Turbo Duo recap distorted audio and no left channel on headphone jack

[PapaSmurf]

I made some progress today.

I woke up early and finished recapping the left side of the board this morning.  The sound cleared up!  Perfect sound through the AV out and both channels on the headphones are now working.

The headphones are loud because I took off the volume knob to clean it.  There is also clipping on the HP jack.  I'm not sure if it's that the super-cheap Radio Shack headphones I'm using can't handle the loudness or because there is volume knob is missing.  Probably the latter.  I'll reattach the volume knob and see if the clipping disappears.  BTW, does anyone know a source for new volume knobs?

I just finished recapping the SMD caps in the CDROM area (previously I had only done the 3.3uf 50v one.)  So the Duo is now 100% recapped.  I'll test out the CD function tomorrow morning.

Here's the patient before I finished recapping today:

[gtsamour]

Good job !!!!! Anything is possible but I think its going to be hard to find the exact nob and replace it.
I don't remember about the DUO but on the CDROM2 unit, the sound signal on the headphone jack is indeed high when turned all the way up.... it causes distortion, not like static but more like a loud bass.

[PapaSmurf]

Good job !!!!! Anything is possible but I think its going to be hard to find the exact nob and replace it.
I don't remember about the DUO but on the CDROM2 unit, the sound signal on the headphone jack is indeed high when turned all the way up.... it causes distortion, not like static but more like a loud bass.

Thanks.  I'm really glad it's working this well.

It would be nice if someone could sell me the volume knob from a dead Duo board.  I found a new one online with the same dimensions and pin spacing.  It shouldn't be hard to retrofit it, provided that they are the same specs.  Does anyone know the pin out and the max resistance value for the Duo's volume pot?

I reinstalled the volume pot and it's definitely messed up.  It sort of works, but the lowest setting is still loud.  I noticed that, if I press down on the knob, the volume decreases a lot.  There's more physical resistance than there should be when you turn the knob.  I'm sure flux migrated into the pot when I was cleaning the board.  I've soaked it in IPA several times and it helped a little.  I'm going to remove it and soak it in IPA overnight, then test the resistance with a multimeter.

Other than that, it's working perfectly.  And luckily I didn't have to adjust any trim pots for the CD!

[NichlasEk]

The volume pot is a carbon film pot. That carbone trace dosent always fare well in IPA as it dissolves it. (I have screwd up once ore twice that way) The volume pot for the game geat seems similar. Etim sells the four legged version http://etim.net.au/shop/shop.php?crn=206&rn=516&action=show_detail. All other i have found are three legs but works as well if you link the grounds. Might not be the right value but might just work?

[PapaSmurf]

The volume pot is a carbon film pot. That carbone trace dosent always fare well in IPA as it dissolves it. (I have screwd up once ore twice that way) The volume pot for the game geat seems similar. Etim sells the four legged version http://etim.net.au/shop/shop.php?crn=206&rn=516&action=show_detail. All other i have found are three legs but works as well if you link the grounds. Might not be the right value but might just work?

You're right.  I vaguely remember cleaning my SNES controllers and removing the carbon from the rubber pads.

I tested it out again and it's working much better now.  One of the channels is louder than the other, and gently pressing the knob brings the volume on that channel back down.  I think this is a dual-gang pot; one for each channel.  A three pin single gang pot wouldn't work.

This pot looks like it will fit http://www.alps.com/prod/info/E/HTML/Potentiometer/RotaryPotentiometers/RKJ1/RK10J12R0A0B.html.  I ordered one, so in a few days I'll report the results.

The Game Gear pot looks like it's through-hole and the dial is a bit thick.  But it might work.  I'll keep it in mind.

Oh yeah, Happy/Merry Christmas everyone!

[Nodoka75]

Yep, it is a stereo pot on our dear DUO ^^

Right, on Game Gear the volume pot is a through-hole model.

[Keith Courage]

The original gameboy pot works as a replacement. https://www.ebay.com/itm/2PCS-Replacement-Volume-Switch-Repair-Parts-For-Gameboy-Color-GBC-Motherboard/182562243778?hash=item2a818ec4c2:g:8rgAAOSwBahVFAjn

gamegear pot is not compatible with a DUO. Even though it has 5 pins the pin order is different. However a game gear pot will work to replace the volume dial for a Turboexpress/Pc engine GT.

[PapaSmurf]

The original gameboy pot works as a replacement. https://www.ebay.com/itm/2PCS-Replacement-Volume-Switch-Repair-Parts-For-Gameboy-Color-GBC-Motherboard/182562243778?hash=item2a818ec4c2:g:8rgAAOSwBahVFAjn

gamegear pot is not compatible with a DUO. Even though it has 5 pins the pin order is different. However a game gear pot will work to replace the volume dial for a Turboexpress/Pc engine GT.

I soldered the Alps pot to my Duo today and it works, but I don't like the curve it has.  Only a few degrees turn and it gets loud, then the rest of the way increases the volume a little.  Also, the legs should be one or two millimeters longer so the wheel will protrude more.

Old and new pots:


KC, thanks for the suggestion.  I ordered that pot today and I'll try it out when it gets here from China.  The GBC pot is 2mm larger in diameter than the original Duo.  So that might help out if the legs don't quite reach.