Anyone familiar with the Akai LCD3701AD?

[budm]

Re: Anyone familiar with the Akai LCD3701AD?

The transistor will have Vdrops on the Collector and Emitter pin, so if the Vsat spec of that transistor is lets say 0.50, then the Vdrops on the Collector resistor will be = 5.0V -0.5V = 4.50V.
Transistor is not a perfect switch so the Voltage between C and E will never be at 0V (MOSFET has very low Rds which can be in milliOhms range so it dissipates less power than Transistor), switch also has contact resistance usually rated in milliOhms.
Vrops x Current through the device = power dissipation of the device.

[Spork Schivago]

Re: Anyone familiar with the Akai LCD3701AD?

The transistor will have Vdrops on the Collector and Emitter pin, so if the Vsat spec of that transistor is lets say 0.50, then the Vdrops on the Collector resistor will be = 5.0V -0.5V = 4.50V.
Transistor is not a perfect switch so the Voltage between C and E will never be at 0V (MOSFET has very low Rds which can be in milliOhms range so it dissipates less power than Transistor), switch also has contact resistance usually rated in milliOhms.
Vrops x Current through the device = power dissipation of the device.

When I was taking a shower a few minutes ago I remembered the word I was looking for, voltage drop. I edited my original post and added the voltage drop. That's what I was talking about. And that's why when that transistor is closed, a voltage less than 2.5VDC goes to pin 6, but when it's open, a voltage higher than 2.5VDC goes to pin 6, kicking on the PSU.

I think a bad MT8202 could explain the rapid blinking of the screen. I bet there's some sort of power on self test the processor goes through, and when something goes wrong, it blinks like that. I bet maybe a surge hit the TV or something and fried that CPU. It could have been that bad cap by the analog tuner I replaced that broke the processor, but I don't think that's the case.

What do you think Budm? Time to try replacing the MT8202E?

[budm]

Re: Anyone familiar with the Akai LCD3701AD?

'That's what I was talking about. And that's why when that transistor is closed, a voltage less than 2.5VDC goes to pin 6, but when it's open, a voltage higher than 2.5VDC goes to pin 6, kicking on the PSU.'
Vce will be <1V when Q21 is on.
When Q21 is OFF, the Vce of Q21 will depends on the load resistance connected to pin 6.

[Spork Schivago]

Re: Anyone familiar with the Akai LCD3701AD?

'That's what I was talking about. And that's why when that transistor is closed, a voltage less than 2.5VDC goes to pin 6, but when it's open, a voltage higher than 2.5VDC goes to pin 6, kicking on the PSU.'
Vce will be <1V when Q21 is on.
When Q21 is OFF, the Vce of Q21 will depends on the load resistance connected to pin 6.

Okay. And the PSU needs 2.5V generally on PS_ON to kick on, right? I think I got this now.

You think that U12 MT8202E is bad?

[vinceroger69]

Re: Anyone familiar with the Akai LCD3701AD?

ive just watched reece video he posted regarding this psu and mainboard with capacitor issues etc did you check the inverter capacitors just in case there bad too.

[Spork Schivago]

Re: Anyone familiar with the Akai LCD3701AD?

ive just watched reece video he posted regarding this psu and mainboard with capacitor issues etc did you check the inverter capacitors just in case there bad too.

No, I did not. However, when I jump started the PSU and made it turn on, the backlight CCFL tubes light up, so I'm assuming there's nothing wrong with the inverters. If the caps on the inverters were bad, wouldn't it prevent the backlight from lighting up?

Another thing, the part number for this board is: e3761-058010-4

I found a bunch on e-bay. They're not too expensive, but not one of them seem to have that red jumper cable that goes from the T-CON over to somewhere near the second main board. Not sure why that jumper and the other jumper on the bottom side are there.

ShopJimmy's picture of the board had the jumper cables but they're out of stock and said they're not planning on getting one anytime soon.

Should I pull every single capacitor on the main board and test them? Or is there anything else that I can do to test? I'm tempted to order one of those 30$ off e-bay and see if they work, but I'm sure there's a reason for those two jumper wires. Maybe it's to enable a different type of video format (like PAL?) I dunno. The customers aren't originally from America. I'm assuming the TV was bought in America though. I can't really see someone paying to have one shipped over sea and stuff.

Thanks.

[Spork Schivago]

Re: Anyone familiar with the Akai LCD3701AD?

B7 is where 8202UP3_1 connects to the BGA component. I see that on page 19 in the left hand side.

If I order the chip, I'm thinking of recapping the board as well. I wonder if I should recap the whole TV. The PSU, the mainboard, the second smaller daughter board, maybe even the inverters....I dunno. What would you guys do? And how much should I tell him it'd cost to do it all?

[Spork Schivago]

Re: Anyone familiar with the Akai LCD3701AD?

We removed the heatsink and can see the chip is an MT8202AG by MTK (MediaTek I believe). It says:

M (with two rings around it, kinda like Neptune's rings)
MT8202AG
0629-ADSL
FB164F11

From the schematics, I see there's some pins for an RS232 connection.

Page 75 in the service manual shows me that I can hook up something called a RS232-VGA download line to the VGA port of the main board and then connect the other end of the RS232-VGA download line to a computer's COM port. It gives me baud rate and other settings. Then it tells me to use the MTKTool and shows me how I can backup the software on there and flash new software. So, that means (at least to me), just replacing this chip isn't enough. Somehow, I'll have to get the firmware off the chip.

From what I've been reading in the service manual, I need the TV on in order to do that. What do you guys think? Page 81 (the last page) of the service manual shows me how to make one of these RS232-VGA download lines. Just need a D-SUB 15A (VGA) male connector and a D-SUB 9 (RS232) male connector. I already have a D-SUB RS232 cable around here somewheres. I'll probably have to order the D-SUB 15A though. I also have a RS232 to USB adaptor, although sometimes that doesn't work with certain softwares. I wonder if it'd work with the MTKTool. I'd have to find a copy of that tool as well.

[vinceroger69]

Re: Anyone familiar with the Akai LCD3701AD?

No, I did not. However, when I jump started the PSU and made it turn on, the backlight CCFL tubes light up, so I'm assuming there's nothing wrong with the inverters. If the caps on the inverters were bad, wouldn't it prevent the backlight from lighting up?

Another thing, the part number for this board is: e3761-058010-4

I found a bunch on e-bay. They're not too expensive, but not one of them seem to have that red jumper cable that goes from the T-CON over to somewhere near the second main board. Not sure why that jumper and the other jumper on the bottom side are there.

ShopJimmy's picture of the board had the jumper cables but they're out of stock and said they're not planning on getting one anytime soon.

Should I pull every single capacitor on the main board and test them? Or is there anything else that I can do to test? I'm tempted to order one of those 30$ off e-bay and see if they work, but I'm sure there's a reason for those two jumper wires. Maybe it's to enable a different type of video format (like PAL?) I dunno. The customers aren't originally from America. I'm assuming the TV was bought in America though. I can't really see someone paying to have one shipped over sea and stuff.

Thanks.

If this was my set i would probabaly try a ebay replacement board you may be able too use it without the jumper wires fitted or have to refit them i would try too get a mainboard that matches your panel number as a better chance it will work ok then as you say if you manage to replace that ic ok you the may have to find the software for it.

[Spork Schivago]

Re: Anyone familiar with the Akai LCD3701AD?

If this was my set i would probabaly try a ebay replacement board you may be able too use it without the jumper wires fitted or have to refit them i would try too get a mainboard that matches your panel number as a better chance it will work ok then as you say if you manage to replace that ic ok you the may have to find the software for it.

Even though I really want to fix the board, I think you're correct. Used boards aren't that bad. I searched for the board number. E-bay shows the TV model number with that board.

What the heck are the jumper wires used for? This could be important. Even if the board without the jumpers works, depending on the purpose of those jumper wires, it could be a problem for the customer. Perhaps they allow him to watch a different video format (like PAL for instance?) One goes from the T-CON connector J10, pin 27 to D80 (D80 says 203 on it). On the back, one jumper goes from the DIM GND BL_O/N connector J15 on the DIM pin I believe and it looks like it goes to the T-CON connector again, but on the back of the board. To either a pad or maybe a resistor. Above the spot, it says
R30
R91

but I don't see a resistor anywhere. It looks like the solder bridges the pads. I'm guessing the R30 and R91 is for the pads. Like R30 might be the left two pads (they're vertical, not horizontal) where a resistor might go, but isn't there. And then maybe R91 is for the rightmost two pads that are bridges with solder. There _might_ be an SMD resistor hiding under there, but being bridged like it is, I can't see why they'd do that.

The hot glue is the same colour as the hot glue on all the connectors, so I think this was done at the factory or at least the same time the glue was applied to the various connector wires. Not by someone else at a different time.

If I purchase a board that doesn't have the wires, perhaps the firmware is different and if I add the jumper, it might break something? Or because there's a daughter board with another BGA component, what happens if the firmwares aren't compatible? Perhaps one firmware depends on the other. There's also a DVD player built in. This worries me too. Maybe it depends on some key in one of the firmwares and if the chip is replaced, the DVD player might not be able to properly decrypt the DVDs.

What do you guys think? Just purchase a replacement board and go from there?

[Spork Schivago]

Re: Anyone familiar with the Akai LCD3701AD?

This is the replacement board we're thinking about purchasing:

http://www.ebay.com/itm/Akai-LCT3701...MakeTrack=true

It's 21.99$ with 7.35$ shipping.

The part number on the board is E3761-058010-4. In the service manual, I see 771E37AD02-02. This item says 771E37AD02-04. I don't see the 771E37AD02-02 anywhere on this board or anything like that. I'm hoping that e-bay one is compatible and if it is, I'll just buy that.

[Spork Schivago]

Re: Anyone familiar with the Akai LCD3701AD?

The new board came. It was pulled from an Akai LCT3701AD but it's a different board. No jumper wires but also, the old board has an RCA connector or whatever you want to call them that's black in colour. The new one has an plate right there and no black cover. Other than that, everything looks identical. Same caps in the same area, same resistors, etc.

I plug it all in. I hit the power button, I hear the DVD player power up. I see the back light kick on. I flip the TV up to see what's on the screen, no OSD. So I hit buttons, like volume up, down, channel up, down, video source, menu....nothing happens.

Should I try hooking a video source up or something? Any ideas?

Thanks.

[Spork Schivago]

Re: Anyone familiar with the Akai LCD3701AD?

I took some measurements for the buttons on the main board. All of them are reading around 3.3VDC and stay there, even when they're pushed, except for menu. Menu reads 3.3VDC (or 3.34VDC) and when it's pushed, it reads 0.00VDC, when it's let go, it reads 3.3VDC. None of the other ones do anything though. I don't have the remote control to try with the remote to see if the key board is bad or not.

[vinceroger69]

Re: Anyone familiar with the Akai LCD3701AD?

in the ebay picture you can see some numbers printed on the pcb E3761-
whats the full number on your original board we cant see it in the picture as too dark to read it.
i guess this replacement board dosnt match your panel exactly so you may need to see if there willing to give you a refund whilst we try too locate the correct main board

i wonder what would happen if you swopped the old eeprom to your new board?
maybe budm can offer some advice

[Spork Schivago]

Re: Anyone familiar with the Akai LCD3701AD?

Vinceroger69,

They said so long as it was going into the same TV, if it didn't work, they'd refund me. I told them the jumper wires weren't on their board and thought maybe it was just a newer revision. I agreed that if I did need to send it back, I'd pay for the return shipping and they'd refund me, minus whatever they paid for shipping.

The model number on the old board is:

E3761-058010-4
16-06-2006

The number on the new board is:

E3761-058010-4
16-06-2006

Exactly the same numbers and came from the same make and model TV. There's also a daughter board on this TV that connects to J41 on both boards.

I believe there's firmware on the MT8202AG because the service manual tells me how to back it up and update it, using a custom made serial cable. A DB-9 on one end and a VGA end on the other. I just wire two wires into the VGA end and plug it into the VGA port. The instructions say plug it in and turn on the TV. I can't turn the TV on with the old board, so I'm not sure I'll be able to pull the firmware off to put it on the new board.

