Sega Mega 32X Video Flickering / Distortion

Just wondering if anyone on here has come across this type of issue before.



Model 1, Serial: 110040340 - Slight video distortion / flickering after 40 minutes uptime.
Model 1, Serial: 120007120 - Severe video distortion / flickering after 30 minutes uptime.
Model 1, Serial: 41e09193 - Doesn't seem to show any flickering of video distortion at all after 60+ minutes.

Zyrobs (from here) pointed out to me that the HUD in Doom is fine because it is rendered by the Mega Drive.
However, I am curious as to why this happens to different degrees on two of my Mega Drives but the issue is completely absent on one of them.
The above photo galleries have photos of all the internals of the Mega Drives, so if anyone spots anything that may cause this let me know! :biggrin-new:
Of course if anyone else can replicate this issue on their own Mega Drives / 32X that would be helpful as well.

I've tested across four different 32X units, so it does not seem to be the actual 32X units or I have really bad luck at finding working 32X units...
The serial number range on the 32X units is from 15107xxxx to 15108xxxx - not much variety there at all, probably because not that many were made.
I did have a poke around in one of the 32X units and cleaned the two ribbon cables as well as cartridge connector, no improvement though.
I've got power supplies running all over the place and changing those doesn't seem to make a difference either.

Anyone feel like chiming in?

 

So it happens in any combination of those three Megadrives and four 32xs?

Have you tried connecting them with a different cable?

 

IMHO it's due to failing caps inside the 32x in question

 

Wouldn't surprise me but with everyone going "bad cap" crazy I'd hesitate to simply jump to that conclusion. They should probably be replaced anyway at this point if anything to eliminate it as a possible future problem.

 

Happens in combination with two of the three Mega Drives and all four of the 32X units.
One of the Mega Drives shows no issues at all when connected up to any of the four 32X units.
I've tried different cables running to the Mega Drive and through to the TV with no change as well.

I find it very strange that it doesn't happen on one of the Mega Drives though.
I do have another unit with a similar serial range of the working one coming later this week.
So at the moment I'm pulling all the 32X units apart and checking their internals - so far so good.

I am planning on replacing the caps in at least one of them in the near future - likely the one I jam into a Mega Drive 2... but that is a while off yet.

Edit: Unless Mega Drive Caps perhaps...? Perhaps, perhaps, perhaps! Although the Mega Drives are burnt in pretty well and all run like the wind...

 

I've given the console I picked up last week beginning with the serial 40exxxxx and it shows the issue almost instantly.
So given the Mega Drives all show the issue at varying levels... I'll give a full capacitor replacement treatment to one of them and see how it goes.
Will report back the results unless I completely forget about this thread... if that is the case apologies in advance!

 

yeah it would be nice to know what happens, good luck with the repair!

 

Thanks! Looking forward to reporting back... Guess I'll need to get the caps first! Baby steps...
Anyone know if any of the electrolytic caps are worth swapping over to tantalums?

 

I'd just swap the ones at the video output part first because those are more likely to cause potential issues. Then again, most of the caps are there and on the headphone out or around the ym2612, if memory serves.

Also, try just putting a cap on the c-sync line... same process as that HDTV "fix" listed at mmonkeys site. If the 32x uses that signal for sync instead of splitting the composite video, then it should have some effect at the very least.

 

Actually replace all of them. The ones that go through the +5V are more important than they look like. Actually, if there's too much digital noise zapping on the power supply rail you risk having all sort of random problems.

So yes, replace all of them as soon as possible.


Only advantage tantalum gives over conventional electrolytic caps is size. The price tag on them make them only worthwhile on portable applications. So honestly, only put tantalum caps if your money grow on trees.

 

That sound logical.

 

In fact, poor/old/bad capacitors are usually affected by the temperature and they have a tendency to operate closer to the original characteristics when warmed up, which explain the problems of units that fail while cold but then start working after warming up a bit ...

 

Excellent, now I have a game plan. Time to get some orders placed.
Why did I have to pull apart the Aiwa Mega CD this weekend. Why are there so many things to get sidetracked by!
Thanks for your input guys, I'll be sure to post back with results.

 

Problem appears to have a solution thanks to the newly released manual by Omp and all who donated.
In service bulletin 008 and 012 found here it mentions that the VA4 Mega Drive doesn't like the 32X that much.
So much so, that they recommend both the 32X and Mega Drive be modified to prevent the shakes.
I guess even they don't seem to certain though, especially since there are two bulletins on it.
I'll give it a go when I have time, but no one else ever came across this?
At least we know you'd need a VA4 Mega Drive... Is there a list anywhere of the various revisions and where they were released?

 

Here is a good guide, mostly based on the American market though....

http://www.sega-16.com/forum/showth...-good-Genesis-1s-and-Genesis-2s-from-bad-ones

 

Excellent! I found this one here too.
What on earth does a VA3 board look like?
The earliest PAL boards I have are VA4 and I was under the impression they were launch units for Europe... not correct?

 

Sega was at the VA4 mark when the PAL launch happened, so that was most likely the PAL launch model. It wouldn't have made sense to make older board revisions, as the goal of new board revisions is to save cost and ease manufacturing.

It would be interesting if we could find a VA3 PAL model, but I don't think they ever existed, considering that I've seen pictures of mid-1990 VA4 japanese units, and the PAL launch was at the end of 1990.

 

It really does seem quite unlikely doesn't it!
Also I was playing around with the Mega-CD dev unit today, found it has a PAL mainboard in it - even though it has a Genesis top half.
The board only has "IC BD M5 PAL", would that indicate not VA4, but a later revision? VA6?
There's no EXT port present, so it seems to match what a VA6 would be.

Edit: AND what I was supposed to say is that the 32X had no issues at all!

 

It's a VA6, going by your pictures. Check the labels near IC4...

 

How did I not see that. Yep VA6, bright as day! :wink-new: