NESRGB Power Issue

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ShredderN64
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NESRGB Power Issue

Post by ShredderN64 »

Hello, new user here. It would seem you are all intimately familiar with the NES, and as such, I seek your guidance and wisdom.

Recently I attempted to install Voultar's multiout QSB to my existing NESRGB install. Before this, everything worked perfectly, but I had the wires hanging out the back like a monster, waiting for this particular QSB. Now, embarrassingly, upon removal of the NES board, I had lifted a few traces. Using the CAD files of Redherring32's OpenTendo project (which I understand to be a 1:1 recreation of the original NES board) as reference, I ran wires from the pins of the damaged traces to their next respective point.

After putting on the QSB, I was horrified to find I had no power. I immediately assumed something had happened to the voltage regulator, but it was fine. In fact, power was going everywhere it should, to my knowledge. Upon further inspection, I realized the NES would power on just fine without the NESRGB board attached, even without the PPU. Furthermore, it will also power on if only the "top" row of pins are connected (see photos). Ensuring there were no shorts on the PPU and all pins had continuity with the vias directly across from them (except for DP0-7 and EXT0-3) I noticed the only one of these pins that did not have continuity to the via directly across from it was the CLK pin, pin 18. Out of curiosity, I directly wired the pin on the PPU to the via, but had the same result.

A few notes: I'm using a Triad power supply (although testing it with the NES-002 yields the same results) and the NESRGB2.0 2019 revision of the board. The only other modification to this NES is the removal of pin 4 from the CIC to prevent the classic blinking light that everyone knows and loves. I don't think any of these are relevant, but perhaps they could be clues.

Here is an Imgur gallery showing my reconnection of the traces and the power phenomenon: https://imgur.com/a/7H1OTLo

Any help would be greatly appreciated. This has been driving me up the wall for about a week and making me feel incredibly stupid, especially since I had a completely fine working console before this.

(Moderator edit: attached images and commentary to forum)
Attachments
The other side of the board showing reconnection of the lifted traces, pins 2, 24, and 36.
The other side of the board showing reconnection of the lifted traces, pins 2, 24, and 36.
Lifting the NESRGB board so only the "top" row of pins connect. Note the power light.
Lifting the NESRGB board so only the "top" row of pins connect. Note the power light.
The NESRGB board fully socketed with the power button pressed. No power.
The NESRGB board fully socketed with the power button pressed. No power.
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Ben Boldt
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Re: NESRGB Power Issue

Post by Ben Boldt »

It definitely seems like a short circuit on the NESRGB board. Please do not power it on for very long like this. Just a quick test of the power button (less than 1 second) should be OK, but something may burn if you leave the power on for very long.

I would recommend looking closely at all of the soldering that you have done. Try to find any place that has excess solder, possibly causing a short.


Edit:
For example, I am seeing what appears to be 3 shorts on this particular solder connection:
shorts.png
Those little thin wisps are either your stranded wire too long, or wisps of solder. If it is just solder, continuing to poke at it with a soldering iron tends to just make it worse. What happens is that your solder was too hot for too long and it oxidized. So now it gets all gloppy and sticky, and also not very shiny when it cools. What you want to do is remove that solder again and apply new solder quickly, and/or using flux. Using a lead-based solder will help with this sort of thing a lot.

I notice that a lot of nearby traces got the green scraped off as you were working. (The green coating is called "solder mask".) This is kind of an unavoidable thing with old circuit boards unfortunately, and the longer and more you work on it, the more green that gets removed from these old boards. You have to beware that solder will now stick and short to those traces where the green solder mask has been removed.
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ShredderN64
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Re: NESRGB Power Issue

Post by ShredderN64 »

Hi Ben, thanks for the reply. I should clarify that I only have things this way for testing - once working, everything will be properly anchored down, but with such an old board, I really don't want to solder and desolder the same area over and over and potentially warp the board. Also, I use Kester leaded 44/56 solder with my favorite beverage, MG Chemicals liquid flux.

That being said, that was definitely an ugly joint. Here's a picture of it corrected, but unfortunately, it has made no change overall.
Screenshot_20220613-082627.png
Also worth noting that this is on the row that when connected does have power.
unregistered
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Re: NESRGB Power Issue

Post by unregistered »

hi ShredderN64,

This reply may be a waste; but, maybe it will help?

Solder may be still connected to that line above.
Solder may be still connected to that line above.
Hope ^that displays… anyways, look toward the top center inside that orange circle. Now, I realize the pin your wire is soldered to sticks up; but, the edge of that solder is overlapping the solder mask on the line above your connection.

So, maybe your signal is still shorting out, if that over lapping part of the solder is touching [!!] a tiny removed section of that solder mask.


Otherwise, you’ve cleaned up that spot nicely! 😀
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Ben Boldt
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Re: NESRGB Power Issue

Post by Ben Boldt »

It is probably something on the actual NESRGB board since partially disconnecting it caused the power light to turn on. Do you have a magnifying glass and/or reading glasses? Look closely at all soldering, and with light at different angles. Maybe a flashlight. It can be very hard to see a short. Our brains try to "edit out" thin streaks of shiny light like that. I think it is unlikely to be any other problem.
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ShredderN64
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Re: NESRGB Power Issue

Post by ShredderN64 »

Happy Father's Day! I'm back with an update.

Unsure of how to totally remove the possibility of a short, I decided to go with the "nuclear option" and completely disassemble the mod and install it into another NES. Don't worry: since having its PPU replaced the NES originally shown in the OP is working completely fine.
PXL_20220618_225659725.jpg
Here is the new installation in a different NES, this time with no damaged traces! Unfortunately, I'm having the exact same problem.

