measured on the far leads. All the capacitors look visually OK and test OK with an in circuit ESR tester. A quick check of the resistors doesn't show any that are open circuit, but I haven't checked their exact measurements yet. I'm working on tracing where the 5V constant comes from, but thought I'd start a post to see if anyone has experience with this power supply. Any common faults or places to start looking/testing?

Many thanks, in advance.

I've attached a couple images of the power supply. Also, ShopJimmy has some good photos: http://www.shopjimmy.com/sharp-runtk...-led-board.htm

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

Check fusible resistor R7900 (2.2 Ohms) to see if it is open.
IC7903 is the STBY SMPS IC which drives the power transformer T7901, D7950 is the rectifier diode on the Cold side.
You should run the power supply board by itself to see if you do have STBY Voltage or not.

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

Thanks for the quick reply! R7900 is measuring 2.4 Ohms.

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

Try running the power uspply board by itself without other board connected in case the main board has shorted circuit and loaded down the STBY power supply.

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

So right now you are not getting DCV on any pins of the PD connector, verify?

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

Correct, no DCV on any any output pin. Sorry, I should have mentioned that I tested with the other boards disconnected last night. Just tested again to be certain. No output whatsoever even without load on the power supply.

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

Need to get the P/N of IC7903 so you can check and see if it has VCC to run the IC or not.
You still need to check D7950 tof ind out if it is shorted or not.

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

IC7903 looks to be an A6069H. I found this data sheet: http://media.digikey.com/pdf/Data%20...000_Series.pdf

It's getting 161V between pins 8 and 3. I'm only measuring .031V between pins 5 and 3.

D7950 is testing strangely. Forward voltage drop is .315V, but when I test the reverse voltage, it hunts around in between -1.5V and -1.9V before it finally settles on 0. [Edit - tested OK once removed from the circuit]

I'm pretty sure D7904 is shorted with .012V drop in both directions. [Edit - tested OK once removed from the circuit]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

OK, after looking at the board traces, the D7904 (it is the rectifier diode that convert AC from the AUX winding of the STBY transformer to provide the running VCC Voltage one the IC is in running mode) should lift up one leg off the board and test it again, if it is not tested bad then more likely the IC VCC pin 5 is shorted out or the filter cap C7906, or Zener D7910 is shorted (You can lift one leg off the board to see if the shorts will go away).
The SMPS IC is STR-A6000 series.

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

Removed and tested D7904 and D7950. They tested fine once removed from the circuit. I think I'm leaning towards the IC being shorted. I'll have to save the C7906 and D7910 test for tomorrow. I have my 4 year old watching, but his patience is about up. Thanks so much for your help! It looks like I'll have to get an order together soon.

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

Any idea what the specs are on C7906 (no markings) and D7910 (has a 202 on it)? I get a little nervous working with SMD stuff and not having a backup. Remember the good old days when everything had a schematic? :)

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

Do not worry about the value of the cap or the diode yet, need to find out why you are getting bad reading on D7904 first, so do what I suggest first.

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

Will do, got delayed fixing my wife's car, but I'll post back soon. Thanks again for all the help!

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

Hi egoh,
I have the exact same board with the exact same symptoms (160 VDC at BD7001 output and no voltage at any PD connector pin). Did you ever figure it out?

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

Have you done above tests suggested by budm?

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

Yes, and I did find R7900 open. I'm a little confused by its color code. It is Red-Red-Gold-Gold-Silver. If I ignore the silver band, it matches the above post from budm as a 2.2 ohm 5%. Any idea what the last silver band would be? For a standard 5 band, the 3rd can't be gold.
Thanks.

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

You will need to look for shorts before replacing resistor. May have a bad IC7903 or diode

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

Sorry, I got busy with car and house repairs. I ended up replacing the board and haven't circled back to diagnose the original failed board.

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

Update: I figured the shorted diode was the culprit so after replacing blown R7900 and shorted D7950, I powered up the board and R7900 immediately blew, but D7950 was still good. I then replaced IC7903 and R7900 and the board powered up normally! The TV works perfectly!

Thank you everyone for all the help!

Re: Sharp LC-60SQ15U TV DPS-167CP - No power
 

What was the specs on the D7950 diode? Mine blew and the text on it is unreadable.