NES Top Loader no picture or sound w/ power

[shear_xear]

Hi everyone, I have a NES 101 “top loader” that is receiving power but absolutely nothing happens when the the system is on.  The system was recapped, and a new power regulator was installed.  It is receiving the power, and I attached a LED at the switch and that lights up (9v at the switch).  I even attached a composite video circuit and ran sound out through a composite jack and got nothing.  The PPU and CPU do not seem to be getting power.  The board looks super clean and I don’t see any broken traces.  Anyone have any idea where the fault might be?  Thanks!

Edited November 14, 2019 by shear_xear

[CatPix]

I don't know anout the NES Top Loader, but I would look after the switch. I think the NES use a very classic 7805 voltage regulator.

And it tend to die over time.

It's a chip that looks like this :

 

It's a very common cause of "doesn't work" and since it's located usually after the power switch, people liek you can measure 9 volts at the switch, or can even get a power LED on.

[shear_xear]

Unfortunately first thing I did was replace the 7805, so it’s something other than that.  I’m getting right about 9v there as well. 

[ApolloBoy]

7 hours ago, shear_xear said:

Hi everyone, I have a NES 101 “top loader” that is receiving power but absolutely nothing happens when the the system is on.  The system was recapped, and a new power regulator was installed.  It is receiving the power, and I attached a LED at the switch and that lights up (9v at the switch).  I even attached a composite video circuit and ran sound out through a composite jack and got nothing.  The PPU and CPU do not seem to be getting power.  The board looks super clean and I don’t see any broken traces.  Anyone have any idea where the fault might be?  Thanks!

You should probably rewire your power LED so that it gets 5V instead of the incoming 9V rail, you can’t tell if the console is actually getting 5V or not with how it’s wired up currently.

 

Have you checked to make sure you’re getting 5V throughout the console?

[shear_xear]

So both my working console (that I am comparing voltage to), and the non-functioning unit read the same 9v at the switch, but when the power gets to the 7805 they both show 9v going in, but only the working console has 5v going out.

[CatPix]

What does the non-functionning one reads? 9V? 0V?

I would suspect that either your replacement 7805 is toasted, or, if you get 5V at the pin but no power further after, then I would suspect a broken trace.

[shear_xear]

Yeah, I was thinking about swapping the regulator out again.  Seems odd it is getting the 9v in but not putting out 5v (or anything at all).

[shear_xear]

So I have replaced the replacement power regulator, and it still has 9v on one side and nothing on the other.  Where could the fault be?  Should the regulator take the power in and step it down to 5v?  

[CatPix]

Yes it should. If you have a working regulator (you could wire the input and ground and see if you get 5 volts) then there is a fault on the NES board itself. My best guess would be a broken ground, if you don't even get 5 volts at the regulator output itself.

Edited November 15, 2019 by CatPix

[shear_xear]

So, if it were a broken ground, how would I be able to fix it?  I have put in two 7805’s and they both give the same results.  I have never had one bad regulator, but two seems very unlikely.

[+-^CrossBow^-]

You need get a multimeter and set it continuity mode. Check that the Negative input from where the power plugs in, is making contact with the middle via for the voltage regulator. That is the ground. Also check for continuity from that center pin for the VR to other ground points along the board to check if the ground is broken in some way. If you aren't getting a beep to indicate a good connection then:

 

You would just need to wire the center pin of the VR to another ground location on the board. On most PCBs then and now, there is usually a large ground plane all around the outer edge of the PCB. But if you have put in two VRs and both receive 9v on the input and nothing on the output, then you either have the ground via not making contact with the rest of the ground plane, or you are installing the VR in backwards though that last one isn't as likely since you usually have a heatsink next to them that you have to bolt them to flat.

 

 

[shear_xear]

Well, the first thing I did when I started to think the regulator wasn’t grounded was run a wire to ground, but that still didn’t work.  I will look at the negative input at the power jack.  Thanks!!