Saturn Power Supply Failing - Repair Ideas?

I suppose these are the early kind from Yamaha with the ceramic hybrid module ?

An full re-cap is in order I suppose.

Edit : I meant full recap of the power supply unit.

 

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Not sure if someone mentioned here or elsewhere that it might relate to a particular voltage output on the power supply? For some reason I keep thinking its the +9v rail where the issue kicks in as the CD-ROM drive uses +9v.

My machine's an early model PAL Saturn (can't remember what model VA it is, but when region modding it the layout was definitely one of the earlier revisions). I think I have a mate with a dead CD-ROM Saturn that might have a working power supply, so might have to look into that as an option, assuming it has the same pinouts as my current one.

Still, a straight-out fix would be ideal. Less waste that way. Interesting that it affects NTSC machines, as I thought only PAL machine were affected (which made me think that the AC to DC process was struggling with 240v vs 110v).

And yes, gotta love those service bulletins! Such an amazing repository of info, shame that kind of info has been so tricky to get, but amazing that it's started happening!

 

CDROM doesnt use 9v

The 9v is only for scart switching and isnt in a NTSC console.

 

I am SURE the drive on all early Saturns, including the first model with 21 pin flat cable use 9v for the motor driver IC.

You're right if you're counting (some) of the Saturn consoles with the 4 pin power supply boards. These are 5V only.

Early units requite 3.3v for the SDRAM, 5V for the main logic and all processors and finally 9v for the CD-ROM drive motor driver IC.

 

The 4 pin consoles are 5 pin in pal land - 5th pin being 9v and only for AV switching via scart.

I was unaware that 9v is used elsewhere on older models though..

Edit:

Checked the VA0.5 schematics - you are indeed correct that 9v is present on the cdrom power connector for those very early models, though I dont see where it is actually used on any of the IC's. Interested to know when it stopped being needed. PAL consoles have 9v regardless, so NTSC consoles would be the easiest to tell.

 

I was going to fit a dreamcast psu but was to big.

 

All early 21 pin drives use the Matsushita DSP/ motor drive IC combo and the driver IC is the one which requires 9v. Later models switched to a different chipset which uses a Mitsubishi micro controller and a updated revision of the said Matsushita DSP/Motor Driver chipset.

Earliest drive (20 pin) uses 100% Hitachi chips... lol Also requires 9v.

 

The VA0.5 schematic has no 9v on the hitachi drive chips. Only 5v

 

I said that the chip which DRIVES the motors need 9v. It's a Matsushita chip.

Edit: I actually opened a Saturn to check and the driver chip is a ROHM BA6798S.

 

If thats what you meant,

isnt overly clear.

But either way, just saying I cant see it on the schematic. Though if thats the correct part number, then that datasheet shows it needs 6v+ which would be the 9v

 

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I had no idea about the <va6 difference.

Learn something new everyday.

 

If the +9v draw is a cause (or symptom?), that would explain the CD-ROM drive chucking a wobbly, but it seems unusual that the video output is angry... Or is that noise from a component on the PSU causing issues affecting the video encoder or leeching into the feed from the encoder to the AV socket?

Or maybe I'm going nuts and am not contributing to this discussion at all by espousing my crazy thoughts

Would be interesting to know if the problem is resolved by feeding a fresh series of voltages to the Saturn's pins from an external PSU. Though if PSU swapping works, my guess would be yes.

If caps aren't the cause, I wonder which parts are causing the grief.

 

Yep, PSU swapping fixes it so it has to be the PSU! :smile-new:
But a very good question, which component indeed. Anyone been poking around in their Saturns?
I've since moved along all my ones with the less-than-reliable power supplies.
In hindsight, I probably should have kept one to play with... :rolleyes-new:

 

So I'm bumping this thread as I've got a HST-3210 on the way that needs a UK PSU (or the fuse replaced in the JP one it has, is it that simple?) and also a HST-3220.

I had this ripple after playing my Saturn for a while before and thought the PSU was dying, though it seems now as if it is an issue generally. Luckily I had one of the later PSUs spare (from a Saturn I accidentally killed) which fitted fine and after a little testing proved to have no issues after playing for 30 minutes to an hour or so.

This is the good PSU: http://i.imgur.com/JfoMJE1.jpg

This is the bad PSU: http://i.imgur.com/8Mj6OQ2.jpg

I've just recreated the situation with all the screws removed and it proves to be the two transistors which are boiling hot and clearly malfunctioning. Could it be a poor board design that is causing them to overheat, or simply that the cooling isn't sufficient. In which case could you theoretically beef up the heatsink in order to dissipate heat better? Or perhaps simply find a more efficient transistor and replace the ones that are installed currently?

Lots of questions and assumptions but I'd like to be able to use this board.

Transistor markings are:

Good PSU - N5F F8P048 and J 9528 TOP202YAI PB0670
Bad PSU - FMB24L 56 01 and J 9525 TOP202YAI PB0550

EDIT: I just found on racketboy from this thread: Link.

Might be worth a shot.

 

Interesting considering there were no die shrinks on the hardware like modern consoles. Any voltage differences?

 

No, back then die shrinks did work differently. Back then the stuff would still work at 5v even after a die shrink. Saturn was still one generation behind the PlayStation on that part of it's design so it was using 5v parts mostly, with 3.3v SDRAM chips as memory. That's why it needs 5v and 3.3v.

The PlayStation was using 3.3v logic but it was still using EDORAM as memory ... lol

Die shrinks causing voltage reduction only started to make sense on videogames when the next generation (Dreamcast/PS2) came.

 

Thanks.

 

As mentioned previously by the French dude there are like 4 PSU revisions. Why, I do not know.

Either way I hope that cap placement solves this issue. That "fixed" board can go in my modded PAL one and I'll put the good one in my HST-3210.