AV modded 7800 missing sounds on some 2600 games

[Tifany]

Hey guys, I have an electronics sentimentalities AV modded 7800, I just got a harmony cart so was playing some games and noticed some sounds missing... the marching of space invaders, thrust of the ship in asteroids and several others. Any ideas whats going on here?

 

Thanks!

 

Tifany

 

 

[Osgeld]

When one av mods a 7800 they have to wire the 7800 sound and the 2600 sound together

 

I don't know if that applies here but it's my first guess

[Tifany]

OK, I played with it a bit more and figured out the white rca sound level is LOTS lower than the red rca out. So, on space invaders for example, the marching noise is still there, but at a much lower volume than your base shooting or the invaders exploding. is there an adjustment on that circuit that would even it out a bit??

[Osgeld]

probably, but I have only av modded 1 7800 in my life and it was mono, with the two audio sources "mixed" with a resistor, so i am not super familiar with how other mods work

 

(wisearse answer: fiddle with the balance on your tv, heh)

 

edit here is the post I referenced when I did mine

 

http://atariage.com/forums/topic/127926-easier-7800-composite-video-mod/?p=1543881

 

bout half way down shows the audio connections

Edited August 23, 2016 by Osgeld

[RevEng]

OK, I played with it a bit more and figured out the white rca sound level is LOTS lower than the red rca out. So, on space invaders for example, the marching noise is still there, but at a much lower volume than your base shooting or the invaders exploding. is there an adjustment on that circuit that would even it out a bit??

Electronics Sentimentalities uses the Longhorn Engineer 7800 video mod board. It's a mono mod, like all of them I'm aware of, but ES probably just split the mono into 2 feeds so you'd get sound to both TV speakers.

 

The mod mixes both channels of TIA audio by soldering the yellow mono-audio wire to the bottom of 2 resistors...

 

 

If you're hearing uneven audio from the TIA channels, then either the resistors aren't properly bridged, or there's a problem between the resistors and the TIA audio pins.

 

I'd start by checking that solder joint, inspecting it and/or pressing it while its running to see if the audio channel cuts back it. If it looks dodgy, or touching affects it, try to reflow the solder. (if you're comfortable with that sort of thing)

[Tifany]

Thanks for all the great info! Ill have to check it out when i get a free moment. Grad school just started again so my free moments are few and far between!

 

The mod should be mono, but im definitely getting different sounds from each channel. As in the space invader marching is coming through the left channel and the shot firing is coming through the right. I even tryed an rca Y adapter to sum the output and the sounds were still at different levels.

 

I need to see what it does with 7800 games as opposed to 2600 ones.

 

I may just send it back to him to check out and to give it a good cleaning.

 

Thanks again, ill let you know what i figure out.

 

Tif