Hi, I have two Virtual Boys. One looks great while the other’s display is too bright. The mid-tones are blown out. For example, on Mario Clash, the title screen Mario and shell guy are almost one color.

I have played with the software brightness, but it doesn’t make the mid-tones darker relative to the bright tones. The same brightness setting looks great on my other VB.

It seems like a hardware issue, is there a known cause for this?

Thanks!

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I checked the voltage on the U8 voltage regulator, thinking maybe it was overvolting the LEDs. The voltage on U8 is the same on both VBs – 9v on the left side and 4.8v on the right side.

The blown-out displays work fine when swapped to the other machine, so it is something with the rest of the VB’s hardware.

Have they been soldered? If not, that’s the most likely fix.
It sounds like pin 18 (CLKB) of one of the displays is not making good contact, or that it is getting shorted to a neighboring pin (CLKA or CLKC). These three signals control the overall brightness in a kind of PWM fashion.
It’s pretty easy for the thin, foil-like “wires” in the display cables to shift around or fold up when you plug them in. The pins also lose their tension over time. I’ve heard of people adding some tape to the stiffener on the back of the cable to make it fit more snugly in the connector. You can also try pulling it out just a bit after pushing it in all the way, so the pin has a fresh area of cable to clamp on to.
If it’s neither a connector nor wire issue, then it may, unfortunately, be the output pin of the display driver chip malfunctioning.