NAD 7130 display lamps

Puddintane

AK Subscriber
Subscriber
Has anyone had any experience replacing/repairing the display in an NAD 7130 receiver? I've looked through quite a few threads here, but none seem to be the same as this one. A few of the bars in the display are out making it a bit of a guessing game to figure out what it should be saying. Here are a couple pics. The display should be reading 880, and the darker colored bars (like the bottom horizontal bar in the middle 8) are actually the burned-out areas. Are there lamps in there that need replaced, or is it something that causes this?

It looks like the black, plastic shroud that surrounds the front part of the display might be attached by pins that are pressed/melted on the back side of the board. Notice the round, black piece amid all the solder points on the back of the board. It seems like that has to be removed (cut, broken?) to get the display shroud/bezel to come off.



 
By the looks of it, probably burned led segments. Only answer to this is replace the whole seven segment display. As you most likely can't get a exact match replacement, all 5 have to go, and any new ones in.

If you want to know if those segments are burned indeed, remove a seemingly damaged one, also remove the first one to the left and swap that in in place of the damaged one. If it works fine, then the segment on the other display is indeed fried.
You can also test each one of the 7 segments in each display with your meter on Diode setting. There is a common pin.

As you say, remove that black frame carefully grinding off those melted tabs. You can use any light glue to hold it in place afterwards.

Depending on size, you can get the required new displays. Check out:

https://www.ebay.com/sch/i.html?_fr...play.TRS0&_nkw=led+7+segment+display&_sacat=0
 
By the looks of it, probably burned led segments. Only answer to this is replace the whole seven segment display. As you most likely can't get a exact match replacement, all 5 have to go, and any new ones in.

If you want to know if those segments are burned indeed, remove a seemingly damaged one, also remove the first one to the left and swap that in in place of the damaged one. If it works fine, then the segment on the other display is indeed fried.
You can also test each one of the 7 segments in each display with your meter on Diode setting. There is a common pin.

As you say, remove that black frame carefully grinding off those melted tabs. You can use any light glue to hold it in place afterwards.

Depending on size, you can get the required new displays. Check out:

https://www.ebay.com/sch/i.html?_fr...play.TRS0&_nkw=led+7+segment+display&_sacat=0

"Depending on size" looks to be the key. There are a zillion listings on that auction site, and I've yet to find one that's the correct size. Each piece is .4 x .75 x .225 (width x height x depth inches), and the numeral is about .33h. And it looks to me from examining the board that the pins are aligned parallel along the long sides (the height) of each piece (I removed the black plastic bezel but haven't unsoldered any of the LEDs yet). Is that right? I noticed that some on that auction site have a different pin orientation. Given a similar pin alignment, should any of them fit (as long as they're the correct physical dimensions)?

This one looks very close (albeit with six pieces), but I can't read the detail in the image with the dimensions.
 
Looks like those ones you linked to above may fit. You can download the datasheet here:
http://www.datasheetcatalog.com/datasheets_pdf/M/A/N/7/MAN71A.shtml
Dimension may be correct, but in order to be sure about pin out you better remove one. You may also find the original part code stamped. You also need to swap 2 of them to see if the failure follows the -seemingly faulty- display.

I just went through the AM/FM range to observe the display and noticed something. Only the second from the left display seems to have any defective segments. It has trouble with "8," because the top horizontal segment doesn't work (and that's the only segment in all of the pieces that doesn't work). But if it were displaying the numeral "1" (which uses only the two, far-right vertical segments) it does (or should probably) work.

So... if I were to swap just those two, do you think it's possible that the display would appear to work properly, since the far left LED only needs to display the numeral "1" when you're in that range on AM or FM (on FM it displays two digits to the right of the decimal, i.e., 101.75).
 
Correct; it'd appear to work fine. Each segment is an individual led. You wouldn't notice anyone is burned until required to display a given number.
Swapping the faulty display to a position that wouldn't require a certain burned segment will surely solve the issue.
 
Correct; it'd appear to work fine. Each segment is an individual led. You wouldn't notice anyone is burned until required to display a given number.
Swapping the faulty display to a position that wouldn't require a certain burned segment will surely solve the issue.

So I swapped the first and second, and that took care of that problem. But I guess the bottom segment of the middle LED is out too (as it was in the pic above--or at least it's erratic). So it looks like I'm going to have to replace them (or at least one, if I can find a match). I also found this one (here). I think I'll contact the merchant tomorrow to see if it's cathode or anode. The item listing says cathode, but in the specs it says anode. Otherwise, it looks to be the right size.
 
Another newbie question here. How do I know if the part I'm ordering has the right pins in the right config?

I was looking at some LED displays at an online merchant and trying to figure out the pin count/config on the modules. On the ones that I have there are 14 (or would be, if they were all there and being used). But mine have only 11 pins (and even though some of them are there, and there are through-holes in the board, they're not soldered--so I assume they're not even connected/used in the module). Using the layout for this part (see the "F, G Layout" middle of p. 2) mine have no pins at 4, 5, and 12. (I think I need part #5082-7751 there on that data sheet, but they don't carry that one). But if you check out this other part for example, there is no diagram for the layout. So assuming it has the right pins being used in the right position, can/should I just cut off the pins where there isn't a hole in the board?
 
I have one that had some display problems. Turned out to be crappy solder on the black ribbon cable that connects to the PCB.

After I touched up the solder on the cable it works fine.
 
In regards to this one. It says there's no pin at 5 and no connection at 4, 6, and 12. Can those no connection pins just be snipped off before installing them? (And the same for any other module that has similar "no connection" at 4, 5, and/or 12?

Edit: this module is the right physical size, and the display is only a tiny bit larger (.4 in.-- which would be preferable to one that was smaller than the original).
 
Edit: this module is the right physical size, and the display is only a tiny bit larger (.4 in.-- which would be preferable to one that was smaller than the original).

Agree!

Yes, any pin without connection can be removed and function won't be affected.
 
Ordered the new LEDs from Mouser. They're a hair taller than the original but look appropriate. Also, they're deeper red than the picture shows, but they all work now! Again, a huge thank you for all your help and guidance. AK rocks!

37463977130_9ef822aff1_h.jpg

37463977390_3fed3cc541_h.jpg
 
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