Saturn PSU dead, need advice

So the other day, after playing for a few hours, I wanted to change games and it didn't power back on. It smelled like heated plastic. I removed the board, but nothing is burnt. It smelled more around the Ac line area. Could a component overheated and failed? Fuse is fine, switch going to the board works. I suspect something like the parts in the RC1 and C1 locations. How do I test them?

It's a US first generation model.

 

Do you have a voltmeter? There's a fuse on there, check it.

 

And regarding c1, without looking at a picture of the board it should be a capacitor. It's hardly worth testing them (equipment is expensive) and caps only have a limited life span, if you suspect a cap just replace it and go from there

 

yes I have, it's fine.

 

its likely the voltage regulator rc1. to test, you could measure the voltages but it maybe the quickest to simply replace all caps and also the voltage regulator. replace the regulator with something more modern and the psu will also get less hot in the future.

and you can also add this fix to improve the psu and avoid further problems:

 

That one is a big gray plastic box.

 

Got a good quality picture of the PSU?

Edit:
Nm someone posted above that I didn't see.
Does your PSU match that picture? I read your comment that it's first generation as it's a VA0. But you may have just meant model 1...

 

What is it called? is another voltage regulator? So you remove the resistor in the R34 location?

well, here's mine:

 

no, you just add a cap with 2200µF 10V at the marked position (green). make sure the polarity is as marked in the pic or you could fry the psu again .

but as said, replace the voltage regulator rc1 and all electrolytic caps. measure line voltages afterwards, and if you get whats needed, it should work again. c1 usually doesnt blows, if theres anything else gone its one of the varistors.

 

What's the specifications of this voltage regulator?

 

RC1 looks like a bridge rectifier to me. Not a regulator.

 

Ah yes! Thank you. Do you know the specifications of the part?

well tested the part as a bridge rectifier and it's fine... Caps are good. The only thing I don't know how to test is the gray box, I tested it as a capacitor and got nothing.

EUREKA! I think I founded the culprit! It's the varistor in VR1 location. It's the only one that gives me a resistance reading. Gonna change that and see what happens. I will only able to get the part in 2 weeks, I'm going on vacation. At least I know what's wrong.

BTW, what should I get as a replacement?

 

That's normal for the varistor.

The problematic component will most likely be the TOP102YAI, it is a three-leg PWM switch IC, marked as Q1 on the pcb. They are the most commonly failing parts in Saturn power supplies (not counting the fuse and varistors blowing up when people accidentally plug a 110v console into 220v mains).

 

How do I test it?

 

Someone posted a picture already.

 

Replace it, and if it now works, then that was the faulty component.

That's not his PSU, he posted a pic of his only later.

 

First, not his PSU.
Second, was posted while I was writing my reply and I even edited my post after to account for it.

 

There's no way to check if it is faulty or not? I do not have any spare parts, I have a JP Saturn, but I don't want to cannibalize parts from it. I'll be on the lookout for a broken Saturn that powers up.

 

At a guess I'd check if it properly gives off the +5vdc values when powered on, according to the schematic posted earlier in the thread.

 

i am sorry for the confusion with my pic post, i just "guessed" by my experience with saturns .

and yes, also mixed up the part from top view, rc1 should be a bridge rectifier then (also a new word for me, "brücken gleichrichter" in german).