Heat problems

[ribo]

i have a 20x4 backlit LCD, and i noticed that it got pretty warm.
after leaving my computer/LCD on over night, i noticed that there were several burn marks on the lower part of the PCB and the thick (what looks like to be a ground wire) has asctually come off of the PCB. The LCD still works fine and so does the backlight, and i am not interested in returning it. However, since this happened outside my case, (an i live in Washington state so ambient temp is no problem) i just think that this is a serious issue that needs to be addressed.

-ribo

[CF Tech]

ribo:

Did you make your own cable? If so please verify that the LED+ is connected to +5v (red wire) and not the +12v (yellow wire) -- that could cook things pretty well.

Please contact orders@crystalfontz.com to have your display replaced.

Leaving the backlight on continuously should not cause any of the symptoms you have described.

[ribo]

nope got both of the cables direct from you

[rupert]

Hi ribo,

If you have a multimeter, you may want to try connecting it up to the +5v lines that the Crystalfontz backlight cable is connected with, and try measuring the DC voltage for a couple of minutes. Check to make sure that it's actually around +5v or so (minor fluctations such as 5.1 aren't an issue). This should at least help eliminate any problems or instability you might be having with your computer power supply.

Is there a chance that something conductive (e.g. case metal) might have come in contact with the solder side of the PCB and have caused it to short?

Good luck,

--- Rupert Scammell
rupe@metro.yak.net
http://metro.yak.net

[ribo]

ya i think i will try that. the voltimeter embedded in my mobo says 5v though and the PSU was pretty hi-quality, but you never know...

but i have pumped to much v through a LED before and it just died so i thinking that may not be the problem, but CFZ may have made some sort of protection from that sort of thing... (mabye thick hi-ferad wire that heats up

[rupert]

The 634 has no over-voltage circuitry that I know of. I was unfortunate (and unwise enough) to accidentally connect my first 634 display to the 12v leads of my supply during some experiments. It actually ran for about 5 minutes before the backlight cut out. Surprisingly, the serial output continued to work without a hitch, but the backlight was no more...

It continues to function (albeit w/o backlight), which is pretty impressive.

I'll be more careful splicing cables in the future.

Incidentally, I'd like to propose a slight modification to the CrystalFontz backlight cable. Since people often have power cables at a premium inside their cases, it'd be cool if the cable could emulate the style of cable used by the cooling fans on processor heatsinks, and have a male connector that connects to the power supply leads, with a 4 lead female Molex connector chained out the top along with the two 5v leads to the backlight. This would prevent you from losing a power connector to the backlight...

Sincerely,

--- Rupert Scammell
rupe@metro.yak.net
http://metro.yak.net

[ribo]

yea i think that hooking it up to the little 3 pin molexes would be a better plan, but unless they fix the heat problem (mabye jus on mine) it would seem that there is a lot of wattage going through that wire (causing the heatup and wire meltiness). and it would really suck if it decided to pull too much wattage thru the mobo...

i would rather fry the LCD than my motherboard

mabye i will do what i do with everything that overheats in my system... water-cool it!!

i included a pic this is where i am talking about it is brown and the wire came off the PCB

(yes!! MS Paint action )

[ribo]

[CF Tech]

The area you indicate does have a trace on each side that is related to the backlight.

The 634 backlight should draw about 525mA. Are you able to measure the current through the backlight on the display? Does that trace get noticeably hot when the LCD is operating?

I was thinking about your situation, and decided to try a test. I took a PCB from a 634 and put a jumper where the backlight would be, so I could force current from LED+ up to where the LED backlight would be, and then back to ground through the traces that would normally feed the backlight.

I fed 3000mA through the traces for about 30 minutes. The traces did get hot--too hot to comfortably keep your finger on them, but not hot enough to sizzle--so they were probably on the order of around 200 deg F. There was no sign of discoloration. I would not expect any discoloration since the PCB is made to handle solder that typically is applied with a soldering a iron set at 500 to 700 degrees.

I can only think of two ways that the trace on your board got that hot. The first possibility would be if the trace was abnormally thin--not particularly likely, but possible. The second would be if something touched (shorted) the trace to ground when the power was applied. With the high currents that modern PC power supplies are capable of, that could smoke the trace in a short amount of time.

Just some thoughts. The offer still stands if you want to swap the display out with a replacement.

[ribo]

i agree with you there, the PCB should be able to handle some heat.

but.... now that i realize what i might do with the LCD, i think i want to get it replaced...

what would i have to do in order to return it?

PS I bought this off of one of my friends (unused / still in pkg) does that void any kind of warrantee and it means i don't have any kind of receipt?

PPS I am looking for a exchange not a refund if that changes anything

[CF Tech]

Please write orders@crystalfontz.com to arrange a return.

If possible, please supply the original purchaser's name.

[edd91]

CF i was thinking mabye an actual deformation in the PCB which gets affected by certain things, mabye the PCB doesnt like voltage in it, or whatever he is resting the drive on is affected it