Select button won't work on funnyplaying replacement motherboard GBA | Game Boy | Page 1

lone horizon Apr 8, 2024, 10:01 PM

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I have built a new GBA using the replacement motherboard from Funnyplaying, along with their laminated IPS screen and ribbon cable. I got plenty of modding and soldering experience, but did take a few goes to get the CPU stuck down to the new board correctly. I did lift one of the solder pads for one cpu pin on the right hand side. That trace goes to the last pin on the bottom left of the ram chip. I have run a fine jumper wire and insulated it away from the other pins with kapton tape and tested thoroughly, its all working fine. I have quadurple checked all pins on the CPU and RAM. Nothing is loose, they are all soldered down well.

Everything works great EXCEPT the select button. It won't work in games.... However it works fine for the hotkey functionality. I've manually soldered wires to the SEL, L, and R pads on the motherboard in order to bring up the OSD that way instead of using the touch sensor. It works no problem! Holding select for a second brings up the OSD menu, and you can tap select the go between the options, then hold select the close the menu. You can use the other built in combos for putting the board into sleep mode, and changing the LED brightness (all which use the SEL button) no problem!

The button just won't work in games though. For example mapping an item to select in a Pokémon game won't work. On boot the GBA holding start and select won't make the Nintendo logo disappear. But the button works for the OSD! I have desoldered the wire from the SEL pad on the motherboard just in case that was causing some sort of weird conflict. But no same issue.

I've used GBA DPAD test tool and all buttons show working except select.
I've tested continuity between the select button pad and its test point nearby and its fine. Ive also tested the trace from the select button to the CPU, thats fine too.
Just trying to think of what else to test or check... I appreciate any input or ideas! I'm starting to think the board is faulty?

glacial carbonBOT Apr 8, 2024, 10:01 PM

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Please remember to provide as much information as possible including all troubleshooting steps you have already taken. If this is a hardware issue, please provide clear in-focus images of the issue, PCB (circuit board), installation, and any soldering you have done. Help us help you, posts with insufficient information will be deleted

gritty ice Apr 8, 2024, 10:07 PM

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is the cpu pin making a good connection to the pad? is the cpu pin shorted to pins next to it? that's what I'd check next given your explanation.
your cpu seems a bit skewed/misaligned

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also, what is going on here?

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" I did lift one of the solder pads for one cpu pin on the right hand side. That trace goes to the last pin on the bottom left of the ram chip. I have run a fine jumper wire and insulated it away from the other pins with kapton tape and tested thoroughly, its all working fine. "
I read this, but it looks like you've bridged 2 pins on the CPU

lone horizon Apr 8, 2024, 11:35 PM

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It looks like that in the photo, but its not bridged. the pin has been lifted up slightly with kapton tape under it and then over top to isolate it. 100% its all good, probably just the angle of the photo.

yeah it does look at little missalighned at the bottom, but ive been over the pins multiple times checking to make sure they are solid and in place and not touching. can't hurt to check again though!

otherwise no ideas why select is working for combo keys but not in game? not any other traces i can check?

civic pecan Apr 9, 2024, 12:08 AM

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Without the OSD wires attached, what's the voltage on the select pad?

lone horizon Apr 9, 2024, 12:55 AM

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WIll check that when home. Whats the expected voltage?

civic pecan Apr 9, 2024, 1:09 AM

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The AGB CPU has in internal pull-up to 3.3V. I'm not sure if the IPS driver board has its own pull-up but it could rule out one of the issues by isolating the AGB CPU and seeing if it is pulling up the select input correctly.

lone horizon Apr 9, 2024, 2:00 AM

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Cheers will try that at home. Will dissconnect IPS screen and test voltage on the sel pad

lone horizon Apr 9, 2024, 7:39 AM

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@atomic loom

lone horizon Apr 9, 2024, 10:26 AM

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civic pecan The AGB CPU has in internal pull-up to 3.3V. I'm not sure if the IPS driver boa...

Hey there. This is correct!

The start button is pulling 3.3v, in fact every button I've tested is pulling 3.3v.

The select button however is pulling almost nothing. 0.4 to 0.5v

Not sure what to do next!

copper merlin Apr 9, 2024, 11:31 AM

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Sounds like your select pin may be floating on the cpu to me, try seeing if you have any loose pins in the bottom 10 or so, I don’t remember exactly which one it is but it’s in that area

civic pecan Apr 9, 2024, 1:36 PM

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lone horizon Hey there. This is correct! The start button is pulling 3.3v, in fact every bu...

Unfortunately, it sounds like a CPU issue. Probably too much heat on the CPU when transferring/reflowing caused the internal pull-up resistor to break.

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Normally I wouldn’t suggest this, but if you’re keen on trying and don’t have any other options, bridge the select input pin and start input pin. Then check to see if the select and start inputs trigger together when pressing either button. If they both trigger simultaneously, there might be a solution

lone horizon Apr 9, 2024, 7:24 PM

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Yes seems to be a cpu issue! It was off a faulty/corroded board.

Yeah bridging them will probably work. But what would be the solution if so?

copper merlin Apr 9, 2024, 11:05 PM

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bridging them is to test the supposed issue.

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if it doesnt trigger while bridged we can likely confirm its the pull up resistor

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doing it this way will give the select input the voltage it needs to trigger, so if it does, we can work our way outward to find the issue

lone horizon Apr 10, 2024, 12:45 AM

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Thanks! I will test this when home. If it does trigger, that means the internal pull-up resistor isnt toast?

lone horizon Apr 10, 2024, 7:19 AM

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Ok with a bridge the select pad now gets 3.3v, but button testing only triggers start, not both 😦

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I guess that means bad cpu on the inside?

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I do have another cpu I harvested awhile ago. Its clean looking but there is a slight bump on the bottom of it. Like a visible lump on the bottom. Not sure if that's normal or not...

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rn_image_picker_lib_temp_b49fa862-5ba3-4ffc-8e22-85706a245441.jpg

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Hopefully you can see that circular outline.

copper merlin Apr 11, 2024, 12:46 AM

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It’s not a great sign but it might work just fine

steep spear Apr 11, 2024, 12:52 AM

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Did you use hot air? It looks like the chip popcorned

lone horizon Apr 11, 2024, 2:48 AM

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I did use hotair. Usually its not a problem, but it came from a corroded board. Looks like it might have had some mousture in it still. I've learn't now if you suspect water damage then bake the board in an over first at low temp.

lone horizon Apr 11, 2024, 2:49 AM

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copper merlin It’s not a great sign but it might work just fine

it did not! impossible to get it sitting flush, which makes soldering very difficult

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The solution is to harvest another gba cpu when I come across a cheap working unit. Thanks for all the help! I have learnt a lot.

copper merlin Apr 11, 2024, 10:23 AM

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If you are getting inputs at all then it’s not really the same issue, but feel free to open another troubleshooting ticket, this one appears to have run its course

lone horizon Apr 21, 2024, 9:13 PM

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Just to follow up on this, used a different CPU and all buttons worked fine 🙂

#Select button won't work on funnyplaying replacement motherboard GBA