So this 100% absolutely restricts the problem to the NESRGB board, but... Where? Again, the only adjacent pins with continuity are the ground ones, and if there was a solder splash I didn't see elsewhere on the board, it theoretically shouldn't power with the top row attached, as that's where it gets 5V from. What are the odds that after redoing this whole process, consciously avoiding shorts that I made a short again? Is it possible the board just got fried or damaged somehow?

I did however notice that the A2 and RST pins (according to the NESRGB legend) connect to ground. Is this normal? The joints look as clean as they can get, but something about it rubs me the wrong way, and unfortunately I don't have a working installation to compare it to.
lidnariq
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Re: NESRGB Power Issue

Post by lidnariq »

Neither of those pins should connect to ground...
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ShredderN64
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Re: NESRGB Power Issue

Post by ShredderN64 »

lidnariq wrote: Sun Jun 19, 2022 10:51 am Neither of those pins should connect to ground...
Looks like we have our diagnosis! I have no idea how I even achieved that, considering the distance between them and ground.
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ShredderN64
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Re: NESRGB Power Issue

Post by ShredderN64 »

Well, this isn't good. I have nothing connected to the board and A2 and RST are still connecting to ground. "Confused" doesn't even begin to describe my feelings.
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Ben Boldt
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Re: NESRGB Power Issue

Post by Ben Boldt »

If you share some really clear photos of both sides of the board, I will be happy to take a look if anything looks potentially shorted.
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ShredderN64
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Re: NESRGB Power Issue

Post by ShredderN64 »

Thank you for your willingness to help! Here are the best pictures I could get with close ups of where the PPU lives. Don't mind the flux stains! Let me know if you'd like me to verify the continuity (or lack thereof) between any points.
PXL_20220622_115645352.jpg
PXL_20220622_115620418.jpg
PXL_20220622_115635154.jpg
PXL_20220622_115604835.jpg
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Ben Boldt
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Re: NESRGB Power Issue

Post by Ben Boldt »

It seems that this chip is bad:
nesrgb.jpg
Not sure how or why that would happen. If you wanted to remove the flux, you can use rubbing alcohol from the drugstore. It won't hurt anything. But it should not really cause any problems to leave it on there either.

Sorry that won't be an easy chip to remove or replace. I can't imagine any other reason those 2 signals would be shorted to GND. Did you try your continuity tester in both directions to verify these shorts?

You might consider asking the seller for an exchange or at least replacing that chip for you because I am not seeing how this particular problem could have been your fault.

Edit:
I went back and re-read. You said the NESRGB worked previously before you removed it? Then I have to strike through my previous statement if we know that it wasn't broken from new. Please verify the shorts in both directions first, then we can continue to brainstorm how that could break. MAYBE it was ESD, but that is quite uncommon.
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ShredderN64
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Re: NESRGB Power Issue

Post by ShredderN64 »

Here's an extreme close up. The pins marked in red have continuity with ground.
PXL_20220622_115620418~2.jpg
I originally installed this about 2 years ago and have had zero problems with it. Now, I've never had a problem with ESD in my life, and I didn't rub the board against the carpet, but I won't rule it out.

Also worth noting I went ahead and reflowed the joints with some fresh solder, but it didn't change anything.

If the part does need to be replaced, it's no big deal, as this isn't my first SMD rodeo. Finding a vendor for this LC541A, however, may prove difficult.
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Ben Boldt
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Re: NESRGB Power Issue

Post by Ben Boldt »

"LC541A" is actually a device marking. The real part number is 74LVC541A:
lc541.png
You may want to double-check the measurements, but it appears that you need the package "SSOP" and NOT "TVSOP". Based on your images, the chip is approx. the width of 3 pins of the PPU; 0.3 inches = 7.62mm. That lines up with SSOP:
ssop.PNG
ssop.PNG (11.32 KiB) Viewed 2505 times
If you have some connections, or can register referring to a college that you went to, you may be able to get free samples from TI. They are really picky who they send samples to these days. They have 1 part like this available available at Digikey ($0.63 each):

https://www.digikey.com/en/products/det ... DBR/377509

Code: Select all

EDIT:
Sorry, they say 0 in stock, even though the search result says they do have it in stock...  More looking will be necessary.
Here it is from Mouser:
https://www.mouser.com/ProductDetail/Te ... 3sHA%3D%3D

If you are going to make an order, I would recommend getting some extras in case you mess up or in case the other one is bad too. Since the cost of shipping outweighs the part itself, you might browse and try throwing in some of the other parts as well if they are similar in cheapness. Let me know if you need help with that.

GOOD LUCK. Typically fixing things like this where 1 chip inexplicably goes bad, other stuff could have gone wrong too. I would say there is at least a 50% chance that replacing this chip will fix it. Another thing to think about is pins and sockets. You may need to be inserting and removing this board multiple times. If there is enough room in the NES, you may want pins and sockets so the whole board is easily removable.
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Ben Boldt
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Re: NESRGB Power Issue

Post by Ben Boldt »

I just noticed, one of your pins shorted to GND is VCC. When GND and VCC are externally shorted, the internal ESD protection diodes may make it appear that the other input pins are shorted to GND. This could mean that actual the problem is elsewhere.

Do you have a bench power supply? With a bench supply, it will be possible to supply a controlled amount of current and see if any part of the circuit board starts getting hot... That can lead you to the actual broken part.
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