Hyundai HQL320WR/LT32AW000 - Dead power supply

[ceconomon]

Found this Hyundia set disposed improperly at a paper recycling center and thought I'd get some entertainment out of it.

The set showed no signs of life when trying to turn it on. I tore it apart and determined there was no output current on the power board. There is a brownish spot on the bottom of the board. The two resistors (R6) had a bad solder joint that I reflowed. I was also able to confirm the fuse is blown.

I'm going to replace the fuse and re-cap the board. Does anyone have any other parts they would recommend replacing?

[budm]

Re: Hyundai HQL320WR/LT32AW000 - Dead power supply

'I'm going to replace the fuse and re-cap the board. Does anyone have any other parts they would recommend replacing?' I would look for shorted components first, that way you do not waste good fuses.

[CapLeaker]

Re: Hyundai HQL320WR/LT32AW000 - Dead power supply

really? fixing a 10 year old 32" TV? Oh well... lets keep things out of the landfill if we can. If the fuse went, a resistor got really hot, there is a very good chance that something drew a lot of current and blew. So look for shorts on diodes and Mosfets.

[ceconomon]

Re: Hyundai HQL320WR/LT32AW000 - Dead power supply

CapLeaker: Why am I looking at a 10 year old TV? To expand my knowledge on fixing things.

I was able to replace the fuse and caps on this power supply. The 14V side of the board is working, but the 24V side is still dead.

I learned how to use the diode testing function on my VOM. Had no clue it had that capability nor had I ever tested a diode before.

I checked the D2 (UF5407) diode and it has a reading of .409. This is on the low side from what I've found. I'll have to source a replacement and check things from there.

[CapLeaker]

Re: Hyundai HQL320WR/LT32AW000 - Dead power supply

Knowledge is always good and keeping things out of the landfill is even better.
D2 should be fine. How much voltage are you getting on the big filter cap on the primary side, when the PSU is on? Be careful there, in the primary you are connected to the mains and there are very high voltages. If you are getting something >360VDC on the filter cap, your PFC is working fine. Then proceed to the 24v on the secondary and check the rectifier diode(s) there.
Also check the caps on the 24V section. They look like they got hot and the plastic shrank (the top ones on the right). When a cap get's hot like that, it means the ESR is waay up and needs to be replaced.

[ceconomon]

Re: Hyundai HQL320WR/LT32AW000 - Dead power supply

The big filter cap is reading 165V across the pins and the rectifier diode (top right corner) reads .307 on both sides. The caps on the top right were replaced a few weeks ago.

[budm]

Re: Hyundai HQL320WR/LT32AW000 - Dead power supply

Since you are getting the 14VDC (odd Voltage level) on the output side that means the main DC in the primary side is working.
There are labels for each pins of those two white connactors, what are the names of each pin and the DCV readings (when TV is OFF and when TV's Power switch is activated) of each pin when all the boards are connected together?

[ceconomon]

Re: Hyundai HQL320WR/LT32AW000 - Dead power supply

I did note there is clicking noise on the power supply that is timed with the flicker of the standby light. This explains why I was seeing some fluctuation in the voltage on the 14V side. It remains steady after things have warmed up.

24V side
PINS 1-4=0v
PINS 5-8=Ground
B=0v
A=0V

14V Side
A=0V
B=0V
PINS 3-4=Ground
PINS 5-6=14V
S=1.14V

[budm]

Re: Hyundai HQL320WR/LT32AW000 - Dead power supply

There are 3 small electrolytics caps next to D3, D4, and R12 so try heating them with hair dryer for a few minutes the plug the TV into the outlet to see if the 14V will become steady.

[CapLeaker]

Re: Hyundai HQL320WR/LT32AW000 - Dead power supply

There are 3 small electrolytics caps next to D3, D4, and R12 so try heating them with hair dryer for a few minutes the plug the TV into the outlet to see if the 14V will become steady.

x 2 and D8 isn't installed on your last pic either.

[budm]

Re: Hyundai HQL320WR/LT32AW000 - Dead power supply

x 2 and D8 isn't installed on your last pic either.

I wonder why too as to why D8 is removed.

[Clutchbox]

Re: Hyundai HQL320WR/LT32AW000 - Dead power supply

The caps on the top right were replaced a few weeks ago.

And what caps have you chosen? Nichicon VR-series? (85C Gen.Purpose)

[CapLeaker]

Re: Hyundai HQL320WR/LT32AW000 - Dead power supply

And what caps have you chosen? Nichicon VR-series? (85C Gen.Purpose)

well... that's another discussion, but at this point lets get that thing up and running first. I can't see what they exactly are, but I do see a 105 and Nichicon.