Delta DPS-286AP (RDENCA336WJQZ) Troubleshooting

[bznhvx]

D7910 (cathode) = 14.44VDC
D7904 (cathode) = 14.96 VDC
D7919 (cathode) (should be 18v) = 12.18VDC
J7801 (should be 15v) = Cannot locate this Jumper... do you have another component that is on this node?

[R_J]

I made a typo, That should have been, J7081, it is Q7902 emitter. it is the VCC-on voltage that turns on the relay plus various other transistors. It must be supplying some voltage because the relay is switching.
D7910 (cathode) = 14.44VDC
D7904 (cathode) = 14.96 VDC
Thes two votages seem low, they should be at least 20v, I would replace C7918 and C7915 and see if that makes a difference to the voltages.

[bznhvx]

J7081 = 13.56 vdc

[bznhvx]

Originally Posted by R_J

I made a typo, That should have been, J7081, it is Q7902 emitter. it is the VCC-on voltage that turns on the relay plus various other transistors. It must be supplying some voltage because the relay is switching.
D7910 (cathode) = 14.44VDC
D7904 (cathode) = 14.96 VDC
Thes two voltages seem low, they should be at least 20v, I would replace C7918 and C7915 and see if that makes a difference to the voltages.

I just replaced both caps and the voltages stayed the same.

[bznhvx]

It's a shame to throw in the towel on this TV as I'm pretty sure the issue with it is something minor, but without a schematic, it may take more time than it is worth to figure it out. I guess I could part-out the remaining good parts on eBay.

[R_J]

If you have around 12 volts on IC7801 pin 8, that should be high enough for the pFC circuit to operate. But if the ic is damaged and not outputing a drive signal to the two fets, you won't get the boosted voltage. You might also want to check the voltage on pin #3 or mabe easier/safer, check the voltage on J7022, and then on both sides of R7812, this voltage should be around 2~4 voltsdc

If you don't have the equipment (scope etc.) to check the circuit, the only choice you have is to replace the ic. and see if it makes a difference.

[bznhvx]

I have a scope. Will check for gate drive signals. Do the Overvoltage protection circuits shut down the PFC circuits? Just wondering if it would make sense to disable them to see if maybe a problem there could be in play.

[R_J]

Do you have an ISOLATION TRANSFORMER? you will need one if you are working in the primary circuit.

[bznhvx]

Originally Posted by R_J

Do you have an ISOLATION TRANSFORMER? you will need one if you are working in the primary circuit.

Yes, my scope is connected through an isolation transformer. I also have a high voltage probe if needed.

[bznhvx]

IC7801
pin 8 = 13.5vdc
pin 3 = 0.84vdc

J7022 = 4.11vdc
R7812 = 0.83vdc and 4.11vdc

J7022 has a clean looking sinusoidal signal.

[R_J]

Did you check if you have gate drive output from the ic?

[bznhvx]

There are gate drive pulses coming from pin 7 to the pre-driver transistors. This is a very low duty cycle. The pre-drive transistors all pass the static PN junction tests. The output feedback is only at 1V, so the duty cycle should be higher to bring the voltage up.

[R_J]

This ic should be operating at around 70khz. I suspect it is bad.

[bznhvx]

I have checked all the components around the L6562D and don't see any reason for it not to be working, so I am going to order a replacement. The shipping charges are crazy for such a cheap small part, so I want to order a few other spare parts just in case I need them to finish this job. What would you suggest?

[R_J]

Where are you ordering it from?

[bznhvx]

Digikey - they ship USPS so usually lowest cost shipping
Thought I would go ahead and get the parts for the standby 5v since those seem to fail from what I hear. TNY264, some PC123 equivalents, a few of the pre-driver transistors PBSS5140T, and a few diodes since I don't have any surface mount parts in my repair stock.

[R_J]

I get parts shipped from digikey for $8.00, and they ususally arrive next day.

[bznhvx]

Anything else that I may need that you can think of?

[bznhvx]

Index	Quantity	Part Number	Manufacturer Part Number	Description	Customer Reference	Available
1	2	497-8928-1-ND	L6562ATDTR	IC PFC CTRLR TRANSITION 8SO		2
2	10	516-1585-5-ND	HCPL-817-000E	OPTOISOLATOR 5KV TRANSISTOR 4DIP		
3	10	493-5378-1-ND	UPS2A010MDD1TD	CAP ALUM 1UF 20% 100V RADIAL		
4	2	596-1255-5-ND	TNY264PG	IC OFFLINE SWIT OTP OCP HV 8DIP		2
5	5	1727-3906-1-ND	PBSS5140T,215	TRANS PNP 40V 1A SOT23		5
6	10	1727-6174-1-ND	BAS316,135	DIODE GEN PURP 100V 250MA SOD323		
7	10	TZMB20-GS08GICT-ND	TZMB20-GS08	DIODE ZENER 20V 500MW SOD80		
8	2	P6KE120ACT-ND	P6KE120A	TVS DIODE 102V 165V DO204AC		2
9	10	BC3678CT-ND	MBB02070C2208FCT00	RES 2.2 OHM 0.6W 1% AXIAL

[CapLeaker]

Originally Posted by R_J

I get parts shipped from digikey for $8.00, and they ususally arrive next day.

I guess they like you better than me! It takes 3 or 4 days to get here if I am ordering @ Digi-Key . I guess I am living in the sticks!