Sega Mega CD Model 2 Repair (Also Checking CD RF Level)

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This time a faulty Sega Mega CD! Nice simple fixes, very common!
#sega #megadrive #genesis #repair

[@GadgetUK164]

It goes without saying - the potentiometer positions may vary wildly depending on the drive and laser. I always show them because for the most part they tend to be in approximately the same position, and if one has been adjusted crazily by a previous owner that could stop the drive working when a good laser is fitted.

[@Hahnsoulo]

I've got a couple of Sega CDs with bad fuses that I'm about to replace. Did some research and found out that one thing that can cause the fuses to blow is if you leave the power cable plugged into the Genesis/Mega-Drive when you attach/detach it from the Sega CD/Mega CD. So basically, the 2 devices should only be connected/disconnected from each other when the power cables are unplugged and the power switch on the Genesis/Mega Drive is off. When someone is testing a Sega CD on a bench it's common to have to unplug it and plug it in over and over again from the Genesis as you are testing changes you are making to the unit. Some people probably get lazy, or just don't know any better, and leave the power cable in the Genesis when they do this and boom, fuse blown.

[@GadgetUK164]

Ah, yes - that would make sense!

[@Mymatevince]

Nice stress free fix there Chris and bonus footage of some scope work. Good job mate :-)

[@GadgetUK164]

Thanks Vince =D If I am honest I was gutted it was so simple - I really enjoy more complex repairs now lol! I know you're the same, you would be gutted to get a Nintendo Switch and find one component just fell off the board! (well, maybe you wouldn't because that would be a bargain pickup lol!!!!)

[@andrewlittleboy8532]

Glad this is a long video, lockdown starting to get boring now and you're one of the very few getting me through it!

[@GadgetUK164]

=D

[@FlashGordonMurr]

Man, I just love watching your videos. I learn so much from your repair videos! With shelter in place in the states here CT actually it's nice to watch some to help pass the time. Cheers and be safe, Flash.

[@GadgetUK164]

Thanks =D Stay safe Flash!

[@SionynJones]

Loved this gadget I was the guy asking about the megadrive during the live steam. Good to see you looking so healthy too after rubbish last year. Would be cool if you did a video explaining the rf level of optical drives. Stay safe!

[@GadgetUK164]

Thanks =D Might expand on the next drive I look at!

[@SkuldChan42]

I started repairing one of these - Sega-CD 2 (US model), and it doesn't have any work-around boards inside, the fuse was ok, but the rechargeable battery was leaking. I also found while removing all the caps to redo them is that there are some were pretty brutal to remove because of the massive groundplane, but hot air helped. Also thank you for figuring out the arf test point on this :).

[@Neffers_UK]

Oi, people. This guy has been doing live streams, and they have been uploaded. Please give them a watch if you are into this kinda stuff, cause you WILL find like minded people with their own channels that do this kinda stuff or demonstrate what they can do with the hardware they fix. This community is bloody awesome.

[@GadgetUK164]

Thanks mate =D Very good point - yes, so many great channels joining these streams!!!

[@GadgetUK164]

Stay safe (and the family!)!!

[@pandar11]

I dont mean any offence at all with this but you sound like Alan Partridge and its absolutely fucking brilliant to watch Alan Partridge fixing a Mega CD

[@GadgetUK164]

Haha =D I love Alan Partridge, so taking that as a positive =D

[@williamsquires3070]

Hi! Here’s a simple mod you can do. You’ll need a 390 ohm resistor, and a red/green dual-color LED (the kind with 2, not 3, leads). Once you’re done, replace the blown fuse, and remove the jumper from the side of the fuse that connects to the reverse-protection diode. Connect it instead to the green-anode/red-cathode of the LED. Connect the other side of the LED to the 390 ohm resistor, and solder the other end of the resistor (don’t forget some heat-shrink tubing) to the other side of the fuse. This assumes that end of the fuse connects to the cathode of the reverse-protection diode; if it connects to the anode, reverse the leads of the red/green LED. Now, with the fuse good, it shorts the LED/resistor, and they don’t light. If you plug in a barrel connector with the wrong polarity, the fuse will blow, and the red LED will light. If the fuse blows, but you have the correct polarity of barrel connector, the green LED will light. And, finally, if you plug in a barrel connector with AC, both the red and green LEDs will light to give yellow. Now you can drill a small hole in the back case near the barrel jack and hot-glue the LED so it shines through the hole. Now, if the fuse blows, the color of the LED will tell you what went wrong; red-wrong polarity, yellow-AC, and green-correct polarity with short (or perhaps a leaky filter cap in the power supply section.) HTH! 😎

