Buzzing LCD...

[Jidis]

Sorry for the rapid fire LCD posts ;D -

I've got an old Roland MIDI parametric EQ here which has always produced an audible hum while it was on (I bought it used). I've gotten my rooms quiet enough where it's not a very welcomed noise, but it looks too hi-tech not to keep turned on. ;)

Now that I know how common most of the standard screens and chipsets are, I thought about just finding an equivalent and swapping them. Has anyone here seen (heard) this problem in a screen and does it sound like a failure of something, or just an inherent flaw?

- It's an HD chipset, but not as common as the 44780. IIRC, the screen looks like a 4x20. It has three HD44102CH chips and is a Sharp LMO9601 (I think)

                                                            -George

[raphael]

Has anyone here seen (heard) this problem in a screen and does it sound like a failure of something, or just an inherent flaw?

Never seen/heard ;D a humming LCD. I'd bet it`s the transformer!

Raphael

[Jidis]

That's what I had always figured too. A few days ago I finally decided to put an ear to it and try to pinpoint the source, and ultimately ended up tearing it apart to verify it.

It's not the greatest looking display in the world anyway. It's always looked sort of dim and hard to read. Maybe the backlight isn't 100% up to spec. Either way, I wouldn't cry if it was replaced.

                                                                 - George

PS- The kind souls at Roland also put the contrast pot on the back of the chassis, and this unit is two rackspaces, about 20" deep and weighs as much as one of those rackmount ATX cases. :o

[Screaming_Rabbit]

I bet it's the backlight inverter... had that same problem on a 10" TFT

Greets, Roger

[Jidis]

That sounds right :(

I was looking at it again last night before I threw it back together. It looks like the backlight isn't even working correctly. You have to cup your hands over the screen to even tell that it's lit. I may try disconnecting it when I get a chance. The thing's got something like 21 leads going to it.

                                                                 -Thanks!

George

[moebius]

The EL backlight should have only two contacts .

[Jidis]

Yeah, there are two big solder globs on the edge of the board for it. They just trace over to two of the 21 pin row (hardwired to one of the main boards).

Can you manually light any of these things from the side or with a replacement light? Pinouts are about the only thing I've ever had to learn about LCD's.

-George

[titan]

Some weeks ago i bought a CASIO watch, and when you put your ear close you can hear that humming. In  the manual they write that this sound is absolutely normal for this kind of illumination(?CCFL?)

[SMIDIRIN]

Hi Jidis,

>Can you manually light any of these things from the side or with a replacement light? Pinouts are about the only thing I've ever had to learn about LCD's

if it's EL sometimes you can replace the EL FOIL..which may or may not be easy to get at..i got some from ebay and it was easy stuff to install (in my case)

S

[Jidis]

Thanks! (and SMIDIRIN, thanks for the luminance reply too)

There was a metal cover holding the main glass lens on the buzzing LCD. It didn't look that hard to take off. It's just got those flat metal tabs that they push through slots on a PCB or something and twist them a bit on the other side. I may look into the foil replacement, but I don't know how much time this unit is worth. It's only a minor annoyance. The EQ itself is built like a tank (or a 16bit version of a tank). I've got an old Mix magazine where they reviewed it and it was a few grand or something way back then and may have even been used in some mastering, so it probably didn't have the buzz when it was new. I never got enough use out of it to notice when the noise showed up.

                                                          -Take Care

George