Sega TeraDrive PSU Repair - Trinity! Help!

Like Neo in the Matrix dodging bullets, I need your help! I've reached a point where I have some limited time to attempt repair of the Sega TeraDrive PSU but I am going to need the help of some of the more knowledgable folk than me. I know you're all on here... lurking!

*blows dust off notes*

One of the reasons I have two of everything was originally for solving this type of problem, unfortunately it only helps to a module level, not component. So I have two TeraDrives, a model 2 (dual floppies) and a model 3 (30MB WDL-330P hard drive with its hilarious edge connector and one floppy drive).

One produces a buzzing, clicking hum like noise through the internal speaker when powered on and does not POST at all. After a minimal configuration resulted in the same issue I started swapping core parts - starting with the PSU. Sure enough, it roared back to life.

So I've got a non-functional power supply with a serial ending in 0629 and a reference power supply with a serial ending in 1135. There's no physical anomalies (blown caps) that I can see with the naked eye but have a look at the photos down below to see if you can spot anything peculiar

1135 - Working
12V rail (yellow cable) - no load 11.46V
5V rail (red cables) - no load 5.00V
12V rail (yellow cable) - under load 12.16V
5V rail (red cables) - under load 5.17V

0629 - Non-functional
12V rail (yellow cable) - no load 11.14V
5V rail (red cables) - no load 4.93V
12V rail (yellow cable) - under load 10.73V
5V rail (red cables) - under load 3.10V

I welcome any suggestions on how to fire forward, I am very cautious when dealing with live voltages / currents, I don't want to be zapped. That's just no fun. Tools I have at hand are soldering iron, multimeter, and an oscilloscope. While I can solder and probe things with a multimeter I have no oscilloscope experience at all. It was on my to do list but then I enrolled in a programming course. Go figure, right?

I just wish I had more time to learn about troubleshooting on a component level. Sorry to have to always ask for help on here, you guys are great!

Anyway, here's a few starter photos to get anyone who wants (or can) help me narrow down the problem. If you want better photos of certain parts just say so, higher resolution? You name it, you got it! Poke this, poke that? I'll give it my best!

 

Actually a friend of mine is trying to fit in a picoPSU or some sort in my TeraDrive instead of repairing the original PSU. It's gonna be quite a journey, but i guess this is a better option than reviving the original PSU.

 

The thought has crossed my mind and I did attempt a similar thing with the Amstrad Mega PC, however someone said something about negative voltage rails as it was an AT-type PSU not ATX - is that the correct terminology? AT vs ATX? As for the TeraDrive I thought it might be something in the middle, worst case I could always head down that path - they are such tiny PSUs and having the power brick externally would be a positive, but a negative for keeping it as close to original parts as possible.

By all means do let us know how he goes! Have you got a thread lying about somewhere I can subscribe to?

 

To be honest i don't have that much knowledge about PSU's, i'll see what he comes up with. He knows what he's doing.

I don't care that much about original parts, i just don't want to rely on the original parts, i only care about getting this unit up and running again (and hopefully this will be a solution for other TeraDrive owners with a faulty PSU in the future).

Will definitely let you know how it will progress, but i think i'll let him post his findings when it works. As i said, i'm a total n00b when it comes to these type of repairs and rather let experts look at this and explain how to fix it

 

Thanks! and I guess that's why I'm here too, birds of a feather right?

I'm hoping to pass my TeraDrives onto another lucky soul since I don't have the storage space for them anymore sadly. Of course I'd like them to be as functional as they could be, not so much for profit but for preservation. Although I have noticed the two do go hand in hand!

Yep, completely understand on that last point! That's what I'd probably do too if I knew anyone! Although if there is someone locally... I should post a WTB thread as well asking for services! Thanks @MHG good thinking!

 

Haha yup, the TeraDrive combines two of my favorite things of my childhood... My Megadrive/Genesis and my PC. Having them in one unit is so nice. Too bad we never saw this in Europe, US or Australia

Still looking for the monitor and keyboard though, which seems a mission impossible too.

 

Ohhh don't worry we got the turbo charged officially licensed Amstrad Mega PC and Mega PC Plus! Mmmm discoloured beige...
If you find a keyboard (like @DeChief did) I will be very jealous, again!

 

some of those caps look a bit puffy

 

DeChief is hopefully gonna help me out getting that missing controller cover!

And LeHaM i really hoped it would only be a Ben Heck solution, but this stuff is more complicated than that haha

 

I can almost hear the clicky-clacking already...

 

If I can't isolate anything, I'll just recap it for the sake of it - you can count on that!

I was reading your post and thinking about snapping the port off mine, but then thought it might be better to repair it... maybe It's alright though, if I somehow manage to lose everything but the front bezel in a fire, there'll be no need for 3D printing a port cover

Never forget!

 

Could you post what's printed on IC2 (LV-Side)?