[@GadgetUK164]

Nice idea there for reverse polarity protection - I like it ;)

[@SproutyPottedPlant]

I heard Krikzz is also working on a Mega CD cartridge 😀😀👍👍 I want to turn my Mega Drive into a monster! When I bought that Mega Drive I bought my ticket to ride. Better strap myself in having never played a Mega CD before.

[@GadgetUK164]

That's great news! Looking forward to that!!! =D

[@emmettturner9452]

Why these dudes fail is a very good question. Every Sega CD I've ever seen in the wild had a failed fuse. I had one since 2003 and finally replaced the fuse last year in anticipation of the Mega Sg launch. I replaced it with one that had half the rating (salvaged from a TG16) just so I could do a burn-in test before deciding whether or not it was worth ordering the right fuse. I left it looping through demos on the Sonic CD title screen during that burn-in test and around two hours later lightning hit the house directly! I was not using a surge suppressor. The music had stopped so I ran downstairs and found it on a black screen. After cycling the power it was perfectly fine. Remember: this is with a fuse that is HALF the rated capacity in a house that just took a direct lightning strike! The lightning killed a PS4 Pro, a TV, a box fan, an expensive router, an expensive cable modem, the home's HVAC system, and the EMP even killed my brother's car parked in the driveway... and yet the Sega CD that's already notorious for blown fuses barely had a hiccup and didn't blow even with half the rated fuse capacity. Whatever the explanation for Sega CD fuses blowing, I don't think it has anything to do with what people are doing outside the console.

[@GadgetUK164]

I suspect it probably relates to the Megadrive expansion connector - if the system moves slightly through vibration or something, or perhaps its moved a bit whilst it first powers on, maybe that causes an inrush or something. LOL @ yours surviving lightning when nothing else did lol

[@rfmerrill]

The reverse polarity protection is designed to blow the fuse on the sega CD model 2. Most consoles have a series diode on the input, but the sega CD has an antiparallel diode after the fuse.

[@aaronfifty5]

9 times out of 10, the fuses in these blow because people plug in an adapter that is over/under voltage or wrong polarity. NES AC adapter is the most common culprit. I've repaired many Model 1 revisions where the transistor gets fried by this as well. Unlike the Game Gear where it is almost always the capacitors, I've repaired dozens of SCDs and only had to replace caps maybe twice. Also those pico fuses are 💩

[@Ratchet_effect]

Chris you're a Diamond I used to repair Mega-drives and Snes for a video/game shop back in the 90s that used to hire them out, they'd come back broken a lot! May have told you in the past but my brains getting old and tired, I apologise if i did. Anyway as you can see different name, you have my real name in your Patreon credits. Steve Hawkins. long story short channel got removed due to DVD Selling Scalper web site saying they own the copyright to the VHS footage i used in a lot of uploads. 😢😒 I leave it up to you if you want to edit the name in the credits, But i will carry on to support you until the end, So no worries on that part. Stay safe keep up the awesome content.

[@GadgetUK164]

Thanks - will change it in the credits =D Sorry to hear you lost that channel =(

[@Brewskii2117]

About time you got an easy fix 13:23. :) (18:07 realizes you're not going to leave well enough alone!) :)

[@GadgetUK164]

Haha =D

[@xnonsuchx]

If I'm gonna unsolder one of those disc batteries, you can bet your ass I'm gonna put in a holder instead of another solder-in battery. ;-) I've only done it on synthesizers, though.

[@utubechannel8670]

me too

[@GadgetUK164]

Yes, a hold is a good idea - but I bet that battery lasts another 10 years now. A standard 2032 would be dead in a year or two - I dont want to have to keep going back in there.

