Troubleshooting NES problem

[FoxMontage]

Hello,
A friend of mine gave me his old PAL NES to look at, and I'm wondering if anyone here has come across a similar problem and would be able to point me towards a solution. I have searched for a while but cant find anything that is like this specifically.
Here is a picture of the issue.

https://imgur.com/gallery/f7u7k

Many Thanks.

[Marmotta]

By far the most likely issue is dirty contacts, either on the cart or the 72 pin connector. Try giving the cart contacts a good clean with isopropyl alcohol or similar and if that doesn't work, then disassemble the console and do the same with the contacts on the 72 pin connector. If it's particularly dirty, you can also boil it for a few minutes to clean it up, but make sure it's completely dry before testing it.

[FoxMontage]

Thank you for the reply. I should have given more details: I have already replaced the 72-pin, and cleaned and tested the carts on another system and they appear to work ok. I'm wondering if there is a specific component or trace that might be the cause, or if the PPU is defective. Is there a general process for determining this, or is it a case of replacing components on a trial and error basis?

[Syntax]

Similar issues have occured with poor ppu fitment during NesRGB installations.

Try reflowing the ppu legs or checking the traces around it.

[FoxMontage]

I will try a reflow, thanks mate.

I guess next would be to check continuity of all the traces from the PPU to their destinations?

[Syntax]

If you look thru the nes RGB thread someone stuffed a ground trace on their ppu and had similar glitches ( if my memory is working correct today and not mixing stories together)

Maybe that post could help point towards the issue, but if it were me I'd just pump some solder and heaps of heat on each leg and see how it goes