Hello, I have a sega wondermega RG M1 that's recently broken. The last time I used it everything was fine but recently I attempted to use it and the mega cd half of the console is not powering on and it is not outputting sound.
Fortunately it does still boot up to wondermega bios screen and output a signal to the TV. I have powered it on with a alternate power source. At first I plugged in its original brick which was probably a mistake. It was as off spec and outputting 18v.
https://imgur.com/gallery/JVLjmPd
Here's a pic of the bottom pcb. You can see some of the rgb mod done by the previous owner. A few of the parts have a little flux dried on them from the assembly.
https://imgur.com/gallery/4mDDRTf
https://imgur.com/gallery/U9QTxPG
I did notice some green fuzz on one leg of this resistor.
https://i.imgur.com/vNj99wV.jpeg
4.7k Ohm. The one used here is mini size.
Help repair sega wondermega model 1
Help repair sega wondermega model 1
Last edited by MattyP on Sat Oct 21, 2023 11:20 am, edited 2 times in total.
Re: Help repair sega wondermega model 1
Welp. No dice on the resistor. I replaced it. https://imgur.com/gallery/7WFDbPL
It's doing the same thing.
I got a really good lead though here. This guy has done quite a lot to figure out the RG M1. It seems the next thing I should look at is the power supply. I've been reading through what hes done.
https://twitter.com/A3rgan/status/14117 ... a-rg-m1%2F
I have a dilemma. I can go about replacing electronic components but I dont really have the expertise or special tools to diagnose some of these electronic components. So really l'd be taking shots in the dark at much of this stuff. I'm not even certain which IC voltage regulator has gone out or how to find it. I might do more harm than good with it.
Perhaps, I'll be contacting Simon on Twitter or someone like him who can repair the console for me. I'll log the progress of that repair here. If I cant fix it, someone else can!
It's doing the same thing.
I got a really good lead though here. This guy has done quite a lot to figure out the RG M1. It seems the next thing I should look at is the power supply. I've been reading through what hes done.
https://twitter.com/A3rgan/status/14117 ... a-rg-m1%2F
I have a dilemma. I can go about replacing electronic components but I dont really have the expertise or special tools to diagnose some of these electronic components. So really l'd be taking shots in the dark at much of this stuff. I'm not even certain which IC voltage regulator has gone out or how to find it. I might do more harm than good with it.
Perhaps, I'll be contacting Simon on Twitter or someone like him who can repair the console for me. I'll log the progress of that repair here. If I cant fix it, someone else can!
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NoAffinity
- Posts: 1081
- Joined: Mon May 07, 2018 5:27 pm
- Location: Escondido, CA, USA
Re: Help repair sega wondermega model 1
Do you have a multimeter? Check continuity from the power supply input (positive) and follow the circuit to the cd side.
Assuming you have good continuity, are there any fuses in the circuit? Sega cd's are notorious for blowing fuses and not working. Not sure if that's true for these units but might be some commonality there.
If you lose continuity anywhere along the path then theres a good starting point - repair with some jumper wire.
Beyond that, you would need a simple logic probe to go deeper. 1) checking components on the cd side to confirm they have proper power with your multimeter. 2) checking with the logic probe for activity occurring where it should.
These things usually (for me at least) start out seeming very daunting but end up being a simple fix with a little educated exploration.
Given the information provided and out of spec power supply, a blown fuse or burnt up voltage regulator near the power supply input seems the most likely culprits. The latter is assuming the vr on these things doesnt have a wide range that can tolerate the 18v, and the out of spec psu is also exceeding vr capabilities.
Assuming you have good continuity, are there any fuses in the circuit? Sega cd's are notorious for blowing fuses and not working. Not sure if that's true for these units but might be some commonality there.
If you lose continuity anywhere along the path then theres a good starting point - repair with some jumper wire.
Beyond that, you would need a simple logic probe to go deeper. 1) checking components on the cd side to confirm they have proper power with your multimeter. 2) checking with the logic probe for activity occurring where it should.
These things usually (for me at least) start out seeming very daunting but end up being a simple fix with a little educated exploration.
Given the information provided and out of spec power supply, a blown fuse or burnt up voltage regulator near the power supply input seems the most likely culprits. The latter is assuming the vr on these things doesnt have a wide range that can tolerate the 18v, and the out of spec psu is also exceeding vr capabilities.
Re: Help repair sega wondermega model 1
I do have a multimeter. Seeing as I didn't get any accepting replies from repair services, I have been going around and touching parts in the wondermega with it powered off.
Dissassembling the wondermega was a little unnerving at first. Theres quite a few ribbon cables and clipped in wires. After taking it apart a few times it becomes trivial.
I actually, just put it back together this morning. It is still in its same state of not outputting sound or powering on the mega cd side. Im using a variable output switching power supply from ebay to power it with 10v. Optionally, I also have a PS2 slim power adapter to use at 8.5v.