[@conradlarsen3451]

Good to see some scope work. I also have a old analogue scope.

[@MrWaalkman]

Not to mention a venerable, old Fluke 77. Haven't seen one of those in years. :)

[@gam85191]

great video m8, do you know what that chip modification is for at 4:45? my one has it but i'm not sure what it is for

[@GadgetUK164]

I am honestly not sure! I would need to look at the schematics and service bulletins.

[@HuntersMoon78]

I've cleaned many lasers by pressing gently straight down on the lens and twist a cotton bud a few times. None of them have had any issue because they float on magnets.

[@garfieldepicmoments]

I believe the fuses fail on the Sega/Mega CDs because of a combination of the system being powered by a linear power supply and the fact that the system gets turned on by the Genesis/Mega Drive rather than by a power switch. This means that when there's a power surge, the linear power supply gives the system a higher voltage and unlike on normal systems, there no power switch between the power input and the fuse (so it'll blow the fuse even if the system is off).

[@GadgetUK164]

Thanks for the info! That does make sense!!!

[@diosyntaxa]

Interesting! Haven't had a Mega CD ever, but borrowed one from a friend back in the day. Just bought a package with an MD2 and a CD2 for that very friend (he got rid of it back when for some reason and now wanted one again). The MD2 has a problem though, AV glitches out now and then, quite often actually, so audio and video drops for 0,5-2s or so intermittently but the game keeps going so when it comes back Sonic (in this case) has moved. Probably some bad solder point making it glitch :) Meanwhile my MD1 does the job :D

[@diosyntaxa]

Update: It turns out it's a sync problem present in all PAL Mega Drives (MD 1 and MD2), and the reason I didn't notice it from my MD1 is because I was using an AV-Composite cable for that one. Found I could switch off auto sync for my Framemeister and there are cables that defeat the problem as well :) Cool, now I just need to get myself a Mega CD as well lol

[@TheCuddles87]

Sega CDs internal save battery are rechargeable 3V if I remember correctly. I know I used a ML2032 in mine.

[@SLRModShop]

45 minutes ? My Hobgoblin IPA and I are ready !

[@GadgetUK164]

Haha =D

[@StRoRo]

How long ago was this filmed? Thought you had a Mega SD. My friend gave me a "Broken" mega cd 2 from a job lot of retro gaming things. It too was just the fuse and internally was clean. Free mega cd

[@GadgetUK164]

Awesome!!! Yeah, not very exciting again this repair, but other than the battery, fuse and laser, they seldom fail it seems. Filmed in Sept / Oct last year!

[@TotalMoop]

Bit of an oversight Sega did with the Power Supplies for these and the 32X. Different Voltages for each device Would be nice to have a 3 in 1 PSU for this to supply the MD, CD & 32x all from one wallwart.

[@strra]

I think retrogamecave.com has one Edit: they're sold out

[@Sm0kingp0wer9]

Thank you for this amazing video! You did an excellent job explaining everything

[@GadgetUK164]

=D

[@wolvenar]

Back in the early 2ks my sega cd's fuse blew, I am not sure what did it. Anyhow i reolaced it then modded the Genesis and cd to feed power and the stereo audio from the potentiometer . I also removed the voltage reg from the Genesis and put a switching supply into the Genesis that could easily handle both. House power now plugs into the Genesis and I don't need to keep track of or find a place to plug in 2 wall warts. Nor worry about that audio cable.

[@CaptainKeelhaul]

Great video, thank you! I was wondering if you could give me some pointers. I've recently recapped my MCD2 (same mainboard revision). Everything works except for CDDA - it's a garbled mess (you can still hear hints of the main rhythm, though), both via the MD audio output and the RCA outputs on the MCD. I've checked continuity for all caps, which seems ok. Unfortunately, all I have is a multimeter for testing...

[@GadgetUK164]

Was it working OK before the recap? I would suspect a faulty opamp or something. Have you measured the voltage coming out of the voltage regulator there (the 3 pin device fitted to the heat sink)?

[@GadgetUK164]

Or a faulty DAC chip!

[@CaptainKeelhaul]

Thanks, I'll check, but everything was working before the recap.

