JVC JLC42BC3000 screen froze on "JVC" logo.

[Langston]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

U18 (80-PIN IC), what is the P/N as printed on the top of the IC?
CE39 is the SMD lytics cap.

Thanks, I've isolated and sprayed U18 with no luck. Im very new to this and am not sure what the IC is. Could it be a bad SMD capacitor reacting to the cold?

[budm]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

Usually the bad cap will have high ESR when it is cooled and the ESR will go lower when it is heated up.
So right now it is a matter of pin pointing the bad part/s which is not easy when the board is crowded with parts.
There are parts on the bottom side of the board also.

[Langston]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

Usually the bad cap will have high ESR when it is cooled and the ESR will go lower when it is heated up.
So right now it is a matter of pin pointing the bad part/s which is not easy when the board is crowded with parts.
There are parts on the bottom side of the board also.

I've attach a picture and circled the spot where freezing temporarily fixes it. I also noticed there are two aluminum electrolytic capacitors in the circle CE15- "14.4" and CE24 "3.1" both caps say 14 220 16s on the top.

[budm]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

That looks like to be switching power supply or switched Power MOSFET, and those two are the filter caps, they look like to be 22uF 16V.
Can you read the P/N of that 8-pin IC?

[Langston]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

That looks like to be switching power supply or switched Power MOSFET, and those two are the filter caps, they look like to be 22uF 16V.
Can you read the P/N of that 8-pin IC?

I detached the board and looked underneath to find this HYNIX SEMICONDUCTOR H27UAG8T2BTR-BC. I sprayed it with upside down air can and sure enough it boots up as normal. Any idea if these are available and if so are there any special instructions for installing or is it just a desolder and re-solder swap? Thanks for any help! Much appreciated.

[budm]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

Nand Flash.

Were you able to do pin point cooling?

[Langston]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

Nand Flash.

Were you able to do pin point cooling?

Thanks, I'm doing my best to try and only cool the Nand flash. I taped the surroundings off but i'm sure its not 100% pin point. If I purchase a Nand flash is it a simple re-install or do I need to load it somehow with info? Sorry I'm very new to electronics.

[fzabkar]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

ISTM that the NAND flash IC would contain the firmware for the TV. Therefore you would need to copy its contents.

If the problem is indeed the flash IC, then ISTM that it may be affected by bad blocks. One way to recover from this would be to update the firmware, but that would require access to a factory utility.

Edit: AISI, the NAND flash contents would be copied to SDRAM at bootup, and program control would then be transferred to the code in SDRAM. The SoC would not need to access the NAND flash again until the next boot. This means that the TV should keep running without issue after it has booted. If this is indeed what is happening, then that would point to the flash as the culprit.

[Langston]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

ISTM that the NAND flash IC would contain the firmware for the TV. Therefore you would need to copy its contents.

If the problem is indeed the flash IC, then ISTM that it may be affected by bad blocks. One way to recover from this would be to update the firmware, but that would require access to a factory utility.

Edit: AISI, the NAND flash contents would be copied to SDRAM at bootup, and program control would then be transferred to the code in SDRAM. The SoC would not need to access the NAND flash again until the next boot. This means that the TV should keep running without issue after it has booted. If this is indeed what is happening, then that would point to the flash as the culprit.

Once I freeze the NAND and boot the tv it works properly until I turn it back off.

[Langston]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

I found one for sale-
https://secure.m.newegg.com/ShoppingCart
Is it a simple de solder and re solder? How do I program the nand flash? Thank you!

[fzabkar]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

I'm confident that the NAND flash IC is the problem, but I don't have much experience in repairing flat panel TVs, so I'm hoping that someone will provide a second opinion.

That said, if you decide to replace the chip, then you will need a chip reader/programmer to read it and copy it. The following article shows you what might be involved:

https://cdn.badcaps-static.com/pdfs/...c21b9c088a.pdf

It might be worth considering a different brand of NAND as a replacement (eg Samsung, Intel, Micron), but you will need to ensure that it is compatible.

[RADIOTRON]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

Have you able to fix this issue???? I have the same issue now.

[dc8frate]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

Thanks for this thread. I found the bad NAND chip using the freeze spray method and then I just cut to the chase, and sent the board to Ableman tv in Vancouver and they replaced the chip and updated the firmware. It works great, and I didn't have to buy a programmer for a one time job etc.

