17IPS20 No Led Voltage Solved With Video :)

[ReeceyBurger123]

Hi all I know theres alot of issues with these supplies and no backlight, today the symptoms of the issue with this one were the following:

No backlight
0v on Led output
Q502 and D504-Led output boost devices not shorted
0v on D303-D314 which are 6 diodes in parallel for Led output meaning Q301 transistor for Led output is not turning on enough or at all
Found only 330v across main caps meaning Pfc mosfet Q100 not turning on
Pfc controller U101 starts then shuts down Vcc drive voltage meaning issue is in the primary side

Things to check:

Q301 for S/C
Q101 for S/C note both these can blow and if their resistors fail open quick enough the mains fuse will not blow and Psu likely will start with no backlight
D506 for leakage current, this diode does not normally fail S/C but leaky acorss the cathode to anode so check that

What I found:

U300 check if its sending Vcc now I found it did but then shut down too meaning issue with either U101 or U300 or related parts
Checked U101 found low resistance across pins 1 and 3
Checked C127 (near U101) 50 ohms across it meaning theres a short acorss that cap, removed and checked however cap is fine out of circuit
Then checked C525 (under Q301) which is in parallel with C127 and both U101 and U300
C525 had lower resistance across it
Removed C525 and its shorted
Checked controllers again and low resistance gone
Replaced C525 which I believe is a 1uf 50v multilayer ceramic cap-MLCC stole one off a scrap IPS20 which is not worth fixing and replaced resistance still good

Put the Psu back into the Tv and the set now works. Hopefully help someone out, remember to check that cap if your Led section is totally dead with no output

Video coming tomorrow or Tuesday.

[ReeceyBurger123]

Re: 17IPS20 No Led Voltage Solved With Video

I also forgot too add, the motherboard (17MB95) was also totally dead the standby Led would flash then die flash then die, swapping the Mb for a similar one sorted the issue. So I wonder if the Psu cap shorted killed the Mb at the same time ? Or the set got hit by a surge ?

[comptek]

Re: 17IPS20 No Led Voltage Solved With Video

another great fix

[ReeceyBurger123]

Re: 17IPS20 No Led Voltage Solved With Video

Cheers buddy, got that board yet as well ? Also yes saved me £ again

[ReeceyBurger123]

Re: 17IPS20 No Led Voltage Solved With Video

Link to video chaps, hopefully help someone:

https://m.youtube.com/watch?v=uPI1QBE0CxI

[diif]

Re: 17IPS20 No Led Voltage Solved With Video

Nice work as always mate.

[ReeceyBurger123]

Re: 17IPS20 No Led Voltage Solved With Video

Nice work as always mate.

Cheers matey, keep these Vestels out the land fill

[diif]

Re: 17IPS20 No Led Voltage Solved With Video

Yep, working on a 17PW20 at present.

[ReeceyBurger123]

Re: 17IPS20 No Led Voltage Solved With Video

Cool cool, whats the issue mate ?

[diif]

Re: 17IPS20 No Led Voltage Solved With Video

Cool cool, whats the issue mate ?

TV powers on for a second giving the blue screen before going back to standby.
I disconnect the inverter and the TV stays on. No shorts on the inverter or the spare I have, the two poly caps have been changed and other electrolytics checked.

[ReeceyBurger123]

Re: 17IPS20 No Led Voltage Solved With Video

TV powers on for a second giving the blue screen before going back to standby.
I disconnect the inverter and the TV stays on. No shorts on the inverter or the spare I have, the two poly caps have been changed and other electrolytics checked.

Hmm seems like the Pfc is low to me, this can cause 24v shut down which crashes the set. Whats the pfc running at ?

[Th3_uN1Qu3]

Re: 17IPS20 No Led Voltage Solved With Video

That is pretty informative and i am sure will come in handy to newbies. Thank you!

[ReeceyBurger123]

Re: 17IPS20 No Led Voltage Solved With Video

That is pretty informative and i am sure will come in handy to newbies. Thank you!

