Hi guys, I am fixing a GBA which suffered some corrosive damage to the board. After cleaning and repairing I noticed no soud at all.
So as I did in any other Gameboy restore I replaced the speaker but instead of giving crispy "loud" sound it went with super low volume. I examined the volume pot (which felt only a bit grainy) and having some new spare I decided to replace it. When carefully removing it I noticed some pads lifting up when warming the solder.. after removing I've seen some corrosion under them, that's why they unglued from the board.
I've seen on the internet an image of how the traces should have been and and used some wires to get the volume pot pins right where they should be.
Problem is.. from schematics I see they use not all 5 pins but only 3. Lets call V2 the mid, V1 and V3 the outers. For reference lets call P1 P2 P3 P4 P5 the real pins on the potentiometer. (so V1 = P1 , V2 = P3 , V3 = P5)
My damaged pads where P2 P3 P4 so.. looking at the schematics and at a pic with exposed traces only P3 should have been connected.
I connected P3 to Amp IC pin10 as it should and it has some sound but super low as said and sound wheel does not work in increasing or decreasing it. BUT if I connect P3 to P4 it begin to sould loud and crispy, and the volume wheel works flawlessy! On the loudspeaker and headphones too.
Looking at schematics and board picture with traces exposed it makes no sense..Does someone knows why? Looking at schematics..that pin is not even connected anywhere. Can it be because of the new pot being different from oem as internal traces? I bought from ebay..it said compatible with gba and gbc. The pot is good . i tried two and do the same.
Oh, one last thing.. I checked with my multimeter and the weird thing is if I check with only P3 it gives me about 20 ohm at max and about 9 on minimum.. if I join those 2 pins.. it can get down to about 3 ohm.
It has sense because of ohm law but.. still does not have sense on that GBA board.. I tried to find correc voltage/resistence values but no luck anywhere.. only something about the color but it uses the pot in a different way..so its useless.
For who is wondering why I am asking such a complicated question if the console works ok.. well its because it work in a way it was not supposed to do.. so I'd like to understand why. It would be a shame if this "mod" will mess the little amp or something else..
Thanks
So as I did in any other Gameboy restore I replaced the speaker but instead of giving crispy "loud" sound it went with super low volume. I examined the volume pot (which felt only a bit grainy) and having some new spare I decided to replace it. When carefully removing it I noticed some pads lifting up when warming the solder.. after removing I've seen some corrosion under them, that's why they unglued from the board.
I've seen on the internet an image of how the traces should have been and and used some wires to get the volume pot pins right where they should be.
Problem is.. from schematics I see they use not all 5 pins but only 3. Lets call V2 the mid, V1 and V3 the outers. For reference lets call P1 P2 P3 P4 P5 the real pins on the potentiometer. (so V1 = P1 , V2 = P3 , V3 = P5)
My damaged pads where P2 P3 P4 so.. looking at the schematics and at a pic with exposed traces only P3 should have been connected.
I connected P3 to Amp IC pin10 as it should and it has some sound but super low as said and sound wheel does not work in increasing or decreasing it. BUT if I connect P3 to P4 it begin to sould loud and crispy, and the volume wheel works flawlessy! On the loudspeaker and headphones too.
Looking at schematics and board picture with traces exposed it makes no sense..Does someone knows why? Looking at schematics..that pin is not even connected anywhere. Can it be because of the new pot being different from oem as internal traces? I bought from ebay..it said compatible with gba and gbc. The pot is good . i tried two and do the same.
Oh, one last thing.. I checked with my multimeter and the weird thing is if I check with only P3 it gives me about 20 ohm at max and about 9 on minimum.. if I join those 2 pins.. it can get down to about 3 ohm.
It has sense because of ohm law but.. still does not have sense on that GBA board.. I tried to find correc voltage/resistence values but no luck anywhere.. only something about the color but it uses the pot in a different way..so its useless.
For who is wondering why I am asking such a complicated question if the console works ok.. well its because it work in a way it was not supposed to do.. so I'd like to understand why. It would be a shame if this "mod" will mess the little amp or something else..
Thanks