Voyager Backlight Issue

[sinflrobot]

Hi,

I have a voyager that I purchase a few years back that I am finally getting around to getting installed. I've set it up on the test bench, and intermittently the screen backlight will stop working. If I shine a flashlight on the screen, I can vaguely see the image updating, but no light coming from the screen itself.

Anyone seen this before, have ideas on fixing, etc. My guess is that it is a bad ccfl driver, but wanted to see if anyone had gone down this road already before I open up a big can of worms.

[rainier]

I guess opening it up and having a look is the next step - if it is intermittent you can carefully tap around with the plastic back of a small screwdriver and see if you can find a break in a cable or something like that.

[rainier]

Also if it has not been operating for a few years as you say you should replace the CR2032 battery at the back - that is needed to store the backlight values and state. It might be going into night mode at a very low setting if it is starting up from random memory contents.

[sinflrobot]

Board with resistor in heat shrink

20201115_181756.jpg (111.92 KiB) Viewed 3371 times

I have opened the box up, and think I've got a good grasp of what is happening here. The CCFL inverter is a nice TDK unit that is no longer in production. It appears to be wired in an non-standard way bypassing pin header on the board, and directly soldering to the smt circuit pads. It looks like power is run to the power pins, plus hard soldered to the enable pin as well. The dimmer pwm has an inline 1.5k ohm resistor that essentially bypasses the 3k smt resistor that is on the board.

Circuit Details

20201116_185001.jpg (95.72 KiB) Viewed 3371 times

My first instinct is to see if the issue is in the wiring. I've found the proper connector for the board, so I am tempted to order that, desolder all the inline connections, and see if that fixes it. Rainer, do you see any gotchas with that? 3k vs 1.5k, etc.

If the wiring is not the issue, next up would be to replace the board. Unfortunatley all I see out there are cheap generics. I'm guessing any of them would work okay (as long as they had PWM dimming). So, I guess that would be my second attempt, if a rewire is still failing.

Other ideas?

[sinflrobot]

Update on this.

I have repaired the unit, and wired up a new connector that uses the board. I thought I'd post my findings here in case anyone else runs into this.

completedsmall.png (252.4 KiB) Viewed 3349 times

I purhased a wired connector for the board for about $10 after shipping from digikey. This allowed me to clean up the wiring, and salvage the inverter board.

For reference, the root cause of the failure was a bad solder joint on the resistor for the enable pin which was purposefully bridged from the 12v line. I removed the bridge and soldered in a new 10kOhm resistor. (that little bugger was tough!)

theFixSmall.png (228.48 KiB) Viewed 3349 times

After everything was wired up, display tested out good, with dimming functioning correctly as well.

[sinflrobot]

Here is the wiring diagram for the connector:

pinssmall.png (206.36 KiB) Viewed 3349 times

Of the 8 pins/wires only 5 are actually used. The pinout is as follows:
1- 12v
2- 12V
3- Ground
4- Ground
5- Enable (gets wired to 12V from Ribbon)
6- PWM Dimming
7- Resistor for Dimming (not used)
8- Alarm (not used)

ribbonsmall.png (180.63 KiB) Viewed 3349 times

On the MGL ribbon connector:
1(stripe)- 12V
2- 12V
3- PWM Dimmer
4- Ground
5- Ground

For me, I wired all 12 volt lines plus the enable line together in one connection, and both grounds into another. PWM dimming line was a single line.