Genesis Gen1 A/V mod

[wizzle]

I just modded my gen 1 genesis after having it in storage for the past decade or so and im having issues with it.

The composite video is perfect. there is no problem there.

the problem im coming up with is with the audio.

the audio chip works. it plays audio on the rf though it is VERY muffled (i suspect the port just has corrosion on the inside of it) but the headphone jack does not work proper. when i put on a pair of headphones i can hear faint sound but it sounds like popping noise and not sound effects.

i have grounded everything twice, unsoldered everything but video for troubleshooting, and even tried the mono sound from the din connector.

when theres color video the sound makes a buzzing sound that intensifies when theres more color on the screen.

the console is ntsc and worked fine before it went into storage.

i have cleaned it very well and have tried 3 different power supplies thinking that may be the issue.

there are no obvious signs of damage to the unit and im at a loss trying to figure out what the problem could be



any ideas?

[wizzle]

ok, so i just played around a bit more and have managed to get some audio from the mono output on the din connector.

so i am thinking the amplifier is bad because the audio coming from the din is VERY weak and i have to crank the tv volume way up to hear it.

soooo how difficult is the amp to replace and where is it at on the board?


(mods, i think i opened this in the wrong section, could you move it please)

[Midori]

It might be the capacitors that have dried up aswell. Although that is not a usual problem on the Mega Drive as far as I know... But it's probably easier to test to swap the capacitors than the amp.

The amp should be the CXA1034P chip.

[People?]

Clean the volume potentiometer with electronics cleaner (Deoxit for example) or alcohol. Pour generous amounts of it on the whole thing, then turn it up and down at least fifty times. Wait until it dries.

[bigsanta]

Clean the volume potentiometer with electronics cleaner (Deoxit for example) or alcohol. Pour generous amounts of it on the whole thing, then turn it up and down at least fifty times. Wait until it dries.

I noticed a strange problem on mine when i tested it's resistance levels.I started off with the slider at 0  volume (highest resistance )then slowly increased the slider's volume level until it was at full volume.What i noticed was the resistance started high,then went lower then it increased then dropped and  continued as you'd expect when it reached full volume.

Don't know the reason for that strange increase in resistance, when you'd expect a continuous drop as the volume increases .

[People?]

Clean the volume potentiometer with electronics cleaner (Deoxit for example) or alcohol. Pour generous amounts of it on the whole thing, then turn it up and down at least fifty times. Wait until it dries.

I noticed a strange problem on mine when i tested it's resistance levels.I started off with the slider at 0  volume (highest resistance )then slowly increased the slider's volume level until it was at full volume.What i noticed was the resistance started high,then went lower then it increased then dropped and  continued as you'd expect when it reached full volume.

Don't know the reason for that strange increase in resistance, when you'd expect a continuous drop as the volume increases .

Well, these sliding potentiometers get very, very dirty and when that happens, they're very unreliable. Clean it up and you'll probably get proper measurements from it. 80's audio gear usually used these, and they're unusable today, unless you clean them up.

[l_oliveira]

on any early MEGA DRIVE console, the volume is amplified through the  SONY CXA1034 chip for the headphones connector. But for the monaural output that goes to the DIN connector, it's amplified by one half of the small OP AMP which is right above the YM2612 then it's feed into the AUDIO BUFFER from the CXA1145 chip.

It's possible that the OP's SEGA GENESIS console is starting to suffer of bad capacitor syndrome. And capacitors from the audio circuitry are starting to fail.