Nicoya's Never-updated Blog: A Polarizing Subject

So I recently picked up a Boss SE-70. This is not to be confused with the Boss SE-50 that I already purchased a little while ago, although put a bookmark in that, we'll get back to it in a moment.

The unit was sold "for parts or repair" due to a nonfunctional display. Turning it on, we can see that indeed it is nonfunctional.

I had assumed that the likely cause was that the battery had gone dead and the contrast settings had got messed up. Then, without the display to be able to navigate back to the contrast setting, well, you can see the problem. Or not see it, as the case may be.

As I suspected, I was able to find an angle where the text on the screen was just barely visible.

However, navigating to the contrast settings and changing the value, while it did affect the contrast somewhat, did not fix the display. It just went from almost blank to entirely blank. I did some diagnosis and found that all the signaling, including the contrast voltage, were correct, so it was in fact a dead display.

It does have a nice bright backlight, though, so it's got that going for it. What doesn't have a nice bright backlight is my SE-50.

Switching the SE-50 on reveals a screen with a very sharp, high contrast display, but a pitifully dim backlight that's barely brighter than when it's completely turned off.

This of course means that I have one display with a good backlight, and one display with a good LCD panel. I think we both know where this is going.

While the newer display in the SE-70 has a clone chip, the one from the SE-50 has an original Hitachi HD44780 LCD controller.

Which isn't really relevant here, I just thought it was neat.

Anyway, to swap the backlight we first need to desolder the power leads.

It would be nice if the backlight would slide right out, but it's still stuck under the metal bezel. We'll need to twist the tabs on the backside and lift it off. Note that it also holds the LCD panel itself to the zebra strips, though after a while they tend to become fully adhered to both the LCD and the PCB, so there's not too much danger of knocking them loose. If you do, though, just put them back in place and they'll work just fine.

We'll need to do the same disassembly on the SE-70's display to get the good backlight out.

It was at this point I noticed that the bezel on the SE-70 display was also in better shape than the SE-50's bezel, particularly regarding the part where it wasn't covered with the decayed gunk of what was once some black foam. Instead it was covered with actual black foam. So I took both the backlight and the bezel from this unit to combine into the final working unit.

And speaking of combining things, the backlight looks pretty good behind the SE-50's display. And with the bezel on and connected to the SE-70, things are looking mighty fine indeed!

And it still works on the SE-50 too.

The SE-70's display is definitely toast. It's vaguely possible that only the polarizer is destroyed, but a whole new display is only about $3 which is less than a sheet of polarizer film, so I'm just going to go that route.