botched megadrive mod

[moonwhistle]

I started on modding a PAL megadrive 1 for 60hz today. I cut the JP3 trace as shown here:

http://farm4.static.flickr.com/3128/2774264953_0a4420e4a1_o.jpg

At first the picture would keep jumping on and off but it was 60hz and settled eventually. Assuming the trace wasn't cut all the way through I cut at it again.

Now I'm getting no picture at all through RGB or RF. It will switch to a black screen in RF but that's it. The power light is coming on.

I'm assuming I've either blown something when touching the board or cut too far around the trace.

Is there anything I can do to salvage the console? I have the use of a multimeter if that would be any use.

Also, an unrelated question. My Megadrive 2 makes a loud buzzing sound through RGB on the boot screen and any game section with no sound. I bought the RGB cable off eBay and it's unofficial. I even sent it back for a replacement and the new one does the same thing.

I've read about a cable mod here:

http://www.retrocorner.net/index.php?Mods_%2F_repairs:Megadrive_2_RGB_cable_modification

Does this apply to unofficial cables? The one I bought was unofficial and custom made, the guy who made it seemed very knowledgeable.

Any tips would be much appreciated.

Thanks.

[speedlolita]

Doesn't look like you've gone too deep..

If you need a replacement I can do one for postage cost though.

Could try connecting J3 with a paperclip or something.

[moonwhistle]

Doesn't look like you've gone too deep..

If you need a replacement I can do one for postage cost though.

Could try connecting J3 with a paperclip or something.

That photo was from the guide I was following, not of my work. I may have cut further but I thought I couldn't go too far as all that's down there is the trace I want cut. I could take a photo of my one if that would help?

I did try bridging the cut trace with a paper clip but it didn't do anything.

Thanks alot for the kind offer, I may well take you up on that. I'm now worried about doing the same thing to another console though.

I find it odd as this is supposed to be the easier MD mod. I managed to complete the same mod on the MD2 despite making a pigs ear of the soldering.

[egparadigm]

I think frying the circuitry is unlikely. What is it, like 5v?

[moonwhistle]

I think frying the circuitry is unlikely. What is it, like 5v?

It's 10V.

[randombs]

Did you use a knife? If so, did it slip, maybe, and slit one of those nearby traces(assuming your board is identical to the photo)?

I'd also recommend checking just what JP3 is doing right now. According to mmmonkey's switchless mod guide, JP2 and 3 are meant to go to GND for English+50Hz mode(default PAL). I'm not sure whether it lets you run in JP 50Hz mode but, if not, maybe that's what it's currently configured as and could be causing your issue. I'd say chop both JP2 and JP3, check the continuity to ensure they're definitely not grounded anymore, and reground them both to another GND point(e.g. if your board is like the one in the photo, it'd be the left point on JP3). If you're convinced that JP2 is undamaged, you could just do JP3 and see.

You could try connecting the other side of JP3 to another ground wire and see or follow the trace and figure out what chip/leg JP3 is actually connected to and try joining that leg to GND instead. Also, do the same for JP2, making sure you won't go shorting any by connecting to both 5v to ground.

On a side note, I use a lino cutter for PCB traces:



It works a treat as it scoops, and makes light work of the traces - one or two scoops and you're done. It's also not particularly sharp so if you do slip, it won't take everything with it if you're gentle. I've never enjoyed cutting traces with a knife.

[moonwhistle]

Did you use a knife? If so, did it slip, maybe, and slit one of those nearby traces(assuming your board is identical to the photo)?

I'd also recommend checking just what JP3 is doing right now. According to mmmonkey's switchless mod guide, JP2 and 3 are meant to go to GND for English+50Hz mode(default PAL). I'm not sure whether it lets you run in JP 50Hz mode but, if not, maybe that's what it's currently configured as and could be causing your issue. I'd say chop both JP2 and JP3, check the continuity to ensure they're definitely not grounded anymore, and reground them both to another GND point(e.g. if your board is like the one in the photo, it'd be the left point on JP3). If you're convinced that JP2 is undamaged, you could just do JP3 and see.

You could try connecting the other side of JP3 to another ground wire and see or follow the trace and figure out what chip/leg JP3 is actually connected to and try joining that leg to GND instead. Also, do the same for JP2, making sure you won't go shorting any by connecting to both 5v to ground.

On a side note, I use a lino cutter for PCB traces:



It works a treat as it scoops, and makes light work of the traces - one or two scoops and you're done. It's also not particularly sharp so if you do slip, it won't take everything with it if you're gentle. I've never enjoyed cutting traces with a knife.

Thanks alot for the advice. I used a scalpel to cut it. I'm afraid I'm a total soldering novice and this is only my second job. I've taken a picture as best I could of the cut trace, it can be zoomed to some extent for detail.

http://i720.photobucket.com/albums/ww207/43744852/100_0775.jpg

I don't think I slipped with the blade. Considering how much effort it is to cut a single trace I assume it would be visually obvious if another trace was cut accidentally.

JP2 is intact and the console was running is 60hz english after I initially cut JP3. The picture was jumping so I went for another cut and now nothing but a black screen appears when powered on.

I know it would be easier to just get another MD1 but I'd like to figure this out so I can avoid it happening again.

[egparadigm]

Did you actually reconnect the two halves of the cut trace, as suggested above? That would tell you whether it was connected to the cut you made or alternately that you may have slipped or some other unrelated issue.

[moonwhistle]

Did you actually reconnect the two halves of the cut trace, as suggested above? That would tell you whether it was connected to the cut you made or alternately that you may have slipped or some other unrelated issue.

Yes, I held a paper clip accross the cut and it didnt have any effect. Should I try soldering a wire across instead? Also, can I test the surrounding traces with a multimeter to make sure nothing else is cut?

[randombs]

can I test the surrounding traces with a multimeter to make sure nothing else is cut?

You can, but you'd need to find the ends of each trace to connect the multimeter to. A quicker, albeit gung-ho, method would be to scrape away the green lacquer from your chosen trace, roughly a few cm either side of the general area of devastation, and touch the multimeter pins on those.

[randombs]

Sorry, just noticed you replied to my post, so here goes...

Looking at your photo, the area seems fine. I'm leaning towards the cut being too deep but I'm not sure how deep it would have to be to muller a trace on the other side of the PCB as it depends on how thick the layers are and how many layers they used in the first place. I think there's some copper revealed in the thin trace joined to JP3:



It could be a trick of the light but I'd test that if I were you. Just scrape some of the lacquer off at the little hole at the left end of the red line. Connect the multimeter to that and to pin 26 on the chip at the top of the pic and see if there's a connection.

As for soldering a wire, when I want to quickly/temporarily test a jumper or similar, I scrunch up a small piece of tinfoil and tape it over. As long as it's scrunched up and not folded neatly, the pressure from the tape will pretty much guarantee a connection.

[mmmonkey]

It's ALIVE!!!!

for the benefit of someone else coming along doing a search....

The wire that goes through one of Ferrite Beads on the board had come loose


(That's it repaired)

Cheers
Pete

[randombs]

Yeah! I can see why there was such a draw for Dr. Frankenstein. Bringing dead things to life is super fun