Voltage Drop when console is powered on.

[bhopki14]

Hello,

I am repairing a vintage gaming console, Atari Jaguar to be specific. I have recently replaced the U38 Power Regulator (SOIC-16W package "Step-Up / Down / Inverting Switching Regulator" ), the smd can be found here. https://console5.com/store/mc34163dw-soic-16w-package-step-up-down-inverting-switching-regulator.html

It appears to be soldered well and in working order. When I test with the multimeter, I see the required 9.5v when the power adapter is plugged in AND the console is powered off. However, when the console is powered on voltage drops to 5.5v.

Normally I would think that something is shorting out, bad ground, bad solder, but the power adapter itself drops to 5.5v. Not just the components on the board. So I tested the power adapter on my second Atari Jaguar, and everything works fine. So I don't believe that the power adapter is the problem.

Do anybody have any idea what I could check/test out next? I'm at a lost.

Below is a link to a view of the motherboard.
https://upload.wikimedia.org/wikipedia/commons/thumb/3/33/Atari-Jaguar-Motherboard-Flat.jpg/1471px-Atari-Jaguar-Motherboard-Flat.jpg

[Inverted18650]

Hey mate, you will need to provide more info. What "power regulator" did you replace? Is it a "wall wart" or did you desolder and replace a voltage regulator IC, or power transistor? I do not work with Atari systems but a power rail, is a power rail, is a power rail. If the voltage "collapses" under load you could have a bad regulator or its under powered.

[DaJMasta]

Your power supply probably can't provide enough current to meet the needs of the system.  This can certainly be caused by bad parts or shorts, but it also could be as the previous poster mentioned and you've just swapped to one that isn't up to the task.


How much was the original adapter rated for, and how much is the current one rated for?

[james_s]

He says the power adapter works fine on one Jaguar and not on the other, so clearly the console that is causing the voltage to sag has a fault that is causing it to draw too much current.

[Armadillo]

Well, you got 2 of the same atari, just compare point to point ohms to ground, between the good one and the bad one starting from the adapter socket inwards.
That way, you can trace and locate point of low resistance or bad component.

[james_s]

Did you test the diode that goes with it? Also when a buck regulator fails the output frequently rises to the input voltage so it's not unlikely that every IC powered by that regulator has been fried.