There is one more thing to note about this consoles original condition which I had left out earlier. I had noticed the sound seemed to be amiss on my cartidge games. When I listened to an audio track on sonic 2, it sounded like the audio channels were out of sync, as if one of the audio channels had some delay to it. Hearing that was peculiar. It stood out to me as a potential malfunction inside the console. Lately, it outputs no sound.
So while I was tinkering, I did look for shorts on the IC voltage regulators near the input power. That part is the SHARP PQ05RF1 as pointed out by Simon Lock (Aergan) on twitter. These have heatsinks. They didnt have any shorts as far as I could tell when I did a continuity test. I then found the SAYNO Sanyo B985 transistor, also mentioned by Aergan. This appears to be shorted when I try a continuity test with my multimeter!
So, Im going to order that transistor. I also ordered the sharp voltage regulators but I might not need those.
It will be pretty nice if Im able to repair the wonder mega by just by replacing a few parts that Aergan did to fix his.
I have not yet used the console while turned on and dissassembled with AV hooked up. I may need to set that up later. I'm a newbie at electroncis but I am beginning to understand that the console will not bite me, so im willing to take a crack it.
Dissassembling the wondermega was a little unnerving at first. Theres quite a few ribbon cables and clipped in wires. After taking it apart a few times it becomes trivial.
I actually, just put it back together this morning. It is still in its same state of not outputting sound or powering on the mega cd side. Im using a variable output switching power supply from ebay to power it with 10v. Optionally, I also have a PS2 slim power adapter to use at 8.5v.
There is one more thing to note about this consoles original condition which I had left out earlier. I had noticed the sound seemed to be amiss on my cartidge games. When I listened to an audio track on sonic 2, it sounded like the audio channels were out of sync, as if one of the audio channels had some delay to it. Hearing that was peculiar. It stood out to me as a potential malfunction inside the console. Lately, it outputs no sound.
So while I was tinkering, I did look for shorts on the IC voltage regulators near the input power. That part is the SHARP PQ05RF1 as pointed out by Simon Lock (Aergan) on twitter. These have heatsinks. They didnt have any shorts as far as I could tell when I did a continuity test. I then found the SAYNO Sanyo B985 transistor, also mentioned by Aergan. This appears to be shorted when I try a continuity test with my multimeter!
So, Im going to order that transistor. I also ordered the sharp voltage regulators but I might not need those.
It will be pretty nice if Im able to repair the wonder mega by just by replacing a few parts that Aergan did to fix his.
I have not yet used the console while turned on and dissassembled with AV hooked up. I may need to set that up later. I'm a newbie at electroncis but I am beginning to understand that the console will not bite me, so im willing to take a crack it.
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NoAffinity
- Posts: 1081
- Joined: Mon May 07, 2018 5:27 pm
- Location: Escondido, CA, USA
Re: Help repair sega wondermega model 1
Everybody's got to start somewhere. Those sound like good starting points.
I take pictures as I'm disassembling if I think I'm likely to forget where things reconnect or how they're oriented. But, yeah after a few disassembles/reassemblies you'll usually become familiar with the process. Then it's a matter of making sure you dont go too fast and mistakenly connect something incorrectly.
Good luck with it. Staying tuned for a successful outcome.
I take pictures as I'm disassembling if I think I'm likely to forget where things reconnect or how they're oriented. But, yeah after a few disassembles/reassemblies you'll usually become familiar with the process. Then it's a matter of making sure you dont go too fast and mistakenly connect something incorrectly.
Good luck with it. Staying tuned for a successful outcome.
Re: Help repair sega wondermega model 1
A bad transistor does indeed seem like a common problem with the Sega CD considering Console5 sells them, so hopefully replacing it fixes your Wondermega.
Re: Help repair sega wondermega model 1
Thanks! It will take some time before I get back to it. I work away from home but I'll be sure to post the progress here.
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DejahThoris
- Posts: 734
- Joined: Sat Oct 19, 2013 10:26 pm
- Location: Riverside, CA
Re: Help repair sega wondermega model 1
Looking at the datasheet for the voltage regulators they will handle up to 35v, so you wouldn't have killed them with the bad power supply.
That doesn't necessarily mean they're good, as they could be worn from old age or anything else, but the 18v would not have harmed them. It does seem a waste to purchase and replace them without just testing them with your multimeter while the system is running though. Pin 3 is ground, pin 1 is the voltage coming into the chip, and pin 2 is voltage going out. For all we know you may not even be getting voltage /to/ the VR at this point (which is why it's good to test).
That doesn't necessarily mean they're good, as they could be worn from old age or anything else, but the 18v would not have harmed them. It does seem a waste to purchase and replace them without just testing them with your multimeter while the system is running though. Pin 3 is ground, pin 1 is the voltage coming into the chip, and pin 2 is voltage going out. For all we know you may not even be getting voltage /to/ the VR at this point (which is why it's good to test).
Re: Help repair sega wondermega model 1
Yes, good point. I may have ordered replacement voltage regulators in error. I'll need to stop ordering more things on a whim to avoid unnecessary costs. a more calculated approach to part replacement is called for. I noticed a few swollen caps there too. Some of my parts are in so I'm looking forward to getting back to it.