 

@Shane McRetro, your non-funtional PSU is definitely getting voltages below the specs. Try replacing capacitors C17 (3300UF) , C9 (47uf) and C16 (68000uf), this last one is a Nichicon VZ series that is quite common to go bad. As matter of fact, it totally leaked on my Teradrive power supply and I once also had a PC Engine Cd-rom 2 system that had all bad Nichicon VZ capacitors.

Not related to your problem but, do you have a pic of the glass fuse and its rating?

My power supply was beyond repair even though I tried replacing many components like the main 2SK723 (Q1) transistor. long story short the transformer is shoot on mine. There are many open frame power supplies that can be suitable to be used with the Teradrive that will also fit ok (inside the Tera PSU case) with just a little bit of wiring and imagination. These power supplies can have more than one output for example: +12V -12V, +5V even -5V. I have one of them as we speak and they are great. The one I currently have has -12V that helps with my sound blaster pro2 sound card since the Teradrive ISA slot doesn't have it at all, neither -5V (for earlier sound cards and what not).

For some reason I don't trust the pico PSU's (I remember the voltages fluctuating when tested). I tried something like this one (below link) and it worked good plus is small.

http://www.ebay.com/itm/Mean-Well-P...971268?hash=item1a02041384:g:A3EAAOSw9N1ViwCl

 

Thanks for looking! Looks to be an M5237L 0721 - that can't be a date code can it?

Thanks! Caps are a dime a dozen, might as well replace them all at the same time. Rule out as much as we can. Oh and Nichicon is my least favourite of the big capacitor brands... Rubycon, however, is my favourite closely followed by Panasonic / Matsushita.

Actually, I might as well list them all if I am going to start off there for any people from the future who stumble upon this thread.

Code:

===========================================================================
C6    330uF    200V    105°C    H=31mm    W=22mm    "Rubycon"
C7    4.7uF    350V    105°C    H=16mm    W=10mm
C9    47uF    50V    105°C    H=11mm    W=6mm
C12    1000uF    35V    105°C    H=22mm    W=12mm
C14    1000uF    16V    105°C    H=16mm    W=10mm
C16    6800uF    10V    105°C    H=37mm    W=12mm    "Nichicon VZ(M)"
C17    3300uF    10V    105°C    H=22mm    W=12mm    "Sanyo"
C19    10uF    50V    105°C    H=11mm    W=5mm
C21    10uF    50V    105°C    H=11mm    W=5mm

IC2    M5237L    TO-92L
Q1    2SK723
Q2    B1274
Q3    C3331
===========================================================================

Good news, the fuse matches the silkscreen, 3.15A 125V and has NEWSB on the fuse itself, brand perhaps?

*crosses fingers, please don't be a transformer*
I'll keep that eBay item watched in case everything falls through as another alternative. I suspect a lot of coin flipping will happen after this power supply bursts into flames!

 

Sometime ago in another forum, there was a guy asking for broken Genesis/Megadrive consoles. There was another member with a broken Teradrive (model 3 I believe) I think he was fed up with it because he couldn't do much with it being broken. He gave it away to him for free (only paid price of shipping) and as soon as he received it the only thing he had to do was to replace a couple of the PSU caps. Moral of the story? I don't know if there is one , but that fella sure got lucky.

Heya Shane! are you still in the process of loading all of your pic albums? I don't see the Teradrives .

 

If I'm taking this away right it's to replace all my caps, which I should know better than most Ordering them now, figured I'd recap a bunch of SNES / SFC units before selling them using my new Hakko tweezers - should be fun!

Ohhh yes, don't worry that's still on my list! I'm away from the house with decent internet and at 10MB a photo at say 80kB/sec up... it kills the entire internet connection here I actually thought of you while updating the page a few weeks ago - "This should be done sometime around July March 2017". I'll be quick than that though! Promise!

So TL;DR for now is ordering a bunch of caps and the Q parts and IC2 if I can find it somewhere - because why not, right?

Edit: Everything on order except for Q1 (2SK723) - ETA ~2 weeks, will update as we go!

 

Cool!, Let us know how it goes.

 

Well my TeraDrive has what I think is a similar problem, weird speaker noises (not as bad as @Shane McRetro's) and nothing on screen. The power LED doesn't even turn on.

I'm probably going to order a bunch of caps for my power supply too just to eliminate any chance of them being the problem. Make sure to keep us updated Shane! I can't wait to try Spear of Destiny on this thing.

 

Spear of Destiny! Save Mars! Wait... wrong game!

Edit: @DeChief What was the serial number on the top of your PSU? And the serial off the back of the unit?

 

The serial sticker on the back is partially torn, but the last 4 numbers are 6001. I closed the unit back up and can't be bothered to open it right now because I'm doing stuff, but I'll let you know the serial of the power supply next time I open it up.