rca mod dmg gameboy not working

http://www.google.nl/url?sa=t&rct=j...zkTSWBY2rYSuy6L6-R-V4Gg&bvm=bv.80120444,d.d2s

I did this rca jacks mod on a dmg gameboy. But for some reason . I can't hear the red / right sound on a headphone ?
Anybody got an idea ?

 

Check your ground connection (soldering).

The video shows that he bridged the ground on both RCA jacks then ran a single wire to the volume output ground. I personally would of run a single ground wire from each RCA jack to the ground on the Gameboy's output.

 

Thanks for your reply. Funny enough is it the red/ right sound that is connected to the ground when i check with a multmeter and does not work.
The white /left jack has no connection with the ground (after checking with the multimeter)and works great. Both are connected with a single ground wire.

 

This is a bad mod.

1) It's probably not line level (1.4 Vpp into 47k ohms)
2) The outputs are likely soldered in parallel to the volume attenuator which drags down the headphone amplifiers input impedance, as well as lowering the frequency response and adding noise to the headphone amp. Depending on the output impedance of the source buffer it's possibly (probably) inappropriate to drive cables at this point anyway.
3) You can use a 1/8" to RCA cable instead of modding at all (and this would give the volume adjustment the author notes is missing)

If you wanted a truly "pro" line level output (where ironically a fixed volume is desired), you'd install a fixed voltage-divider attenuator in parallel to the volume attenuator, with series ac coupling capacitors. The resistor ratio depends on the amplitude at max volume, but the output impedance (calculated by the two resistors in parallel) should be <1000 ohms. If the source impedance is too high/the divider loads down the source too much, you could put the attenuator in parallel to the headphone output instead. That said, if you aren't worried about the amplitude there isn't a reason to NOT to directly use the headphone output (hopefully with a mod-free adapter cable).

 

Since you have a good ground… then there has to be an issue with the RIGHT channel; check your soldering, make sure you have not bridged the solder points on the volume pots. Check your wire; make sure non-insulated area is not making contact with any other solder points/metal. Are your RCA phono connectors the same as what are used in the video... outer tab (ground) or do yours have a center pin with sleeve. Connect your L & R channel wires to the center pin and the GROUND to the sleeve.

* additional troubleshooting:

If your soldering and connections check out; unsolder the LEFT (white) & RIGHT(red) wires from the RCA jack. Connect the LEFT wire to the RED jack and check to see if sound is coming out from that output. If you get no sound, then the RCA jack is defective, likely bad shielding causing a short. If you are getting sound, then the problem is with the RIGHT output pot on the Gameboy. Move down to the lower volume pots and try those.

I did some reading on this mod and looked at several different methods for outputting sound from the volume pot. The top two pots ( (1)RIGHT & (2)LEFT respectively); volume cannot be adjusted as noted in the YouTube video. The lower volume pots, 3 (LEFT ), 4(RIGHT ), allow you to adjust the volume.

Volume Pot Pinout

You made mention that you were testing sound with headphones; ideally, you should use the lower pots (3 & 4) if headphones is what you intend to use most often ... allowing you to adjust the gain/volume. The upper pots, from my understanding would be more ideal for recording purposes even though you can use headphones.

Here are some links on different options for the Pro Sound Mod ... It all covers most of the same information.


Nintendo Game Boy DMG-01: Line Out Mod

Game Boy Audio Line Out Mod

Game Boy Pro Sound Mod

Hope this helps ...

 

Part of the reason for these Prosound mods is because the original GB has noisy audio output, which isn't exactly something you want if you're using it as a musical instrument. Kitsch-Bent is making new amplifier boards that completely bypass the original amp and would be better than a Prosound mod, but I'm not sure when exactly it'll be released.

 

It's hard for me to believe the HP amp is audibly noisy considering the nature of the sound and the amp's power (typically batteries).

In any case it doesn't make sense to build an amp board for line output in the first place--perhaps it's a replacement headphone amp? For line you can directly attenuate the ASIC output and drive the cable from the attenuator, no active electronics. You'd just install the attenuator in parallel to the first coupling capacitor. I can't suggest R values since I'm not sure about the amplitude.

My guess is that people are modding their GB's primarily for clearer bass as the relatively small coupling capacitors will attenuate the low frequency response of the speaker and headphones in the stock circuit. For line output this doesn't apply though since line input is high impedance and the capacitors are more than sufficient.

 

Thanks but i have done that mod and really want to do a rca jack mod.

 

The other mods - just throwing it out there... but did you try any of the troubleshooting suggestions that I outlined for the RCA mod that you were attempting?