[@CaptainKeelhaul]

OK I finally got around to work on the MCD again. The voltage regulator has a 9V input and a 5V output, so it looks ok. On at the RF test point in your video i get about 3.5V with a burned disc using a multimeter, which is way higher than what you had in the video. Am I doing something wrong?

[@AdamSommer70]

Great fix, thanks for posting.

[@SuperMoleRetro]

I have found it doesn't take much to blow that fuse. Why didn't you put a removable battery in place of the old soldered on one? Is there a reason not to do that?

[@GadgetUK164]

The main reason in this case is with a removable battery (eg. a normal CR2032), they typically last around a year (maybe 2 or 3 if you're lucky). I dont want to have to go back in there again soon! Plus, these rechargeable 2032 cells dont leak, so its not the end of the world if it fails eventually.

[@revengenerd1]

I had a problem with my Model 1, I think a part was missing as back in the day the Mega Drive kept coming lose and it eventually damaged the connector in the end my dad just soldered some wire to each connection so it worked but still it kept coming loose.

[@elpedromolina]

Hi, how are you?? Could you tell me the correct calibration for the laser of this sega cd model 2? I touched the potentiometer several times thinking that it was necessary to calibrate it, and it was not that, the problem was the transformer, it was not giving it the necessary amps for the laser to work, now the laser works but I want to put the necessary amps, the factory ones, let's say

[@GadgetUK164]

There are a few different variable resistors on there, I assume you only adjusted the one on the laser? You want to set it so the RF level is around 800mV and test with original and burned discs - if it works perfectly leave it at that level. if it's not perfect you can adjust up to around 1.1v, but somewhere nearer 800mV to 1v is better for the life of the laser.

[@Avaxx766]

We have this console and it starts up fine but when the Sega sign comes up and the little stars flash it freezes. It plays CDs ok though and we are using a 9v AC adaptor. Any ideas? Thanks 😊

[@GadgetUK164]

Sounds like possibly bad RAM? It could also be a dirty connection where it mates with the Megadrive? Alternatively, possibly a bad capacitor or something power related.

[@piplup2009]

Got a faulty mega cd about a month ago, replaced the fuse and doesn't work with an ebay 3rd party power supply (crappy cheap one) but ordered a mega drive 1 power supply since they're supposed to work for the sega cd so just got to wait and see

[@piplup2009]

EDIT: plugged the mega drive 1 power cable in and it's working :)

[@josephnealescratchcards]

great video as always

[@greenkoopa]

Do you have any ideas as to why I cant get the Model 2 working? It gets no power, has a new fuse and a good working (tested) power supply. I am very curious as to what it could be

[@GadgetUK164]

Maybe there's a short (check if anything is getting hot) - also measure the voltage going from the DC jack to the 7805 voltage regulator to make sure the DC is getting to it, and 5v is coming out.

[@greenkoopa]

@@GadgetUK164 yeah I've tried that. I've gotten more units in and I've been able to fix them just fine with power issues. I just use it for display now, the shell is in good shape

[@thepumpkingking8339]

So what did the factory bodge in this unit actually do? .

[@GadgetUK164]

I honestly cannot remember - I read about it a number of years ago, I think its probably a correction to a clock!

I'm trying to fix a MegaCD 2 which freezes on bios screen. I made a capkit. I've tried to switch the bios chip with a functional one but it does not work better. I have checked all the address and data tracks between the bios and the CPU, everything looks correct. I do not really know what to do anymore ... Do you have an idea?

[@GadgetUK164]

Try and boot one of the diagnostics carts for the system (eg. mode5.net/gendiag.html), or the 240p test suite ROM. You will need an Everdrive or similar flash cart to boot these. If those boot, it will allow testing of the different RAM types. I suspect if your issue is not corrosion or capacitor related, you may have a bad RAM on the Mega CD.

@@GadgetUK164 Very interesting ! Gen Test can test MegaCD rams ?

[@GadgetUK164]

@ It does it via the interface to the Mega CD side - bypassing the normal way it boots from its own BIOS. It may just help you work out whether the issue is with RAM (assuming it works at all). It could be faulty word RAM or something like that.

