NESRGB Power Issue

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Ben Boldt
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Re: NESRGB Power Issue

Post by Ben Boldt »

I had an idea. What if you test the other 74LVC541? Are all the same pins shorted to GND on that one too?
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ShredderN64
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Re: NESRGB Power Issue

Post by ShredderN64 »

Thank you for the extensive help, Ben. Went ahead and ordered some sockets and pin strips along with a few extra ICs and figured I may as well grab a fresh power filter cap while I'm at it. Definitely getting some overtime at work this week, so if I do have to make another order for more components, I'm not too bent out of shape about it.

If I don't win the coin flip on this one, what other components might be suspect?
Ben Boldt wrote: Thu Jun 23, 2022 8:06 pm I had an idea. What if you test the other 74LVC541? Are all the same pins shorted to GND on that one too?
Here's the guy on the right. Same as before, red goes to GND.
PXL_20220622_115604835~2.jpg
Obviously I'm not an expert, but this one appears to be working as intended.
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Ben Boldt
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Re: NESRGB Power Issue

Post by Ben Boldt »

That is very interesting. This definitely points to the first chip being bad. Actually, the 2 /OE pins on the second chip may be intentionally shorted to GND by the circuit board anyway, so what you are seeing on the second chip does look completely normal.
vcc_gnd.png
What you will want to do next is remove the first chip, since we almost definitely know it is bad now. Then test the second chip again and see if the VCC -to- GND short is still there, or if it went away. If the short goes away, that is great news. If it is still there, we keep looking to find it.

It is really important not to lift any traces when removing the chip, as that will make additional work way more difficult. The best way is to use a heat gun and hold onto the chip with a fine tweezer with very light pressure until it just lifts off. No pulling or prying, trying to wedge something under it, etc. When it is hot enough, it should come right off with zero force.
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ShredderN64
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Re: NESRGB Power Issue

Post by ShredderN64 »

Plop! With some heat from my trusty Chinese clone 858D and the slightest tap of my tweezers, the troublesome chip jumped right off.
PXL_20220624_194927722.jpg
VCC no longer shorts to GND, nor do A2 or RST. I suppose all that's left to do now is wait for the mail. :beer: 8-)
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Ben Boldt
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Re: NESRGB Power Issue

Post by Ben Boldt »

Cool!

It still worries me what could have broken that chip in the first place. Be sure to let us know how it goes putting in the new chip!
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ShredderN64
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Re: NESRGB Power Issue

Post by ShredderN64 »

Finally got my parts in! The new chip is a little bigger than the original, but I made it work.
Screenshot_20220703-043931~2.png
So, the good news is that the power is back! The bad news is that I now only have audio output through the multiout and just get a black screen. The NES's native composite output still works, so once again we're looking for something on the NESRGB board. My memory isn't the best, but I swear just before I started working on the hole to mount the multiout, I tested it with an s-video cable, which worked perfectly. To my knowledge, the only thing that would have changed between then and now is that I put the bottom RF shield on. Thinking it perhaps shorted something, I took it off, but nothing has changed.

I was so close! :cry:
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Ben Boldt
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Re: NESRGB Power Issue

Post by Ben Boldt »

Sorry to hear that. I am not sure what else we could try at this point without using an oscilloscope to look at stuff. Let us know if you have one and we can tell you some things to look at. You may also find someone willing to buy the broken one from you (I.e. maybe me).
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ShredderN64
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Re: NESRGB Power Issue

Post by ShredderN64 »

False alarm! Just fell into a noob trap with the pallette pads. I thought "OFF" meant the NESRGB would use the original NES pallette, but it's a little more literal in that it turns off the board. Jumped 3 to GND and we're back in business!

Ben, thank you so much for sharing your patience and wisdom with me. I am truly indebted to you and endlessly thankful. You are the MAN!

To whomever may have this problem ten years in the future, I hope this helps.
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Ben Boldt
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Re: NESRGB Power Issue

Post by Ben Boldt »

Oh awesome, I am happy that you got it working. I was completely out of ideas. :beer:
hudson187
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Re: NESRGB Power Issue

Post by hudson187 »

Hi! I signed up just to say I have the same exact problem, except on a brand new install of a NESRGB 4.0 board. The system powered on for a few minutes, but I noticed controllers weren't working. I powered down and it never came back. I did some tests and determined I have the same 74LVC541A part failure; most points have continuity to ground while the other one is fine. I have some on order from Digikey now to replace.
hudson187
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Re: NESRGB Power Issue

Post by hudson187 »

I installed the new chip and still the same issue. However, I uninstalled Voultar's QSB board and the NESRGB powered up. I think there may be a short either in the board or the FFC port; I've ordered a new QSB from Laser Bear. Will post update once installed.
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