[NewAtThis]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

I have recently discovered this old but very helpful discussion. I hope that somebody more knowledgeable than me is still watching! I want to remove the main CB from the TV, which has the "stuck on JVC logo" problem. I have figured out how to disconnect all cables from the board, except one, a tiny ribbon cable, second from the bottom on the left side of the CB, as one looks at it from the back of the TV. The connector on the CB has a black part (the one farthest from the cable), which seems permanently attached to the CB, and a white part (the one closest to the cable). I thought that the white part is a plug that I could pull straight out, but I do not see how it can separate from the black part of the connector. Should it? Or should I pull the tiny ribbon cable itself out of the connector?? I want to post a photo, but I do not yet know how to do it.

Thank you in advance for any help.

[R_J]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

Post a picture by clicking on go advanced, then click the paper clip next to the smiley face, browse to your picture, click upload
Is this the connector? Tilt the black lever, remove the cable.

[NewAtThis]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

Thank you RJ. No, it's another connector. I'll post a photo as you suggest. Hm, I uploaded the photo, it tells me it's an attachment, but I do not see it here as part of my message! I'll click "submit" and see if it shows up. If it does not, I'll try to figure out what I am doing wrong. Sorry for my ignorance. I am really new to all this.

[NewAtThis]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

Well, since I did not know how to disconnect that little ribbon cable (see last posting), but I wanted to try to fix the "stuck at JVC logo" problem, I carefully turned the main CB upside down and rested it on a soft foam slab. (I had tried all the things recommended on this site, but nothing made the TV turn on normally. However, I had noticed that the capacitances of CE1 and CE22 on the main CB were unsteady with no power applied to the TV. I was aware that one cannot measure capacitance reliably while the cap is in circuit, but I thought I would give it a shot, since nothing else worked.) I replaced those 2 caps (it was hard to remove the old solder!). Beginner's luck: The TV turns on and off like a charm!!

Does anybody know what those caps are doing and why, if one or both are bad, the "stuck on JVC logo" problem will occur?

On the attached photo, the CE1 cap is circled. The CE22 is just to its left. Their nominal values are 220 uF/16V and 220uF/25V.

[budm]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

They are filter caps for the 5V and the 12V power suppliers, you should check the caps on the power supply board too.
According to post #4
F1= is for 5V power supply
F2= is for 12V power supply

[NewAtThis]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

Thank you, budm. I will when I have the opportunity to open the TV up again.

I have difficulty identifying the three components that are attached to the relatively large heat sink on the upper right quadrant of the PSU (please, see photo). I copied their labels and tried to identify them by searching online. They are:

Q201: 1615AU FQPF 13N06L. Online search found this to be a MOSFET.
D201: MBRF 10U160CT 122. Online search yielded nothing!
D202: MBRF 20U165CT 104 Online search yielded nothing!

If somebody could tell me what these are and what they do, I'll be grateful. I am trying to learn.

The 3 pins of Q201 have voltages 12.28, 13.15, and 14.47, but I am not experienced enough to tell which pin is the Source, which the Drain, and which the Gate.

Similarly, I cannot tell which pin is the Base, which the Emitter, and which the Collector for D201 and D202. (I assume that they are diodes, because JVC uses the symbol D for such.)

I measure strange voltages relative to the metal back of the TV for D201 and D202.

For D201: Pin 1: -0.06V, Pin 2: 13.15V, Pin 3: -0.06.
However, the voltage between Pins 1-2 is 2.8 - 3.2 V (i.e., it varies!), and that between Pins 2-3 is 2.6 - 3.4V (also variable). I feel lost.

For D202: Pin 1: -0.05V, Pin 2: 2.27V, Pin 3: -0.05V.
The voltage between Pins 1-2 is 5.30 V (steady), and that between Pins 2-3 is 5.33V (steady).

Thank you in advance for any help with this.

[budm]

Re: JVC JLC42BC3000 screen froze on "JVC" logo.

https://www.shopjimmy.com/vizio-0500...t-inverter.htm
Looks to be your power supply board.
Q201 () is the power MOSFET, it is used as a switch to provide switched 12V when PS-ON control signal from maia board is present.
D201 is the common Cathode diode, it is used for providing switched 12V.
D202 is the common Cathode diode, it is used for providing 5.2 VSB.
Look at the bottom of the board and you can easily see how those parts are connected and for what they are for if you have basic knowledge of electronics.
Are you 100% sure that the P/N you see on the diode is correct? Can you take good clear pictures?
MBRF 10U160CT
MBRF 20U165CT
Example of MBRF diode: