L5973D IC info for Magnavox 32MD231D

[johnboy1313]

As in the links below, I found this IC (7003, L5973D) to be blown on the mainboard. I tried to be careful but I still managed to pull the entire pad from the center of the IC. All 8 pads for the legs are still attached, but the large pad that the body of the IC sat on is completely gone. I can't find any mention of the center connection on any of the data sheets that I've looked at. Do any of you know what the center pad connects to and what it does? Is it just for heat dissipation? If so, can I glue a small heat sink to it? Thanks

https://www.badcaps.net/forum/showth...ghlight=l5973D

https://www.badcaps.net/forum/showth...light=32mf231d

L5973D datasheet
https://cdn.badcaps-static.com/pdfs/...fae3fac721.pdf

[tom66]

Re: L5973D IC info for Magnavox 32MD231D

Exposed pad (EP). It's ground, and it's important to keep the IC heatsinked. Without it, you will need to bodge-on a heatsink.

[johnboy1313]

Re: L5973D IC info for Magnavox 32MD231D

Got the parts in today. Hopefully, the solid copper wire will act as a suitable heatsink. I haven't buttoned it up yet. I might glue a small heatsink on the top if you think I need to. We'll see how long it lasts.

[tom66]

Re: L5973D IC info for Magnavox 32MD231D

It won't, you need a better heatsink or the chip will fail again.

[johnboy1313]

Re: L5973D IC info for Magnavox 32MD231D

How's this?

[tom66]

Re: L5973D IC info for Magnavox 32MD231D

Overkill, but much better, I expect that to last. Remember to secure that IC down somewhere. If the TV is transported, it could fall off.

[johnboy1313]

Re: L5973D IC info for Magnavox 32MD231D

Honestly, I can't really think of a better way to do it than this. Remember, that's solid wire from a length of 12-3 for a house. It's soldered on really well. I really don't think it's going anywhere.

[fleetwise]

Re: L5973D IC info for Magnavox 32MD231D

You might solder the base of the ic straight to the ring teminal and leave the #12 wire out and cable tie the ribbons to the bracket you have the wire run under now.

[johnboy1313]

Re: L5973D IC info for Magnavox 32MD231D

I gave this exact same TV to my older brother to use as a computer monitor a few months back. I just spoke to him. He says it only gets used a few hours a week and never gets moved. He said I can swap the boards, no problem. At least this way, I won't feel like I sold a cobbled together piece of junk to someone. If it fails again, I can fix it for my brother fairly easy.

On the other hand, there's always the possibility that the other complete board will fail before this repaired one will. What do you think?

[johnboy1313]

Re: L5973D IC info for Magnavox 32MD231D

I've had a video playing on it all evening. I just went down to check on it and noticed the back light cut off briefly a few times. Each time the light would go off, there was a chirp from the PSU. Each time the light came back on, there was a chirp too. Looks like I need to dig a little further into this one.

[tom66]

Re: L5973D IC info for Magnavox 32MD231D

Does the sound get interrupted? You may have a cold joint or loose connector somewhere.

[johnboy1313]

Re: L5973D IC info for Magnavox 32MD231D

No, the sound continues fine. At this point, I'm not sure if its the PSU or one of the inverters. I plan on having a look tomorrow. In the meantime, I'm going to look around on the interwebs and see if I can find any info. Talk to you tomorrow, mate.

[johnboy1313]

Re: L5973D IC info for Magnavox 32MD231D

It would appear that my "repaired" main board is not as repaired as I had hoped. I've messed with it for nearly 2 hours and it's continuously cut off and on no more than 10 minutes after power on. It's quite possible that I'm getting ahead of myself, but about an hour ago I swapped a good board in from a 37MF321D/37 that had PSU issues and I've yet to see the no backlights fault re-appear.

When working correctly, pin 9 on connector 1089, "standby" shows 1.22V. Pin 5, "inverter-on-off" shows 4.0V. When the fault appears, the voltage at both pins drops out and the back lights cut off. Sound remains. Occasionally, the lights will flicker briefly showing a picture. It appears as if video is functioning the entire time. The power buttons and other controls work the entire time. When powered down, there is one LED lit on the main. When turned on, there are two.

I haven't tried to replicate the fault with a hair dryer because the components that I would think I need to focus on (see scaler attachment below) are all on the backside of the board.

7003 is the IC I replaced.

[tom66]

Re: L5973D IC info for Magnavox 32MD231D

The L5973D includes thermal shutdown. It is more than possible that the heatsink is not sufficient, the IC is shutting down, and you will need to do the job properly -- probably involving a new board, or mounting an external DC-DC converter.

[johnboy1313]

Re: L5973D IC info for Magnavox 32MD231D

These may be of help too.

[johnboy1313]

Re: L5973D IC info for Magnavox 32MD231D

The new IC was cooler than the rest of the board. When I removed it I could tell for certain that the other IC's on that part of the board were considerably hotter. The new IC was not warm at all.

[johnboy1313]

Re: L5973D IC info for Magnavox 32MD231D

The two round blue components in the middle of the attached pic were very hot as well. On the good board, they are only slightly warm.

[johnboy1313]

Re: L5973D IC info for Magnavox 32MD231D

The L5973D includes thermal shutdown. It is more than possible that the heatsink is not sufficient, the IC is shutting down, and you will need to do the job properly -- probably involving a new board, or mounting an external DC-DC converter.

I'm wondering if the original components relied on that IC being soldered where it is supposed to. Maybe by pulling off that pad, I severed the ground to something else.

[johnboy1313]

Re: L5973D IC info for Magnavox 32MD231D

I'd be more than willing to mount an external DC-DC converter if I knew which one to mount.

[tom66]

Re: L5973D IC info for Magnavox 32MD231D

Well, a switching converter requires a short loop, too. Likely you've got a few inches there each way? The converter is probably completely unstable. They're very sensitive.