Sega Mega Drive freeze issue and no sound issue.

[suverman]

Hi guys, this be my first post.

Please do not respond by asking me to just buy a cheap one off ebay or something.

I got a Sega MegaDrive with stereo sound(used to be). Got it used from a dubious place.


Now, I was using the Mega Drive 2 adaptor to run it, the console used to freeze within seconds
of startup screen of the game. Not always though, at times it got started and continued
without a problem. I didnt get proper tuning with the RF jack so I used the headphone jack,
andI could hear the sound faintly but with a lot of humming, eventually the sound just died.

I have since then acquired AV cable and a DC power supply that can supply 0 - 2A of current
and voltage can be set from 1- 16V. Its got 2 digital screens to show me the current being
drawing and voltage I set to 10V.

I have noticed this:
The moment I turn on the MD,

Current reads from .7 amps and gradually drops to .65 amps within 5 secs.
Eighter the game doesnt bootup or it just hangs.

Current reads from .7 and doesnt drop below .68 amps till the game starts
The game bootsup and runs, and usually keeps on running without ANY problems (except lack of sound).

If I drop the voltage to like around 7V, the current drops too, I can hear humming
sound from the headphone, but even when I tune the supply back upto 10 / 11V, the humming
goes away, but I can still hear no sound.


Questions:

1) When the MD is rated at 1.2A, why does it NEVER draw more than .75 amps? Infact each time it draws less than .68 amps at the booting time, the megadrive doesnt even run.

2) Sound dissapearing, shouldnt there be some visible evidence of say something burnt etc. How do I check
what is th cause for the sound to dissapear?

Thanks a bunch guys.

[bust3dstr8]

Questions:

1) When the MD is rated at 1.2A, why does it NEVER draw more than .75 amps? Infact each time it draws less than .68 amps at the booting time, the megadrive doesnt even run.

2) Sound dissapearing, shouldnt there be some visible evidence of say something burnt etc. How do I check
what is th cause for the sound to dissapear?

Thanks a bunch guys.

Answers....

1) Us mortals shall never know, maybe if you write to Sega's Develpment deparment
they will enlighten you.

2)Many things are not as the appear to the naked eye, I would fly to M.I.T. and see if they
will let you use their Gamma-Ray Pulse scanner.

[APE992]

Probably what was available cheaply and so they had headroom in case a Genesis revision needed more power than the last.

You NEVER get a power supply capable of exactly 100% of your "requirements". Just asking for trouble.

[suverman]

Answers....

1) Us mortals shall never know, maybe if you write to Sega's Develpment deparment
they will enlighten you.

2)Many things are not as the appear to the naked eye, I would fly to M.I.T. and see if they
will let you use their Gamma-Ray Pulse scanner.

A simple "I don't know." or better yet refraining from even posting something would have been
better that this useless sarcastic response.

[suverman]

Probably what was available cheaply and so they had headroom in case a Genesis revision needed more power than the last.

You NEVER get a power supply capable of exactly 100% of your "requirements". Just asking for trouble.

Yes, what I was getting at, was, is there any component that is failing, resulting in such odd behavior? Could it be faulty power regulator transistors? What happens if the transistors malfunctions?

[Sunnyvale]

Yes, what I was getting at, was, is there any component that is failing, resulting in such odd behavior? Could it be faulty power regulator transistors? What happens if the transistors malfunctions?

Methinks he's saying don't expect the specs to line up properly, they came outta the factory that way.

[APE992]

Methinks he's saying don't expect the specs to line up properly, they came outta the factory that way.

Indeed.


Yes, what I was getting at, was, is there any component that is failing, resulting in such odd behavior? Could it be faulty power regulator transistors? What happens if the transistors malfunctions?

That isn't odd behavior. 100% normal. If it was drawing above 90% of the rated maximum I might be a bit concerned but finding it as low as you did isn't anything to be concerned about.

What in the world made you think it was odd behavior?

[suverman]

What in the world made you think it was odd behavior?

The correlation of MD freezing or not booting up with the rapid fall in amps from .7 to .65; If falls but stays .69, it doesnt freeze, but runs properly (without music but)

[APE992]

Oh I see where you're coming from now. Though, correlation!=causation as you surely are aware.

