Sega TeraDrive PSU Repair - Trinity! Help!

I think the last four numbers on the TeraDrive were the serial number, not many above 7000 I believe. Whether the Model 1, Model 2 and Model 3 all got their own serial numbers I doubt. But thanks! I am curious if the serial is somewhere in between my working PSU and my faulty one! ;-)

Also I've received all the capacitors and the 2SB1274 / B1274 (Q2). Still waiting on C3331 (Q3) and M5237L (IC2). They were all ordered from the same place... obviously they've never heard of combined shipping... might all turn up tomorrow then I'll fire up the old soldering iron and desolder gun and get to work!

 

Here's an update, replaced all the caps. 6800uF and 3300uF were leaking bad - Sanyo branded. However, the buzzing speaker fault still persists. I'm still waiting on Q3 and IC2 to arrive and probably won't try installing Q2 until they all turn up.

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 10.80V
5V rail (red cables) - no load 5.02V
12V rail (yellow cable) - under load 12.12V
5V rail (red cables) - under load 4.75 - 4.84V

Any ideas short of replacing the parts that are already on order?

That said, with @DeChief and @Ronnie all having their nice 240V PSUs, I might end up going that route eventually. I dislike having 110V things in this 240V household. I'm now doing this for the sake of doing this than anything else. Any hints or tips? I do have an oscilloscope on hand - but you'd need to tell me what to hit and press

 

For some reason I always wonder about the diodes "D5" and "D7", and what exactly is the encapsulated IC1?

Yep, you can see mine here: https://www.youtube.com Y5IfNGIp00 it even has -5V for those who love early sound blasters with OPL2's

 

Haha, it looks like yours stacks about as well as N64s

I've picked up a couple of Mean Well RD-65A to try jamming in, width-ways they are a match which is nice, plus they are enclosed. Not that I don't trust my handiwork, but I REALLY don't trust my handiwork on AC devices!

Certainly the PT-65B has the bonus negative rail which @Ronnie is using to death with his ISA cards - a great cause by the way! But you are going to need to 3D print a new case for your TeraDrive hahaha

I'll keep the power supplies intact until the replacements arrive, then I'll do some more troubleshooting and ID D5 / D7 on the faulty vs good PSU. Although the good PSU is probably on the brink of failure as well.

 

Slight correction: mine's a 120V PSU. I'm going to have to run transformers all the time in Australia anyway, so I may as well keep the voltage true to what it was originally.

 

That PSU look good and its quite small for being enclosed, seems to put a good amount of juice too. Like I said, they come in different flavors .

You'll be surprised. I have something in the making.

I just need abou 1MB more to be content, I think I'm going to build me one of these: https://www.lo-tech.co.uk/wiki/Lo-tech_1MB_RAM_Board

 

Ahhhh you're just saying that, voltage smoltage If you want the old PSUs (sans cabling and switch and... socket) I can put them aside for your triumphant return to Australia next year?

@Ronnie No, you can't be that insane! I can not wait. Not one bit! You tell us when you do that thing you are doing! 3.5MB? What are you greedy? When playing around with the RAM, did you factor in the onboard 512KB might be doing something weird or strange?

 

I dont want to say too much but is the most advanced engineering work I'll be doing for a while.

That's the thing, I always fear the unknown. At times I can tell there are addresses conflicts going and what not .

Do you think the Lo-tech 1MB will work ok along side the XT CF lite?

 

I'll be patient then and wait for something else crazy to come out!
Trial and error is half the fun, am I right?
Honestly I couldn't say, these older machines are a bit before my time - I was a 486-era kid growing up. However drop the folks at Vintage Computer a line, someone there must have played around with that card (or similar to it) with an IBM of some sort - failing that the best way to find out is to try (as always it seems!)

 

The Teradrive seems like my neverending project and now, yall's

True dat

 

Haha, half the fun I say! With a reliable PSU that's local, I might even set one of these up on my room. All I'd need would be say a Sega Keyboard... hmmm... Anyway, I guess we could try summoning @RetroSwim from beyond the forum

 

@DeChief - Oh and if you ever pull apart the TeraDrive again, see if you can snag the serial number off the motherboard on the right hand side of the board as you are facing the front of the machine. I'd be curious to know if it has the same or similar digits as the serial on the back (~6001).