[@ShamanNoodles]

So this guy sold me a Sega CD that was supposed to be working on eBay. It's not.. Anyway, the motor doesn't spin at all. I've tried tons of stuff, the laser bobs just fine, and slides just fine. The laser doesn't prevent the motor from spinning. I'm afraid to just change the motor cuz idk if it's a random fuse or other thing... Any ideas man??

[@GadgetUK164]

The motor will only spin if it detects a disc. If can fail to detect a disc if the focus coils arent working (sounds like yours are, as it does bob up and down), or if the laser is too weak. Dirt inside the optical path of the laser can cause the reflecting laser to not be picked up properly - sometimes soaking the whole laser unit in IPA for an hour, then blow dry it off might work). If the laser is OK, it could be the BTL driver IC - the chip that drives the motor for disc rotation.

[@ShamanNoodles]

@@GadgetUK164 Thanks for response! I actually ended up figuring it out. I even made a little video on it for anyone else trying to troubleshoot. Under the lens, inside the laser assembly, is a little reddish rectangular crystal. That was unseated! I replaced the assembly and it works great now =)

[@jacktettero4507]

The Mega cd mis no screws its like that so is it made in the fabric

[@cloud1971]

Hello, could you repair my sega cd. I can't make it to spinn the discs :(. I replaced laser for a new one and even a drive motor but it wont go. I guess i have tweeked the potentiometers out of spec and now the console does not see the cds at all...

[@GadgetUK164]

Hi, sorry I cannot do customer repairs. I would suggest looking at the position of the pots in this video and re-adjusting yours inline with them.

[@jonnynolegs1970]

hi i have a mega cd2 2which wont power up its not the pico fuse can u fix it for me plz

[@GadgetUK164]

I cannot do customer repairs sorry =/ Check the voltage regulator - make sure 5v is coming out on pin 3. Be careful not to short the pins when measuring the 7805.

[@donpalmera]

I'm sure it doesn't hurt but using a multimeter to short something made me grimace.

[@GadgetUK164]

Haha - you raise a valid point there! In that one thing I didn't consider, is on some meters the current might blow the meter fuse. ie. my meter has a 0.5A current mode, or 10A. If I did that on the 0.5A range, the fuse may blow in the meter - IF the battery could provide 0.5A. What I wasn't doing here is shorting it out whilst powered up btw - just simply finding a quick way to short the battery contacts when powerless, in order to discharge the cap across it. I felt it was educational to show that when you measure current on a meter, that the contacts are pretty much shorted. It kills two birds with one stone. I've had people tell me they shorted out their supply rails before by trying to measure current that way lol.

[@donpalmera]

@@GadgetUK164 I've made the mistake of having my meter in current measurement, sticking across a power supply and popping the 10 quid fuse in there once or twice. Not saying what you did was wrong, I doubt much current flowed for very long, just gave me a flash back of "ah crap, there goes a tenner".

[@aaronfifty5]

Would love if any of these videos pointed out the pin for the RF signal. FYI- It's pin 2 on IC402. There's a test point marked "TP-RF".

[@GadgetUK164]

You mean like the point at 41:03 in this video...

[@r.a.w.talentart]

Love your sega videos, keep up the good work, also, check your twitter messages!

[@GadgetUK164]

Thanks =D Will sort it =D

[@dilanolvera7475]

I dont have a mega cd 1 and 2

[@beemac79]

Quick question :) I am new to all this but would like to fix my Mega CD 2. I picked it up from my Mums loft last month, who sadly passed away :( Anyway, powered it up, no red light. Two things I have done 1) Checked it isn't a faulty Power Supply with a inductance tester , it makes a noise therefore electricity. 2) Hovered the inductance tester over the Mega CD 2 (not opened as yet still cased), and it makes a noise. So, does that allude to it being a fuse?

[@GadgetUK164]

If there's no power light, it does sound like the fuse!

[@beemac79]

When you're checking for continuity, is the mega cd 2 plugged in?

[@GadgetUK164]

For the fuse - No!

[@beemac79]

Are you doing this for people mate?

[@GadgetUK164]

Sorry I cannot offer customer repairs!

[@beemac79]

@@GadgetUK164 Bloody Shame! Reckon I'll be able to do it?