SSI_400_14A01 Rev0.1 Backlight Inverter, Original or Updated Board?

[TrblShtr]

Originally Posted by nomoresonys

Found one, sent you a private message.

Cool I'll check it out thanks!

[nomoresonys]

Ah, I see, ok it probably is a better revision, the originals seem to have failed a lot.

[nomoresonys]

I think the one you linked might work because here's one that looks like your first one but has the same number as the revised one, I'm thinking they just made it better in revision 2, I guess: https://www.ebay.com/c/1673942382

[TrblShtr]

Originally Posted by nomoresonys

Ah, I see, ok it probably is a better revision, the originals seem to have failed a lot.

Yeah that appears to be the case with the old Rev0.1 boards.

Originally Posted by nomoresonys

I think the one you linked might work because here's one that looks like your first one but has the same number as the revised one, I'm thinking they just made it better in revision 2, I guess: https://www.ebay.com/c/1673942382

I think so too since the updated board has the same 14 pins as the original but I'm waiting for the seller to confirm this. The board you linked looks like a more recent (not updated) version of the older 14A01 which by looking at it should fit my friend's dynex as well. If the updated board doesn't fit, I'll most likely purchase that one instead.

Thanks again NMS!

[cheeky2]

Personally speaking I would be checking the fuses on the inverter first to ensure that the fault is down to the inverter. As I recall the output from the psu to these inverters is 24V. I have found that the mosfets (8pin smd sop devices) normally short out dragging the power supply voltage down (if the fuse doesn't blow). This originally threw me when the fuse didn't blow on the inverter and originally leading me to the psu failure (which it wasn't).
So get your meter out and check both sides of the fuses for 24V. Just be careful not to go probing around any part of the transformers for the ccfl tubes as stated before as they are around 1kv.
The fuse locations are the red oblong boxes and the mosfets are the white oblong boxes. There are more mosfets on the other side of the pcb which can also fail.
Make sure when checking the mosfets that you turn off all the power to the TV. They normally short out across all pins so easy to check quickly if you wish to with your meter. At least by diagnosing the fault you can be confident that it will point to one part of the failure of the TV. The output transformers can also fail as well, but cross that bridge once you have isolated the issue further. No point in jumping the gun!
Good luck

[TrblShtr]

Originally Posted by cheeky2

Personally speaking I would be checking the fuses on the inverter first to ensure that the fault is down to the inverter. As I recall the output from the psu to these inverters is 24V. I have found that the mosfets (8pin smd sop devices) normally short out dragging the power supply voltage down (if the fuse doesn't blow). This originally threw me when the fuse didn't blow on the inverter and originally leading me to the psu failure (which it wasn't).
So get your meter out and check both sides of the fuses for 24V. Just be careful not to go probing around any part of the transformers for the ccfl tubes as stated before as they are around 1kv.
The fuse locations are the red oblong boxes and the mosfets are the white oblong boxes. There are more mosfets on the other side of the pcb which can also fail.
Make sure when checking the mosfets that you turn off all the power to the TV. They normally short out across all pins so easy to check quickly if you wish to with your meter. At least by diagnosing the fault you can be confident that it will point to one part of the failure of the TV. The output transformers can also fail as well, but cross that bridge once you have isolated the issue further. No point in jumping the gun!
Good luck

Gotcha, I see what you mean. It looks like I'll be doing some extensive diagnosing later today to further pinpoint the cause of the problem. I'll post my findings as soon as I do using the picture as a reference. Thanks cheeky 2!

[dick_barton]

The video i suggested in my earlier post does show you how and what to check.

[TrblShtr]

Originally Posted by dick_barton

The video i suggested in my earlier post does show you how and what to check.

I will use it as well for referencing & post my results later.

Thanks again.

[nomoresonys]

Yep the fuse/s are easy to check, somehow I thought you already checked them.

[cheeky2]

Originally Posted by dick_barton

The video i suggested in my earlier post does show you how and what to check.

Yes the youtube video is a good reference, just be aware as stated the fuse maybe good but failed mosfet can drag the 24V down.

[TrblShtr]

Originally Posted by nomoresonys

Yep the fuse/s are easy to check, somehow I thought you already checked them.

I was just just going off of what I visually saw on the board but testing it with the multimeter pinpointed the problem.

Originally Posted by cheeky2

Yes the youtube video is a good reference, just be aware as stated the fuse maybe good but failed mosfet can drag the 24V down.

Ok, gotcha!



Alright so here are the results from testing both fuses & all 14 MOSFETS:

Fuses - "000" reading on both.

MOSFETS to the right of the connectors (6 total) - Near "000" reading on all 8 pins of each MOSFET.

MOSFETS to the left of the connectors (8 total) - Near "000" reading on 4 of the pins of each MOSFET however, the other 4 pins of each MOSFET displayed "1" or no reading indicating bad MOSFETS which = faulty inverter board am I right? I think its worth mentioning that my multimeter does have a diode test setting but it does not beep. I've attached a picture of the bad MOSFETS (I think) outlined in blue. Many thanks for the help and guidance guys I really appreciate it!

[nomoresonys]

Transistor testing, there's a bunch of videos about it: https://www.youtube.com/watch?v=KGcoOETCaEQ

[dick_barton]

Can you give me the mosfet number as printed on it

[dick_barton]

The 4 pins of the mosfet that face the HV transformers are all connected together i.e pins 5, 6, 7 & 8

With the set powered off, place your meter on any of those 4 pins and check to see if any of the 4 remaining pins (pins 1 ,2, 3 or 4) give a low reading ie short circuit.

Repeat this for all the 14 mosfets. Only takes a minute or two.

D1 and D2 (Pins 5 ,6, 7 & 8) are connected together on the circuit board

[TrblShtr]

Originally Posted by nomoresonys

Transistor testing, there's a bunch of videos about it: https://www.youtube.com/watch?v=KGcoOETCaEQ

I watched the video & to be honest its a little more complicated than it seems but I'm staring to catch on slowly but surely.

Originally Posted by dick_barton

Can you give me the mosfet number as printed on it

Will do after work, its currently 6:30A.M. here in Arizona.

Originally Posted by dick_barton

The 4 pins of the mosfet that face the HV transformers are all connected together i.e pins 5, 6, 7 & 8

With the set powered off, place your meter on any of those 4 pins and check to see if any of the 4 remaining pins (pins 1 ,2, 3 or 4) give a low reading ie short circuit.

Repeat this for all the 14 mosfets. Only takes a minute or two.

D1 and D2 (Pins 5 ,6, 7 & 8) are connected together on the circuit board

OK, I'll post the readings & some pictures later today.

Thanks again guys!

[TrblShtr]

Originally Posted by dick_barton

Can you give me the mosfet number as printed on it

Looks like you beat me to the punch with the MOSFET numbers.

Ok so after doing some more learning and testing, I'm about 90% sure I tested the MOSFETS correctly this time. The culprit is (as I initially suspected), bad MOSFETS! I was however wrong about which ones were blown; All 6 FETS to the right of the T-con connector showed zero readings and the ones to the left, (8) tested fine but some were somewhat on the low side so does that indicate that they're about to ? So it appears I will have to replace the board & once I do I'll post the outcome.

You guys are awesome many-many thanks for the guidance and information provided to get to the root of the problem! I know there are other components on the t.v. that when bad, are more expensive to repair. Thankfully this wasn't the case. Stay safe guys, read you all later, peace!

[dick_barton]

Originally Posted by TrblShtr

All 6 FETS to the right of the T-con connector showed zero readings and the ones to the left, (8) tested fine but some were somewhat on the low side so does that indicate that they're about to ?.

When you say on the low side, how low?
I have an inverter board (SSI_400_14A01 Rev 0.1 2008.11.13) in front of me which looks idential to yours where , with the meter set in diode mode, there is no reading between the top side (pins 5,6,7,8) and bottom side (pins 1,2,3, 4) of the mosfets. Meter remains at OL

[cheeky2]

Probably two of the top mosfets have gone which is affecting readings of the others, which is quite normal. I doubt very much if your lower mosfets are likely to fail I guess its your testing process is likely floored as the gate drives can give you a lower resistance compared to the others.
If you cannot change the components then sell the old board on ebay and someone will buy it and repair it. Who knows you may have sellers refurbishing the same boards in the USA that will be cheaper than getting another one.

[TrblShtr]

Originally Posted by dick_barton

When you say on the low side, how low?
I have an inverter board (SSI_400_14A01 Rev 0.1 2008.11.13) in front of me which looks idential to yours where , with the meter set in diode mode, there is no reading between the top side (pins 5,6,7,8) and bottom side (pins 1,2,3, 4) of the mosfets. Meter remains at OL

Between 001-003. By what I've read online, 0.4v-0.9v tests as a good FET.

Originally Posted by cheeky2

Probably two of the top mosfets have gone which is affecting readings of the others, which is quite normal. I doubt very much if your lower mosfets are likely to fail I guess its your testing process is likely floored as the gate drives can give you a lower resistance compared to the others.
If you cannot change the components then sell the old board on ebay and someone will buy it and repair it. Who knows you may have sellers refurbishing the same boards in the USA that will be cheaper than getting another one.

Ahh I see! I'm sure thats most likely the case because on the underside of the board, there are noticeable brown blemishes (burn marks) directly under the bad MOSFETS. The other side has no marks at all. As for the components on the board, I can change them but I'll just save myself the headache and purchase a new one on ebay for $24.99 and sell the broken one. The newer board looks to be a little more reliable since it has 1 individual transformer per tab (the ones that connect to the LEDs via the bridge) and should run a little cooler I hope! Pic below.

Many thanks.