Question regarding ICs for a Neotec 2515C

Trakkur

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Hi again folks!

Over the weekend an associate and I worked on a Neotec 2515C monitor chassis that is simply NOT working properly. We have a vertical roll issue and some strange horizontal tearing.

This chassis was swapped into other games and displayed the same behavior, so we know that it is faulty. Solder joints were checked and reflowed, caps were all replaced but the issue still persists.

He told me that the last thing we should try is replacing the horizontal and vertical ICs. So I removed them from the board; one has the following markings, "LA7851 5A6" and looks just like a regular chip, the other is "LA7836 3G3" which is very small and sort of looks like a hair pick.

My questions are: Where can I find these? I've searched and found LA7836 and LA7851 but each has different 3 character codes underneath it...what IS that code? I want to be sure that we get the correct chips.

Thanks in advance for your help!
 
only concern yourself with the first set of numbers. The second set of 3 is a manufacture date code. Be weary of buying ANY ic off ebay, they are often counterfeit.
 
Thanks for the reply Ian - that's what I thought, but I wanted to be sure.

Do you have a preferred vendor for those ICs? How can I tell a counterfeit from original? I'm going to PinFest in Allentown, PA tomorrow - perhaps I'll find some there.

Hell, maybe I'll even find Robotron Video Decoder ROMs and/or a ROM reader/writer too. :)
 
look at the ICs in your monitor. pay close attention to the font/logo and when shopping on ebay try to find pictures that look like yours. The really bad counterfeits will have the wrong logo/font/placement of text/ etc. The better ones will at least look right as far as markings go but sometimes you can tell from the photos that something isn't right with the color of the IC. Its really hard to tell and it takes experience to spot, which is why I say stay away from ebay.

Might be worth checking with some of the repair people here to find one.

Just thinking about your particular problem, I don't think replacing the vertical IC will do anything for you. You should try to post a video of the problem, someone might know the solution.
 
Thanks again Ian. I've posted here, but thus far nobody has come forward with chips. I'll keep looking.

Regarding a video of the issue, I don't have one nor a photo - and I've removed the chips to get ready for replacements.

If I get a chance I'll replace them and take some videos, but more than likely I'll just find the chips and see if the issue is resolved.
 
I am one to verify something is bad before blowing money and trashing hard to find chips. It would at least make me feel better to see whats going on before you throw away the chips.
 
I completely agree Ian. I have not tossed the ICs, nor do I have any intention of doing so.

I will see if I have time tonight to reinstall them, hook up the chassis and try again...if I do I will be sure to take a short video and photos to document the results.

Thanks again!
 
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