My bet is that the lower current draw is simply due to the fact that the Genesis is sitting idle not doing any number crunching, data accessing or controller polling. Such a small drop could be accounted for.

After rereading your first post I think I can see a potential fix for the sound: capacitor replacement. If you can barely hear it then one/some/all capacitors have failed that are in the circuit pathway for audio. I had this happen on a NES of mine where I had to max out my amplifier to get the sound at normal levels; it also happens on GameGears with some regularity.

The freezing could be related or it could be related to using a MD2 power supply (how did you manage to get it to fit?) or due to dirty contacts/corroded contacts/neutrinos/Raptor Jesus. When cartridge based systems randomly freeze it can be very difficult to fix the cause if it isn't the cartridge or the cartridge slot. Could very easily be a broken solder joint somewhere that expands as it heats up just enough to cause the system to freeze.

[suverman]

Oh I see where you're coming from now. Though, correlation!=causation as you surely are aware.

Yea, Correlation does not necessarily imply causation. I am aware of that, which is why I asked you guys :)

My bet is that the lower current draw is simply due to the fact that the Genesis is sitting idle not doing any number crunching, data accessing or controller polling. Such a small drop could be accounted for.




After rereading your first post I think I can see a potential fix for the sound: capacitor replacement. If you can barely hear it then one/some/all capacitors have failed that are in the circuit pathway for audio. I had this happen on a NES of mine where I had to max out my amplifier to get the sound at normal levels; it also happens on GameGears with some regularity.


Ok, mind you I could not find a single capacitor bloated or leaking, but I shall give it a try. Yea, GG caps were the worst of the lot, even videos dimmed due to dying caps.






Could very easily be a broken solder joint somewhere that expands as it heats up just enough to cause the system to freeze.


5122

I also see a resistor attached (around the red dot) to one of the Zilog?'s pin, the processor being located just above the cart slot. Can this have an impact??? I havent seen such a resistor on any other MD photo on the net. I dont have access to another MD1, so.

I

[APE992]

Ok, mind you I could not find a single capacitor bloated or leaking, but I shall give it a try. Yea, GG caps were the worst of the lot, even videos dimmed due to dying caps.

I also see a resistor attached (around the red dot) to one of the Zilog?'s pin, the processor being located just above the cart slot. Can this have an impact??? I havent seen such a resistor on any other MD photo on the net. I dont have access to another MD1, so.


To the first sentence: that means nothing unfortunately. Caps dry out and become next to useless. Bloating and leaking aren't the only things they can do (they can also cook off and make a nice red mark in your foot).

The the second: it was probably installed as a fix for a design flaw at the factory. You'd be surprised how many boards I've seen that have bits of 30AWG running around for no apparent reason that, after speaking with an engineer from the company, makes perfect sense.

[jb143]

Bloating and leaking aren't the only things they can do (they can also cook off and make a nice red mark in your foot).

I had one blow up in my face once. Had a penny taste in my mouth for the next hour.



The the second: it was probably installed as a fix for a design flaw at the factory.
I can verify this. Not necessarily for Sega but in the electronics industry in general. I worked in electronics testing and repair right off the assembly line for a bit and it was quite common to make fixes like that. And then I moved into the engineering department and authorized work instruction deviations for similar fixes. For example, once we were sent the wrong part (an op-amp I think) and couldn't wait for the right one to be sent so we had to design a work around and write up instructions for the fix which involved soldering a tantalum capacitor to the underside of the board. Stuff like that happened all the time.

[suverman]

Thanks a lot guys, last thing, do I replace all the caps in the system? And if caps are indeed the problem, shouldn't the problem recur, instead of being random? From what I have observed, on an average 1 out of 5 attempts successfully boots up the game and the console continues running. This I have noted for around 1 month back I acquired the console.

[ApolloBoy]

Thanks a lot guys, last thing, do I replace all the caps in the system?
Make notes of the ratings on all the caps to start out with. Make sure to match the capacitance rating (which will be in uF) but you can higher on the voltage. Replacing them is fairly easy, the best way is to clip the old ones out and use your soldering iron to pull out the legs. Then you can use a desoldering tool to clear out the remaining solder, and just stick the new ones in while making sure to mind the polarity (you don't want to mix up the leads on caps!).