perplx Posted May 19, 2010 Report Share Posted May 19, 2010 (edited) So I'm almost done with the sammichSID. It works, and sounds even better than I expected! Thanks Wilba, nILS, TK et al.! I just have a small problem: the LCD works, but the backlight doesn't turn on. I can only use it with a lamp - not ideal. I got the low-power blue LCD, and the jumper is in the appropriate 5V position. I tried the backlight pot, it doesn't change anything. I might've mishandled the LCD somehow and damaged it, but since the display part works, I figure it's worth trying to fix. So, do the excellent folks here have a clue how to test what works? where to test the LCD for what backlight current? Thanks! Edited May 21, 2010 by perplx Quote Link to comment Share on other sites More sharing options...
Wilba Posted May 20, 2010 Report Share Posted May 20, 2010 The white/blue LCDs just have one LED on the right side. I got a bunch of these LCDs cheap, but the LEDs were green. Don't ask me why they made such a yucky combo. Anyway, I just bought some white LEDs, took out the green LED and put in a white one. So what you can do is, test if the LED is working by itself, and also test if there is power going to the backlight pins of the LCD header (on the base). Testing LED is easy... just use a 5V supply through a resistor, anything between 100 ohm and 1K will be OK for this test. Disconnect the LCD from the base PCB (it can stay screwed into the CS PCB). Touch the wires onto the pins of the LED, where they are soldered to the LCD. You can also check it at the top two pins of the header, these pins would connect into the B+ and B- pins of the J16 header on the base PCB. You can test if the backlight pins on the base is working too. Make sure you have JBL set to 5V, and JR4 doesn't have a shunt. Stick a LED into the B+ and B- pins of the header. A spare LED that came with the kit is fine. Cathode (short lead) goes to B- pin. Most likely you have a bad solder joint somewhere, as I test each LCD before packing... but in the worst case scenario that the LED isn't working, I can send you a new white LED, it's pretty easy to replace... this is the main reason I chose to "recycle" these LCDs because they have easily fixable backlight LEDs and the replacement LED is a common 3mm LED. Quote Link to comment Share on other sites More sharing options...
perplx Posted May 21, 2010 Author Report Share Posted May 21, 2010 Thanks! The LCD wasn't to blame, putting an LED between B+ and B-, as you suggested, didn't show any light. I followed the traces and found one of the legs of the voltage-select jumper had a dodgy-looking joint; re-heated that and I got a soothing blue light from the LCD. So, my bad. :whistle: Thanks for the support! You rock so hard, it's kind of crazy. Quote Link to comment Share on other sites More sharing options...
Wilba Posted May 21, 2010 Report Share Posted May 21, 2010 POIDH! Good to hear it all works now. :D Quote Link to comment Share on other sites More sharing options...
rbv2 Posted February 5, 2014 Report Share Posted February 5, 2014 (edited) .. Edited February 5, 2014 by rbv2 Quote Link to comment Share on other sites More sharing options...
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