 

Who in the what now?

The Lo-tech boards are designed to work alongside one another, I use the 1MB board and the ISA ROM card, together in my IBM 5150.

All you have to watch out for is (1) does the Teradrive have a built-in hard disk interface of some kind, and if so, will its resources conflict with the XT-CF (which uses 0x300h by default). And (2) make sure the ROM base address doesn't conflict with anything already in the system, like the VGA BIOS.

You can map out the IO space with something like MSD or Norton Sysinfo

WRT the RAM card, you control how much of the 1MB is enabled. For instance, on an IBM 5150, you have to disable the first 256KB, as the system already provides that. If the Teradrive has 512KB, just disable the first 512KB. You also want to disable anything over 640KB, as the 8088 uses that region for other stuff.

Edit: OK, so I just did some reading, and learned that the TeraDrive is actually a 286, and the base model has 640KB standard.

In that case, the Lo-tech 1MB board won't do anything much for you, as it is hard-wired to the "first" 1MB of RAM. If your TeraDrive *only* has 640KB, the 1MB board will allow you to load TSR's into the HMA, but it's no use beyond that.

I see from this thread ( http://assemblergames.com/l/threads/sega-teradrive-simms-ram-upgrade-help-needed.62782/ ) that you can already add 1MB SIMMs, so the 1MB lo-tech board is of no use in this system.

 

Thanks for the input @RetroSwim, most appreciated!

Now as far as the PSU itself is concerned, I finally received the final pieces I was waiting on (C3331 and M5237L) and threw them into the pile alongside B1274. The bad news, it didn't work. The good news, more fault was detected. It seems as though the power supply is having some issues getting enough juice through quick enough.

The non-funcitonal unit shows the below values, but I had at first thought that I had a no power situation - it was close. Leaving the PSU connected for around a minute allowed it to charge up and then push through insufficient power to do nothing. I did notice that the 12V rail with no load was jumping between 10.9x and 10.3x every few seconds, while the 5V rail remained steady.

1135 - Working (Reference)
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 10.93V
5V rail (red cables) - no load 4.93V
12V rail (yellow cable) - under load 12.12V
5V rail (red cables) - under load 4.75 - 4.84V

And with that, I am terminating the TeraDrive PSU repair. Not with a bang but a whimper. RIP in pieces. Any speculation on what the fault may have been caused by is welcomed. Especially if you say transformer. Transformer will get you a "like".



* Waits for Mean Well power supply to turn up *

 

Found this page:

https://translate.google.com/transl....ne.jp/~luckyboy/room.html&edit-text=&act=url

Looks like even in the best case scenario, he still only got 48KB of UMBs, and did so using the SIMM memory. He also uses an ISA EMS board, like the Lo-tech 2MB.

 

Near enough is MEAN WELL enough, that's what I've always said... somewhat? It's a Mean Well enclosed PSU with the enclosed bit removed... yes I know, I know... in the old PSU box with a few bits dremelled away. I'm getting really good at using that thing! Need to pickup some 240V wiring from the local hardware shop and it'll be wired up. Has it really been over a month since I last did anything on this? Geez... where does the time go?

 

Wait, did you order a different PSU to the one I did? Yours looks so much wider, and thus neater because it fills out the old PSU casing.

 

Yep, yours was too easy to fit so I picked one that had a very snug fit hoping it would fit - and it does a pretty good job! The Mean Well RD-65A I believe! No negative voltage rails on this one though, I'm not making a McStackerDrive... I wonder how @Ronnie goes?

 

Shane, sir... Have you checked the secondary circuitry? There's a loopback circuit which measures the output of the PSU, closing the loop in a sort of PWM control circuitry.
That involves a optocoupler and a TL431 IC to help detecting the voltage at the output. Any anomaly on that circuit will have a effect on the output. Also I suggest you test it with some sort of load instead of open. Like go to the store and buy some high watt resistor that puts something like 2 amp load on the 5V rail. Would be decent to test the psu if you made a dummy load for all the voltages (calculate it based on the rating advertised by the PSU on it's sticker...).

 

Hello kind scholar! I did test with some load on the PSU by running the PSU, as for where the original is now - only @RetroSwim can answer that. Hopefully this info might help those who still have their original TeraDrive PSUs though!