Sega Saturn powers itself off

@ Druid II

You mean this ones a launch Saturn ?
How much PAL psu's revs. where there?

@ retro

By Outputs you mean on the secondary site the 3.3-5-9 Volts ?
There is 0V.

I can say, there is no hot component when the board shuts off.

The local repair shops know exactly the same as I do, when I would bring this psu to them, they wouldn't even know what it is or what to do with it xD

Ok ok, no V1 or V2 there is, Yoda says

Is there a available component listing for Saturn psu's with component informations?

I made my own schematic today with all components and could only measure the resistors and write down the readings on the caps and type/model numbers...

Still I don't know what the pot is for (RV201) and haven't found out over google...

 

The outputs of the PSU are what comes off the board via the cable, yes. If there's no voltage there, work your way back.. just be careful of the hot section. If there's nothing on this side of the transformer whatsoever, though, it's likely a transformer fault.

You might be able to use the service manual that was released, I can't remember what board revision it deals with... or whether it has the PSU diagram. If not, you might have to do a bit of reverse engineering.

Any television repair engineer worth their salt would be able to fix a PSU. It's basic electronics theory and if you don't know that, you have no business being inside a television. I'm not talking about a computer repair shop - you don't need to know anything about electronics to repair computers. A real engineer. Preferably someone who has been in the business 20 years or more. They'll know how to fault find a PSU.

There were three PSUs as far as I remember.

 

x

 

I think my multimeter was broken, cause it gave me weird readings.
I managed to get another multimeter and did the readings again.

This is what happend:
- 1-2 minutes 230 V primary / 3.3-5-9 V secondary
- after 2 minutes still 230V primary / voltage on every secondary line rises +2V, then drops to 0V and then on every line jumping voltage back and forth between -0.20 and +0.16V

EDIT:
today i did the readings on my own Saturn, the newer model (MK-80200A-50).

- psu sticked to the board and fired up, primary 230V / secondary 3.3 - 5 - 9V
- found out that the pot (RV201) is for fine adjusting the secondary outputs
- all components on the psu are exactly the same as on the older model psu (MK-80200-50)
- if the psu is not attached to the board when fired up, it behaves exactly the same as the broken psu after the shutdown and the voltage drop (like there would be no load) voltage on every line jumping back and forth between -0.20 and +0.16V

I searched the interweb for spare saturn psu's, but no luck. There aren't any spare parts to buy, not on ebay not on other marketplaces.

Has anyone of you got spare parts to sell ?

 

Did a recapping today and the Saturn ran just fine, until it shuts itself off again...it stayed on a little bit longer this time.
Again a buzzing sound before power off.

 

run it with the top case off, may give you a better indication of which component is buzzing, just put a little tape round the open/closed lid sensor

 

Did so, heard a little where it was coming from.
Did components with my working Saturn psu, found the error!

TOP202YAI is the component, maybe internal burned or something, cause I can't see any black smoke burning on the pcb or likewise.

Anyone has this spare part and willing to sell ?
Cause I don't want to buy from China...

Or is it possible to switch this component with a TOP224YN ???

 

x

 

Thanks for this suggestion!

Stupid me I already bought the TOP224YN and it's coming from the UK.
I can buy the TOP223YN from my country !

Now I see that:

- TOP202YAI has 30-50W
- TOP223YN has 50W
- TOP224YN has 75W

All other stats are exactly the same.
But I don't think the Power / Wattage would be the problem here.
The machine takes only as much power as it needs, so if it needs only 30-50W it will not take more.

And I dont test the psu sticked to the Saturn anymore.
I only test now with my multimeter if the correct voltages are on the secondary lines and if the psu stays on and won't shut itself off again.

 

x

 

Like I said, i switched one after another component from my working psu to the faulty psu.
And with this component switched, the psu starts directly up and keeps running.
I switch the old component in again, the psu won't do anything.
So yes, I am sure this is the faulty component.

I would meassure its input and output voltage, but as it is faulty, it won't give me any readings.

 

x

 

I think, if it's an overheating issue, then because the component is only screwed to the metal heatplate and there is nothing like thermal compound between them, so that the heat can transfer better. Just imagine a CPU with an attached heat sink, but no thermal compound in between...the heat would built up until damage...

I seen enough transistor ICs in subwoofers or power ampilifier, they have always thermal compound between heat sink and component !

But the most parts to take damage on PSUs are the caps, because the industry always uses el cheapo caps instead of good qualitiy low ESR. It's better to invest in good low ESR caps and solder those in, rather than have a faulty psu infact of el cheapo caps.

And a little site note:
I switched all caps too, but the hardest to get is the big cap 56μF 400V (meassures 18x22mm.)
They are only to get as snap-in and those won't fit.
I replaced mine with a 68μF 400V low ESR from Panasonic (meassures 20x32mm).
I always do my soldering jobs with my Zhongdi-912 soldering station, lead-containing solder and clean everything with 99% isopropyl alcohol.

 

I just wanted to reply to anyone who has this problem, it really was the component TOP202YAI that was causing this problem.
I replaced it with a TOP224YN and the Saturn keeps running from dusk till dawn and on and on.
The TOP224YN won't get as hot as TOP202YAI, it isn't even a little hot after hours of gaming

 

Excellent result and thanks for posting back, I've been watching this one!

 

x

 

Sure I wanted to report back to the fellows who helped me so much
Especially I hate it when searching the interweb for problems, get links to forum threads and never the solution is posted at the end.
Not in here, this is assemblergames !!!

@ Druid II
Let me know, im interested

 

I imagine the process of fixing a US Sega Saturn would be different, considering the different power requirements. But thanks for giving hope that these components can be fixed. You should write a guide for PAL reference so other people in the future won't have to go mad looking for something that is a PITA to find.

 

I don't think that US psu's are that different. You only have to look that the component you want to switch and isn't available anymore, the new one has the same stats. Like the only difference between TOP202YAI and TOP224YN was the wattage output max. original it was 30-50W and the new component has 75W. But that is somehow good, cause it doesn't need to work that much and will not get as hot as the old component.
Mhm, a tutorial...good idea. I could use some more tutorials on my homepage, too !

 

Well done to get it going again!