Saturn PSU repair, need help.

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10-19-2018, 11:22 AM
strider1911

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Saturn PSU repair, need help.

Hello.

I have a Jap Saturn with a blown power unit. At first I thought it was just the fuse, after replacing it I found out the console blows the fuse instantly when power is introduced.
Upon closer inspection I realized that at least 2 components are damaged, but I can't tell exactly what they are:

Attachment 14480

(picture is of another power supply with the same "Type A")

I couldn't find schematic for it anywhere. Here is what I don't know:

1. YELLOW - There is a strip of components at the bottom (resistors? capacitors?) with a burn mark. Do you know what it is?
2. GREEN - A blown resistor, the damage made it impossible to read the color codes. Does anyone know what value is it?
3. The varistor looks fine.
4. Logic dictates there might be some hidden damage, so I'm open to suggestions.

Thanks in advance, any help is welcomed.
10-19-2018, 03:54 PM
Raijin Z

YELLOW is usually resistors. My question is, what voltage are you feeding it? While Japanese domestic voltage is 100V AC, and US is 120V AC, that 20% difference isn't normally enough to let the magic smoke out of most electronics. The board seems to be behaving like it's being tremendously overvolted, blowing out resistors and fuses.
10-19-2018, 06:19 PM
zyrobs

Those boards are rated 100-120VAC so using US power is not a problem.
Please try to post a pic of the actual part that gives you problem, so we can see if it indeed has an issue or not. Sometimes people mistake things, like calling a glued down crystal a leaking cap.

I'd check if the unit uses those dodgy TOP PWMs or not, they are known to cause issues.
10-19-2018, 07:36 PM
strider1911

Quote:

Originally Posted by Raijin Z

YELLOW is usually resistors. My question is, what voltage are you feeding it? While Japanese domestic voltage is 100V AC, and US is 120V AC, that 20% difference isn't normally enough to let the magic smoke out of most electronics. The board seems to be behaving like it's being tremendously overvolted, blowing out resistors and fuses.

I believe the original owner fed it 220v. I feed it 110.

Quote:

Originally Posted by zyrobs

Those boards are rated 100-120VAC so using US power is not a problem.
Please try to post a pic of the actual part that gives you problem, so we can see if it indeed has an issue or not. Sometimes people mistake things, like calling a glued down crystal a leaking cap.

I'd check if the unit uses those dodgy TOP PWMs or not, they are known to cause issues.

The 2 components I marked are damaged for sure, the resistor strip has a burn hole straight through it, like someone used a magnifying class to burn it. The resistor is completely burned as well, looks like burned coal. I would've taken a photo but I don't have a camera that can do macro shots at the moment.

By PWMs I assume you mean the regulators?
10-19-2018, 07:45 PM
strider1911

Update:
I checked the resistor array (YELLOW) using a multimeter, unfortunately it seems to have custom value for each resistor in line (the resistance of the blown one being infinite) so I can tell which value should the burned one have.

Update 2:
Just noticed the resistor array has a writing on it: "4922 YAMAHA".
10-19-2018, 08:01 PM
zyrobs

If it was fed 220V, then the varistor would've blown and the PSU would most likely wouldn't have other issues (I've blown a few). It probably has another failed component.

The PWM chip is the one labelled TOP102YAI. They frequently cause issues. But if you have other components having holes burned in them, it's probably too late to fix it and you should look for a replacement instead.
10-19-2018, 08:18 PM
EyeDeeNo76

Here's another approach (when they get them) replace and install all new but would need to get a 12V 2A power supply adapter too.

SaturnPSU

https://www.retropsu.com/store/wp-co...ll-416x416.jpg

Description

The SaturnPSU is a simple, fast to install replacement power supply for the SEGA Saturn that not only reduces heat inside your console from the original power supply, which can help extend the life of your Saturn, but also frees up internal space for any other mods you may have or want to install. It is also fully compatible with the Rhea and Phoebe as well as the original Sega Saturn disc drive.

Features

Small Size, Just 45mm x 50mm (1.77in x 1.96in).
Works with all known power supply variants, Type A, B, & C.
Works with Sega Saturn’s from all regions.
Drop in, easy to use replacement for original power supply (no console mod necessary).
Utilizes your original Saturn power button.
Runs from an external 12v 2+ amp power supply (not included).
More space inside your Saturn for other mods. 12v and 5v power headers available for mods.
10-21-2018, 10:15 AM
pyroesp

50$ for a simple power supply like that is expensive.
Get yourself a couple DC-DC converters from aliexpress and power it from a good 12VDC power supply. That should do it.
10-21-2018, 12:34 PM
Raijin Z

Would this function as a suitable replacement?

https://www.ebay.com/itm/163071752085
10-21-2018, 12:45 PM
zyrobs

That's a Dreamcast power supply.
10-21-2018, 04:06 PM
pyroesp

If you don't want to use dc dc converters you could use 78xx voltage regulators, but dc dc converters are more efficient.
10-21-2018, 05:12 PM
Raijin Z

I think the seller may just be an idiot.
10-22-2018, 12:26 AM
strider1911

1 Attachment(s)

Quote:

Originally Posted by pyroesp

50$ for a simple power supply like that is expensive.
Get yourself a couple DC-DC converters from aliexpress and power it from a good 12VDC power supply. That should do it.

