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Old 03-28-2018, 07:39 AM   #1
events.b
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Default Apex / Jensen JE3708 bad PSU, no 5VSB, can't find schematic

Hi,

I'm working on a Apex JE3708 with no 5V standby. Main cap is showing 160V as expected. The part number on the PSU is LK4180-001G, but I can't find schematics anywhere for it. I have identified what I believe is the smps controller for the 5VSB circuit, it's a small SOT-23 with markings "J135" or "J13S" on it, shown in the attached image. Can anybody help me identify what IC it is or maybe point me in the direction to find the diagram? Thanks guys.
Attached Images
File Type: jpg 20180328_093057.jpg (721.6 KB, 25 views)
File Type: jpg 20180328_093048.jpg (584.9 KB, 16 views)
File Type: jpg 20180326_112242.jpg (827.8 KB, 11 views)
File Type: jpg 20180327_102219.jpg (433.7 KB, 15 views)
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Old 03-28-2018, 07:55 AM   #2
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Default Re: Apex / Jensen JE3708 bad PSU, no 5VSB, can't find schematic

What are the part numbers given on IC1 and IC2?
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Old 03-28-2018, 09:37 AM   #3
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Default Re: Apex / Jensen JE3708 bad PSU, no 5VSB, can't find schematic

IC6 (6-PIN) is the SMPS IC for the standby power supply.
https://www.badcaps.net/forum/attach...0&d=1522244338
What DC V do you have on the big main filter cap on the top edge of the board?
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Old 03-28-2018, 01:16 PM   #4
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Default Re: Apex / Jensen JE3708 bad PSU, no 5VSB, can't find schematic

IC1 is unfortunately covered in epoxy and I cannot read it.
IC2 is ST Microelectronics L6599D

The big main filter cap carries 160VDC on it.
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Old 03-28-2018, 01:37 PM   #5
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Default Re: Apex / Jensen JE3708 bad PSU, no 5VSB, can't find schematic

I am talking about the main filter cap on the top edge of the board next to c22 where standby power supply section is, not the big main filter cap laying on its side.

Last edited by budm; 03-28-2018 at 01:39 PM..
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Old 03-28-2018, 03:28 PM   #6
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Default Re: Apex / Jensen JE3708 bad PSU, no 5VSB, can't find schematic

Oops, sorry, that one also has 160VDC.
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Old 03-28-2018, 03:36 PM   #7
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Default Re: Apex / Jensen JE3708 bad PSU, no 5VSB, can't find schematic

So the STBY power supply section has the 160VDC for it to work but it is not working.
Do you get STBY Voltage if you run the power supply by itself?
If not:
1) Then verify the diodes in the cold side of the STBY supply are all OK?
2) You can also try heating the STBY section to see if it will come on or not.
3) Check D1 and D3 in the hot side.
4) Check Startup/running caps C21 and the one next to it.
5) You have to get P/N of that 6-pin SMPS IC some how to be able to find out if the VCC has Voltage for it to run or not or by testing the DCV between the two legs of C21 and the C?? next to it.

Last edited by budm; 03-28-2018 at 03:38 PM..
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Old 03-29-2018, 07:47 AM   #8
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Default Re: Apex / Jensen JE3708 bad PSU, no 5VSB, can't find schematic

Hi,

After some googling I came across this:

https://elektrotanya.com/content/gab...00b-tap-panelt

It's Polish but it seems like they identified it as LD7535

datasheet for LD7535 is here:

http://www.leadtrend.com.tw/archive/...35A-DS-01c.pdf

What do you think? Do you agree? Thanks
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Old 03-29-2018, 09:05 AM   #9
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Default Re: Apex / Jensen JE3708 bad PSU, no 5VSB, can't find schematic

I also found this link, selling a "repair kit" for LK4180 power supply:

http://www.ohmsupplies.co.uk/epages/...roducts/KIT279

I emailed support and asked for IC6 part number, they told me it's this:

http://www.ohmsupplies.co.uk/epages/...jectID=5696877

SG6859

datasheet: http://www.mouser.com/ds/2/149/Fairc...926-795867.pdf

Seems pin compatible with LD7535. I have not checked all the details to see if they are truly interchangeable.
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Old 03-29-2018, 10:07 AM   #10
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Default Re: Apex / Jensen JE3708 bad PSU, no 5VSB, can't find schematic

Spec sheets.
LD7535A
SG6859a
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File Type: pdf LD7535A-DS-01c.pdf (393.2 KB, 8 views)
File Type: pdf SG6859a-305985.pdf (742.7 KB, 5 views)
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Old 04-03-2018, 09:08 AM   #11
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Default Re: Apex / Jensen JE3708 bad PSU, no 5VSB, can't find schematic

Found an opened resistor that supplies VCC power to the IC6. Replaced it and +5Vsb exists now!

Unfortunately still not standby LED and no sign of life, I suspect main board is faulty as well.
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Old 04-03-2018, 09:52 AM   #12
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Default Re: Apex / Jensen JE3708 bad PSU, no 5VSB, can't find schematic

Quote:
Originally Posted by stiv2k View Post
Found an opened resistor that supplies VCC power to the IC6. Replaced it and +5Vsb exists now!

Unfortunately still not standby LED and no sign of life, I suspect main board is faulty as well.
Please upload the pictures of the resistor in the location you found so it will help other people in the future.
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Old 04-03-2018, 11:31 AM   #13
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Default Re: Apex / Jensen JE3708 bad PSU, no 5VSB, can't find schematic

Circled in red, it goes directly to the VCC pin (pin 5) of IC6
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