Cheers mate

[dick_barton]

Re: 17IPS20 No Led Voltage Solved With Video

Just to add an addition comment when repairing this power supply.

Thanks to ReeceyBurger123's video on this supply I found C525 (10uf 50V) was faulty and reading 90 ohms out of circuit.

The minimum working voltage for U101 (FAN7529 is 14.5V) and VCC on the chip measured only 10.5V so was still to low.

On checking through the circuit I finally found a collector - base short circuit on Q216 (BC327).

Replaced and PFC voltage now up and running.

[ReeceyBurger123]

Re: 17IPS20 No Led Voltage Solved With Video

Just to add an addition comment when repairing this power supply.

Thanks to ReeceyBurger123's video on this supply I found C525 (10uf 50V) was faulty and reading 90 ohms out of circuit.

The minimum working voltage for U101 (FAN7529 is 14.5V) and VCC on the chip measured only 10.5V so was still to low.

On checking through the circuit I finally found a collector - base short circuit on Q216 (BC327).

Replaced and PFC voltage now up and running.

Nice work matey, as I said before that device can fail too. Unser what causes these just random issues on Vestels though just crappy designs I guess.

[Wroxall Tony]

Re: 17IPS20 No Led Voltage Solved With Video

Hello guys, this is my first post so please don't be cross if I'm asking this in the wrong place or the wrong way! I'm stuck with a duff 17IPS20 for a Hitachi 42HXT12U, with a board no. 23145840. I can't find a replacement board, but there are plenty of 23145828 available for this model TV. Does anyone know if this will work as a replacement for 23145840, please?

[ReeceyBurger123]

Re: 17IPS20 No Led Voltage Solved With Video

Hello guys, this is my first post so please don't be cross if I'm asking this in the wrong place or the wrong way! I'm stuck with a duff 17IPS20 for a Hitachi 42HXT12U, with a board no. 23145840. I can't find a replacement board, but there are plenty of 23145828 available for this model TV. Does anyone know if this will work as a replacement for 23145840, please?

Welcome, also what is the issue with your board for a start ? Also you can use any IPS20 that works for a 42" size screen dont bother watching all the number BS up dont let it confuse you. Got an image of the board yours uses and I will find one as the only thing different they do for the 42" sets is sometimes use a different Led connector ?

[Wroxall Tony]

Re: 17IPS20 No Led Voltage Solved With Video

Thanks for such a quick reply. There's zero voltage on the output to the LEDs, and rather than spend ages trying to identify the failed component I thought I'd just slap in a new board. I've looked at images of the 23145828 board and it looks identical to mine, so with your very helpful advice I'll go for that. I can always change the LED connector. If it doesn't work it's only a few quid and worth it for the experience! Thanks again!

[ReeceyBurger123]

Re: 17IPS20 No Led Voltage Solved With Video

Have you watched my video ? Might be as simple as that also no problem keep us updated.

[Wroxall Tony]

Re: 17IPS20 No Led Voltage Solved With Video

Well, progress (sort of!). The new 17IPS20 board behaves exactly like the original - no LED output. So not an instant fix. However, probing deeper, I have the following symptoms (on either board):
1. Pd between + LED output and ground: settles to about 115V (after an initial 190V or so)
2. Pd between - LED output and ground: about 5 V (measured at the same time with a second meter)
3. but pd between + and - LED output is close to 0 V! Is this strange result due to the circuit detecting the impedance of the meter across the output terminals? Results are the same whether or not the LEDs are connected to the output.
4. Meter shows an "infinite" resistance across the LEDs when detached from the supply board (meter connected either way round) - but surely a load of LEDs should offer a measurable resistance? Diode setting on meter gives the same result.
5. On switchon the screen briefly (less than 1 second) shows the "Hitachi" logo, so the LEDs can't be completely dead I guess.

so.... should I be pursuing a dead string of LEDs, and dismantle the screen completely to get at them, or worry some more about the power supply to them? I have watched your videos, and checked easy things like diodes but this is my first venture into flat-screen TV repair so I'm starting from base camp! Thanks....