You know what? I think I'll try it. Would a couple of these do for 3.3v and 5v?
https://www.ebay.com/itm/LM2596-DC-D...bsaJ:rk:7:pf:0

I know the 3.3v uses less than 2A because it is fused. Anyone knows how much current the 5v line uses?

I have a 9.3V 4A PSU I can use. Should be enough for all 3 power lines. I can remove all of the components from the original PSU and use it as a board.

Thanks everyone for your help!

EDIT: This is what I had in mind, will it work?

Attachment 14488
10-22-2018, 05:41 PM
pyroesp

I'd suggest you keep the fuses if there are on the original PSU, just for added protection.

Yes those are fine, I have a couple of those and they're ok, altough I'm not sure they can deliver 3A.
Also, those are adjustable DC DC converters, you might want to add a drop of your preferred glue on top of the potentiometer, just in case.

Measure the output prior to connecting it to the Saturn, make sure the voltages are correct and stable.
Also measure the voltage after connecting to the Saturn, just to check if the Saturn isn't pulling the voltage down due to too much load.

Hopefully the CD player is fine.
Happy gaming.

EDIT:
Make sure the correct voltage is connected to the correct wire too !!
I don't own a Saturn so you might want to wait for someone to confirm the connections in your diagram.
10-23-2018, 03:11 AM
strider1911

Quote:

Originally Posted by pyroesp

I'd suggest you keep the fuses if there are on the original PSU, just for added protection.

I can only keep one since the other "main" one is AC.

Quote:

Originally Posted by pyroesp

Yes those are fine, I have a couple of those and they're ok, altough I'm not sure they can deliver 3A.
Also, those are adjustable DC DC converters, you might want to add a drop of your preferred glue on top of the potentiometer, just in case.

Good idea, how do you know the console used 3A of each voltage?

Quote:

Originally Posted by pyroesp

Make sure the correct voltage is connected to the correct wire too !!

I have another type of PSU where the voltages are labeled on the board so that isn't a problem.

Quote:

Originally Posted by pyroesp

Also measure the voltage after connecting to the Saturn, just to check if the Saturn isn't pulling the voltage down due to too much load.

Good idea.

EDIT:
Thanks for the help!
10-23-2018, 04:45 AM
pyroesp

Quote:

Originally Posted by strider1911

Good idea, how do you know the console used 3A of each voltage?

I'm just doubting that those small DC DC converters can actually deliver 3A continuously.
I don't know how much current the Saturn uses.
10-23-2018, 12:00 PM
Raijin Z

The Saturn says it's a 25W device, but it seems odd that it would use nearly five Amps. Of course, I = P/E isn't the best way to determine actual current draw, as it's at best, a back of the envelope calculation.
10-23-2018, 03:33 PM
zyrobs

The few original power supplies that list amperage all say 0.35A or 0.4A, so I doubt you'd need ten times as much.
10-23-2018, 04:56 PM
strider1911

The 3V lead if fused so I don't have to worry about it, I can measure the current in the 5V line and shut the power off if it used more than 2A. Or I can add another fuse.
10-23-2018, 06:32 PM
Moirai

I think i’ll just recap my existing saturn PSU rather than replacing it with a new one
11-04-2018, 06:32 AM
majinga

Yesterday I was doing some tests with my Saturn and this is what I got:

9V 0,45A (average on read, but it jump up to 0.88A some times)
5V 1.3A (mostly stable)
3.3V 0.13A (jump from 100 to 130 mA)

This is a model 1 PAL, MK-80200-50. This unit use the 9V for drive the CD, this is why the current on the 9V rail sometimes go so high.
I'm bit rusty with Saturns, but, if I remember correctly some model 2 don't use the 9V to drive the CD. So on these units, the current consumption on the 5V rail can be higher.

About the resistor network, I suggest to desolder it before. The measures taken on the circuit are not reliable.
11-04-2018, 10:09 AM
strider1911

Quote:

Originally Posted by majinga

Yesterday I was doing some tests with my Saturn and this is what I got:

9V 0,45A (average on read, but it jump up to 0.88A some times)
5V 1.3A (mostly stable)
3.3V 0.13A (jump from 100 to 130 mA)

This is a model 1 PAL, MK-80200-50. This unit use the 9V for drive the CD, this is why the current on the 9V rail sometimes go so high.
I'm bit rusty with Saturns, but, if I remember correctly some model 2 don't use the 9V to drive the CD. So on these units, the current consumption on the 5V rail can be higher.

About the resistor network, I suggest to desolder it before. The measures taken on the circuit are not reliable.

Thanks! Exactly what I needed.