They also give me instructions on how to do the firmware stuff on another chip. I'm thinking it's the daughter board but because there's a heatsink on the chip on the daughter board, I cannot confirm the part number of the BGA component.

I could not find this board with the jumper cables for sale. I thought about wiring the jumper cables myself and seeing if it fixed the problem, but without knowing what those freaking jumper wires are for, I think this is a horrible idea. They seem to go to the T-CON board and have something to do with the DIMMING pin from what I can tell. J15. The one that says DIM GND BL_O/N

[Spork Schivago]

Re: Anyone familiar with the Akai LCD3701AD?

Another thing I'd like to add, I think I found Akai's website:

http://www.akai.com/locate.php

I've never heard of Akai televisions before and have never seen one for sale. From their website, it almost looks like this isn't an American television. The doctor who brought it to me wasn't born in America. There's a chance he might have gotten it overseas. Could this have something to do with the jumper wires? Not sure how I should proceed. There's no technical support on Akai's website for any country.

I'd hate to send this board back and not be able to fix the TV. Wonder what would happen if I unhooked the daughter board there. It's got another tuner on it but I believe that one is for digital TV, not analog.

Would it be a good idea, just for testing purposes, to unhook the daughter board and the DVD player? I was thinking maybe the firmware on the daughter board might have to match the firmware on the main board here....or maybe the daughter board is broken as well?

[vinceroger69]

Re: Anyone familiar with the Akai LCD3701AD?

yes i see what you mean now about the firmware etc its a pity you cant find a exact match board with all the jumper wires on already asyou say theres also a rca socket missing and not sure why the side buttons are not working

[Spork Schivago]

Re: Anyone familiar with the Akai LCD3701AD?

I also found another difference. The new board doesn't have a CE95 cap and it DOES have the CE107 cap. The old board has both, CE95 and CE107 capacitors. Also, right next to those two caps on the old board, there's two surface mount components labeled L57 and and L69. Right above that are two empty spots, L56 and and L68. On the new board, they're switched. L56 and L68 are populated but L57 and L69 are not.

The caps and the SMD components I'm talking by are next to the T-CON connector. On the old board, the jumper wire is real close, maybe 1/2" away from these. I wonder if I should remove the cap FROM CE95 on the old board and put it in CE95 spot on the new board and switch those L#'s around. That probably wouldn't be a good idea though, right? I'm sure there's a reason they're not on the new board....

[Spork Schivago]

Re: Anyone familiar with the Akai LCD3701AD?

yes i see what you mean now about the firmware etc its a pity you cant find a exact match board with all the jumper wires on already asyou say theres also a rca socket missing and not sure why the side buttons are not working

ShopJimmy had them originally. I contacted them asking if they knew what the jumper wires were for. They said they didn't know because it had been so long since they actually had one and referred me to BadCaps.net. I told them you guys usually recommend ShopJimmy when I need a board and had already asked but you guys didn't know.

They said if you guys couldn't figure it out, they'd probably never know either but if they had the board, they could at least try. Unfortunately, they don't think they'll ever get one, ever, ever again.

I'm going to try plugging in a video source to see what happens.

Is there a chance that when the TV has lost power and it comes back on, it goes into an auto-setup mode and volume +/-, channel +/-, etc doesn't work until things are set? And I'm just not seeing the menu because of something with the dim jumper wires? I would think any menu that might pop up would let me navigate through with the buttons...

Can I safely unhook the daughter board and the DVD board? The daughter board just has a digital tuner and one of those audio connectors that have the black plug on it, for fiber I think, not sure. It's a square plug. I see them in fancy sound cards.

[vinceroger69]

Re: Anyone familiar with the Akai LCD3701AD?

its one of those situations do you risk damaging the new board you have just got or return it for a refund ? then its then trying too find the correct board i guess which maybe hard to locate. this is quite a old set to 10 years ish old so ccfls will be getting aged too so may go soon, hard too say what too do as we all like repairing and saving sets but its when to say its not cost effective too repair them.

you have nothing to loose by trying a dvd through a scart lead etc or even try the built in dvd player as it may load and auto play.