SAE 2200 Power Level Display LED’s

??? Maybe we should backtrack to where you have 1.748 on the diode.(9 volts to the b input) You need to figure out why it doesn't get to the cap or pins 3 and 10 of the chips. Schematic shows it as a straight connection, I can't see from here why there is a difference....
 
I took both 6.8k resistors out of circuit. They are ok but will there be any harm to apply power to B in or A in with them out of circuit?
 
Shouldn't cause any harm, but I would still leave them in. I doubt they are the problem..
 
I don’t know what could be wrong. The led’s (except for the 5 that we’re out) were working and all I did was unsolder the two boards, replace all the lamps and solder everything back together. No other devices were originally removed.
 
I haven't found any manuals or pictures of the PC board - I may be able to look at a 2400L display (same, only different resistor on input leads), but will be away this weekend, so maybe next week. (no promises)
 
Thank you. What reading should I get on the pins that A in and B in connect to on the amp?
 
I don’t know what could be wrong. The led’s (except for the 5 that we’re out) were working and all I did was unsolder the two boards, replace all the lamps and solder everything back together. No other devices were originally removed.

As far as I can tell, you get the right voltages up to the diodes, then it doesn't make it to the inputs of the IC's, - which should be a direct line. That's why I want to look at the boards - I'm guessing there is a connection somewhere which wasn't reconnected when reassembling the displays.

Thank you. What reading should I get on the pins that A in and B in connect to on the amp?

There is no load, so the signal should be about a diode drop (if your input is DC to A or B) so 9 volts should drop to about 8.4, But, it probably will be lower as all the inputs of the ICs are connected to that point also.
 
I got a reading of .023V at the pins on the amp. The led board was removed. I received the LM324N’s today. Should I start installing them, U7 first?
 
*(if you plan to remove the IC s, I suggest to cut the leads, sacrifice the old IC to save the PCB traces, and desolder the individual pins) if you are experienced in desoldering you don't need to do this.

Anyway I'd look for something simpler first. Like some short or something not connected after the re assembling.
 
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Soldering and desoldering are not a problem.

There are pins that have to be desoldered in order to separate the two boards. I separated the boards and removed the 30 led’s and installed the new led’s. I checked each bulb to make sure they illuminated and they did. I then put the two boards back together. All the traces and pads looked good. I hooked the board back up to the amp and only lamps that illuminate are the first two. I can illuminate each of the other bulbs individually but they will not illuminate in operation of the amp. I have looked the board over very well and don’t see any bad solder joints although did reflow a couple that were suspect. Still didn’t work. I can apply voltage to the board with a 9V battery and illuminate each bulb so I believe the led’s are installed correctly. Does the -.001V on pins 5and 3 on U2, U4, and U6 indicate a problem?
 
This thing has really been taxing my pea brain. As I stated, all I did was separate the 2 boards (30 pins have to be unsoldered to separate the boards) replace the led’s and solder the two boards back together. So today, I revisited the 30 pins and reflowed the solder on a couple that looked suspect. Hooked the board to the amp and 4 led’s worked. I then replaced ic U2 and more started working. Went ahead and replaced U4, U6, U7, and U5 one at a time. Each time the unit became more stable. I’m going to replace the remaining two ic’s because I have the new ones and I’ve gone this far. I really believe that the problem was in the couple of solder joints that I revisited. I consider myself to be a pretty good solderer but apparently I didn’t do such a good job on a couple of pins and paid the price. It pays to check and recheck.

I want to express my gratitude for the help I got on this site. It is invaluable.
 
I'm glad you are getting it straightened out. Let me try to help you out with something else...

Take this pic [edit: pic deleted] and use it to replace the one you posted in post #5. (I have removed some things that are better left out.)
 
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Thanks. I don’t know how to delete the photo and replace it.
In the lower left corner of your posts you will see your name, a date and time, and then the word "Edit." If you click on the word "Edit" you can then change that post. To change images you need to click on the "More options..." button after you go into edit mode.

To add a new image, you can either save and re-upload a copy of the image I posted or you can incorporate the image that is part of my post. To do the latter, click on the "Media" icon media icon.png in the toolbar while you're in "More options" and then paste the link into the box where it says "Enter media URL".

You could also just put a note telling people to look at the image in post #33 (my post) and leave it at that.

To delete your original image use the "Delete" button next to the image as listed in the "Attached files" list (from within "More options").

I guess some of the above might be a little different for you if you are using a phone/tablet instead of a laptop/destop. When you have what you want, don't forget to click the "Save changes" button. If you use the browser back button from within "More options" your changes will be lost.
 
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In the lower left corner of your posts you will see your name, a date and time, and then the word "Edit." If you click on the word "Edit" you can then change that post. To change images you need to click on the "More options..." button after you go into edit mode.

To add a new image, you can either save and re-upload a copy of the image I posted or you can incorporate the image that is part of my post. To do the latter, click on the "Media" icon View attachment 1048766 in the toolbar while you're in "More options" and then paste the link
http://www.audiokarma.org/forums/index.php?attachments/img_1495edit-jpg.1048711/
into the box where it says "Enter media URL".

You could also just put a note telling people to look at the image in post #33 (my post) and leave it at that.

To delete your original image use the "Delete" button next to the image as listed in the "Attached files" list (from within "More options").

I guess some of the above might be a little different for you if you are using a phone/tablet instead of a laptop/destop. When you have what you want, don't forget to click the "Save changes" button. If you use the browser back button from within "More options" your changes will be lost.

I believe I have it all edited. Thanks again for your help. When I posted the original I didn't even pay attention to anything other than the board.
 
:thumbsup:
Q: Are the new LEDs brighter? Or can you really tell....
 
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:thumbsup:
Q: Are the new LEDs brighter? Or can you really tell....
They are a little brighter. The originals were a deep red diffused. The new ones I chose were red diffused. I think they look really good. I had to play a few minutes of Dark Side Of The Moon to test it out. Watching those lights is mesmerizing. Thank you so much for your help and patience.
 
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